feat(users/kranzes): add wasm-hello-world r/8338

This can be used as a reference for how to build a wasm project with
crate2nix.

Change-Id: Ib4d0db6bf24d8f1dec4734d5f1e8de19212a54cd
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11859
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

7 files changed, 1262 insertions, 0 deletions

diff --git a/users/kranzes/OWNERS b/users/kranzes/OWNERS
new file mode 100644
index 000000000000..7c5803bf4150
--- /dev/null
+++ b/users/kranzes/OWNERS
@@ -0,0 +1 @@
+kranzes
diff --git a/users/kranzes/wasm-hello-world/Cargo.lock b/users/kranzes/wasm-hello-world/Cargo.lock
new file mode 100644
index 000000000000..d0ad9e38d78c
--- /dev/null
+++ b/users/kranzes/wasm-hello-world/Cargo.lock
@@ -0,0 +1,123 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "bumpalo"
+version = "3.16.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "79296716171880943b8470b5f8d03aa55eb2e645a4874bdbb28adb49162e012c"
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "log"
+version = "0.4.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "90ed8c1e510134f979dbc4f070f87d4313098b704861a105fe34231c70a3901c"
+
+[[package]]
+name = "once_cell"
+version = "1.19.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3fdb12b2476b595f9358c5161aa467c2438859caa136dec86c26fdd2efe17b92"
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.85"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22244ce15aa966053a896d1accb3a6e68469b97c7f33f284b99f0d576879fc23"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.36"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0fa76aaf39101c457836aec0ce2316dbdc3ab723cdda1c6bd4e6ad4208acaca7"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.66"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c42f3f41a2de00b01c0aaad383c5a45241efc8b2d1eda5661812fda5f3cdcff5"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3354b9ac3fae1ff6755cb6db53683adb661634f67557942dea4facebec0fee4b"
+
+[[package]]
+name = "wasm-bindgen"
+version = "0.2.92"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4be2531df63900aeb2bca0daaaddec08491ee64ceecbee5076636a3b026795a8"
+dependencies = [
+ "cfg-if",
+ "wasm-bindgen-macro",
+]
+
+[[package]]
+name = "wasm-bindgen-backend"
+version = "0.2.92"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "614d787b966d3989fa7bb98a654e369c762374fd3213d212cfc0251257e747da"
+dependencies = [
+ "bumpalo",
+ "log",
+ "once_cell",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "wasm-bindgen-shared",
+]
+
+[[package]]
+name = "wasm-bindgen-macro"
+version = "0.2.92"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1f8823de937b71b9460c0c34e25f3da88250760bec0ebac694b49997550d726"
+dependencies = [
+ "quote",
+ "wasm-bindgen-macro-support",
+]
+
+[[package]]
+name = "wasm-bindgen-macro-support"
+version = "0.2.92"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e94f17b526d0a461a191c78ea52bbce64071ed5c04c9ffe424dcb38f74171bb7"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+ "wasm-bindgen-backend",
+ "wasm-bindgen-shared",
+]
+
+[[package]]
+name = "wasm-bindgen-shared"
+version = "0.2.92"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "af190c94f2773fdb3729c55b007a722abb5384da03bc0986df4c289bf5567e96"
+
+[[package]]
+name = "wasm_hello_world"
+version = "0.1.0"
+dependencies = [
+ "wasm-bindgen",
+]
diff --git a/users/kranzes/wasm-hello-world/Cargo.nix b/users/kranzes/wasm-hello-world/Cargo.nix
new file mode 100644
index 000000000000..2f629a04d6e7
--- /dev/null
+++ b/users/kranzes/wasm-hello-world/Cargo.nix
@@ -0,0 +1,1083 @@
+# This file was @generated by crate2nix 0.14.1 with the command:
+#   "generate" "--all-features"
+# See https://github.com/kolloch/crate2nix for more info.
+
+{ nixpkgs ? <nixpkgs>
+, pkgs ? import nixpkgs { config = { }; }
+, lib ? pkgs.lib
+, stdenv ? pkgs.stdenv
+, buildRustCrateForPkgs ? pkgs: pkgs.buildRustCrate
+  # This is used as the `crateOverrides` argument for `buildRustCrate`.
+, defaultCrateOverrides ? pkgs.defaultCrateOverrides
+  # The features to enable for the root_crate or the workspace_members.
+, rootFeatures ? [ "default" ]
+  # If true, throw errors instead of issueing deprecation warnings.
+, strictDeprecation ? false
+  # Elements to add to the `-C target-feature=` argument passed to `rustc`
+  # (separated by `,`, prefixed with `+`).
+  # Used for conditional compilation based on CPU feature detection.
+, targetFeatures ? [ ]
+  # Whether to perform release builds: longer compile times, faster binaries.
+, release ? true
+  # Additional crate2nix configuration if it exists.
+, crateConfig ? if builtins.pathExists ./crate-config.nix
+  then pkgs.callPackage ./crate-config.nix { }
+  else { }
+}:
+
+rec {
+  #
+  # "public" attributes that we attempt to keep stable with new versions of crate2nix.
+  #
+
+  rootCrate = rec {
+    packageId = "wasm_hello_world";
+
+    # Use this attribute to refer to the derivation building your root crate package.
+    # You can override the features with rootCrate.build.override { features = [ "default" "feature1" ... ]; }.
+    build = internal.buildRustCrateWithFeatures {
+      inherit packageId;
+    };
+
+    # Debug support which might change between releases.
+    # File a bug if you depend on any for non-debug work!
+    debug = internal.debugCrate { inherit packageId; };
+  };
+  # Refer your crate build derivation by name here.
+  # You can override the features with
+  # workspaceMembers."${crateName}".build.override { features = [ "default" "feature1" ... ]; }.
+  workspaceMembers = {
+    "wasm_hello_world" = rec {
+      packageId = "wasm_hello_world";
+      build = internal.buildRustCrateWithFeatures {
+        packageId = "wasm_hello_world";
+      };
+
+      # Debug support which might change between releases.
+      # File a bug if you depend on any for non-debug work!
+      debug = internal.debugCrate { inherit packageId; };
+    };
+  };
+
+  # A derivation that joins the outputs of all workspace members together.
+  allWorkspaceMembers = pkgs.symlinkJoin {
+    name = "all-workspace-members";
+    paths =
+      let members = builtins.attrValues workspaceMembers;
+      in builtins.map (m: m.build) members;
+  };
+
+  #
+  # "internal" ("private") attributes that may change in every new version of crate2nix.
+  #
+
+  internal = rec {
+    # Build and dependency information for crates.
+    # Many of the fields are passed one-to-one to buildRustCrate.
+    #
+    # Noteworthy:
+    # * `dependencies`/`buildDependencies`: similar to the corresponding fields for buildRustCrate.
+    #   but with additional information which is used during dependency/feature resolution.
+    # * `resolvedDependencies`: the selected default features reported by cargo - only included for debugging.
+    # * `devDependencies` as of now not used by `buildRustCrate` but used to
+    #   inject test dependencies into the build
+
+    crates = {
+      "bumpalo" = rec {
+        crateName = "bumpalo";
+        version = "3.16.0";
+        edition = "2021";
+        sha256 = "0b015qb4knwanbdlp1x48pkb4pm57b8gidbhhhxr900q2wb6fabr";
+        authors = [
+          "Nick Fitzgerald <fitzgen@gmail.com>"
+        ];
+        features = {
+          "allocator-api2" = [ "dep:allocator-api2" ];
+          "serde" = [ "dep:serde" ];
+        };
+        resolvedDefaultFeatures = [ "default" ];
+      };
+      "cfg-if" = rec {
+        crateName = "cfg-if";
+        version = "1.0.0";
+        edition = "2018";
+        sha256 = "1za0vb97n4brpzpv8lsbnzmq5r8f2b0cpqqr0sy8h5bn751xxwds";
+        authors = [
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        features = {
+          "compiler_builtins" = [ "dep:compiler_builtins" ];
+          "core" = [ "dep:core" ];
+          "rustc-dep-of-std" = [ "core" "compiler_builtins" ];
+        };
+      };
+      "log" = rec {
+        crateName = "log";
+        version = "0.4.21";
+        edition = "2021";
+        sha256 = "074hldq1q8rlzq2s2qa8f25hj4s3gpw71w64vdwzjd01a4g8rvch";
+        authors = [
+          "The Rust Project Developers"
+        ];
+        features = {
+          "kv_serde" = [ "kv_std" "value-bag/serde" "serde" ];
+          "kv_std" = [ "std" "kv" "value-bag/error" ];
+          "kv_sval" = [ "kv" "value-bag/sval" "sval" "sval_ref" ];
+          "kv_unstable" = [ "kv" "value-bag" ];
+          "kv_unstable_serde" = [ "kv_serde" "kv_unstable_std" ];
+          "kv_unstable_std" = [ "kv_std" "kv_unstable" ];
+          "kv_unstable_sval" = [ "kv_sval" "kv_unstable" ];
+          "serde" = [ "dep:serde" ];
+          "sval" = [ "dep:sval" ];
+          "sval_ref" = [ "dep:sval_ref" ];
+          "value-bag" = [ "dep:value-bag" ];
+        };
+      };
+      "once_cell" = rec {
+        crateName = "once_cell";
+        version = "1.19.0";
+        edition = "2021";
+        sha256 = "14kvw7px5z96dk4dwdm1r9cqhhy2cyj1l5n5b29mynbb8yr15nrz";
+        authors = [
+          "Aleksey Kladov <aleksey.kladov@gmail.com>"
+        ];
+        features = {
+          "alloc" = [ "race" ];
+          "atomic-polyfill" = [ "critical-section" ];
+          "critical-section" = [ "dep:critical-section" "portable-atomic" ];
+          "default" = [ "std" ];
+          "parking_lot" = [ "dep:parking_lot_core" ];
+          "portable-atomic" = [ "dep:portable-atomic" ];
+          "std" = [ "alloc" ];
+        };
+        resolvedDefaultFeatures = [ "alloc" "default" "race" "std" ];
+      };
+      "proc-macro2" = rec {
+        crateName = "proc-macro2";
+        version = "1.0.85";
+        edition = "2021";
+        sha256 = "08zwg5l5f3czp62g4cvzgjwnk176lsrwq6kdi4x0arm9bbhlq912";
+        libName = "proc_macro2";
+        authors = [
+          "David Tolnay <dtolnay@gmail.com>"
+          "Alex Crichton <alex@alexcrichton.com>"
+        ];
+        dependencies = [
+          {
+            name = "unicode-ident";
+            packageId = "unicode-ident";
+          }
+        ];
+        features = {
+          "default" = [ "proc-macro" ];
+        };
+        resolvedDefaultFeatures = [ "default" "proc-macro" ];
+      };
+      "quote" = rec {
+        crateName = "quote";
+        version = "1.0.36";
+        edition = "2018";
+        sha256 = "19xcmh445bg6simirnnd4fvkmp6v2qiwxh5f6rw4a70h76pnm9qg";
+        authors = [
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "proc-macro2";
+            packageId = "proc-macro2";
+            usesDefaultFeatures = false;
+          }
+        ];
+        features = {
+          "default" = [ "proc-macro" ];
+          "proc-macro" = [ "proc-macro2/proc-macro" ];
+        };
+        resolvedDefaultFeatures = [ "default" "proc-macro" ];
+      };
+      "syn" = rec {
+        crateName = "syn";
+        version = "2.0.66";
+        edition = "2021";
+        sha256 = "1xfgrprsbz8j31kabvfinb4fyhajlk2q7lxa18fb006yl90kyby4";
+        authors = [
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+        dependencies = [
+          {
+            name = "proc-macro2";
+            packageId = "proc-macro2";
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "quote";
+            packageId = "quote";
+            optional = true;
+            usesDefaultFeatures = false;
+          }
+          {
+            name = "unicode-ident";
+            packageId = "unicode-ident";
+          }
+        ];
+        features = {
+          "default" = [ "derive" "parsing" "printing" "clone-impls" "proc-macro" ];
+          "printing" = [ "dep:quote" ];
+          "proc-macro" = [ "proc-macro2/proc-macro" "quote?/proc-macro" ];
+          "test" = [ "syn-test-suite/all-features" ];
+        };
+        resolvedDefaultFeatures = [ "clone-impls" "default" "derive" "full" "parsing" "printing" "proc-macro" "visit" ];
+      };
+      "unicode-ident" = rec {
+        crateName = "unicode-ident";
+        version = "1.0.12";
+        edition = "2018";
+        sha256 = "0jzf1znfpb2gx8nr8mvmyqs1crnv79l57nxnbiszc7xf7ynbjm1k";
+        authors = [
+          "David Tolnay <dtolnay@gmail.com>"
+        ];
+
+      };
+      "wasm-bindgen" = rec {
+        crateName = "wasm-bindgen";
+        version = "0.2.92";
+        edition = "2018";
+        sha256 = "1a4mcw13nsk3fr8fxjzf9kk1wj88xkfsmnm0pjraw01ryqfm7qjb";
+        authors = [
+          "The wasm-bindgen Developers"
+        ];
+        dependencies = [
+          {
+            name = "cfg-if";
+            packageId = "cfg-if";
+          }
+          {
+            name = "wasm-bindgen-macro";
+            packageId = "wasm-bindgen-macro";
+          }
+        ];
+        features = {
+          "default" = [ "spans" "std" ];
+          "enable-interning" = [ "std" ];
+          "gg-alloc" = [ "wasm-bindgen-test/gg-alloc" ];
+          "serde" = [ "dep:serde" ];
+          "serde-serialize" = [ "serde" "serde_json" "std" ];
+          "serde_json" = [ "dep:serde_json" ];
+          "spans" = [ "wasm-bindgen-macro/spans" ];
+          "strict-macro" = [ "wasm-bindgen-macro/strict-macro" ];
+          "xxx_debug_only_print_generated_code" = [ "wasm-bindgen-macro/xxx_debug_only_print_generated_code" ];
+        };
+        resolvedDefaultFeatures = [ "default" "spans" "std" ];
+      };
+      "wasm-bindgen-backend" = rec {
+        crateName = "wasm-bindgen-backend";
+        version = "0.2.92";
+        edition = "2018";
+        sha256 = "1nj7wxbi49f0rw9d44rjzms26xlw6r76b2mrggx8jfbdjrxphkb1";
+        authors = [
+          "The wasm-bindgen Developers"
+        ];
+        dependencies = [
+          {
+            name = "bumpalo";
+            packageId = "bumpalo";
+          }
+          {
+            name = "log";
+            packageId = "log";
+          }
+          {
+            name = "once_cell";
+            packageId = "once_cell";
+          }
+          {
+            name = "proc-macro2";
+            packageId = "proc-macro2";
+          }
+          {
+            name = "quote";
+            packageId = "quote";
+          }
+          {
+            name = "syn";
+            packageId = "syn";
+            features = [ "full" ];
+          }
+          {
+            name = "wasm-bindgen-shared";
+            packageId = "wasm-bindgen-shared";
+          }
+        ];
+        features = {
+          "extra-traits" = [ "syn/extra-traits" ];
+        };
+        resolvedDefaultFeatures = [ "spans" ];
+      };
+      "wasm-bindgen-macro" = rec {
+        crateName = "wasm-bindgen-macro";
+        version = "0.2.92";
+        edition = "2018";
+        sha256 = "09npa1srjjabd6nfph5yc03jb26sycjlxhy0c2a1pdrpx4yq5y51";
+        procMacro = true;
+        authors = [
+          "The wasm-bindgen Developers"
+        ];
+        dependencies = [
+          {
+            name = "quote";
+            packageId = "quote";
+          }
+          {
+            name = "wasm-bindgen-macro-support";
+            packageId = "wasm-bindgen-macro-support";
+          }
+        ];
+        features = {
+          "spans" = [ "wasm-bindgen-macro-support/spans" ];
+          "strict-macro" = [ "wasm-bindgen-macro-support/strict-macro" ];
+        };
+        resolvedDefaultFeatures = [ "spans" ];
+      };
+      "wasm-bindgen-macro-support" = rec {
+        crateName = "wasm-bindgen-macro-support";
+        version = "0.2.92";
+        edition = "2018";
+        sha256 = "1dqv2xs8zcyw4kjgzj84bknp2h76phmsb3n7j6hn396h4ssifkz9";
+        authors = [
+          "The wasm-bindgen Developers"
+        ];
+        dependencies = [
+          {
+            name = "proc-macro2";
+            packageId = "proc-macro2";
+          }
+          {
+            name = "quote";
+            packageId = "quote";
+          }
+          {
+            name = "syn";
+            packageId = "syn";
+            features = [ "visit" "full" ];
+          }
+          {
+            name = "wasm-bindgen-backend";
+            packageId = "wasm-bindgen-backend";
+          }
+          {
+            name = "wasm-bindgen-shared";
+            packageId = "wasm-bindgen-shared";
+          }
+        ];
+        features = {
+          "extra-traits" = [ "syn/extra-traits" ];
+          "spans" = [ "wasm-bindgen-backend/spans" ];
+        };
+        resolvedDefaultFeatures = [ "spans" ];
+      };
+      "wasm-bindgen-shared" = rec {
+        crateName = "wasm-bindgen-shared";
+        version = "0.2.92";
+        edition = "2018";
+        links = "wasm_bindgen";
+        sha256 = "15kyavsrna2cvy30kg03va257fraf9x00ny554vxngvpyaa0q6dg";
+        authors = [
+          "The wasm-bindgen Developers"
+        ];
+
+      };
+      "wasm_hello_world" = rec {
+        crateName = "wasm_hello_world";
+        version = "0.1.0";
+        edition = "2021";
+        src = lib.cleanSourceWith { filter = sourceFilter; src = ./.; };
+        type = [ "cdylib" ];
+        dependencies = [
+          {
+            name = "wasm-bindgen";
+            packageId = "wasm-bindgen";
+          }
+        ];
+
+      };
+    };
+
+    #
+    # crate2nix/default.nix (excerpt start)
+    #
+
+    /* Target (platform) data for conditional dependencies.
+      This corresponds roughly to what buildRustCrate is setting.
+    */
+    makeDefaultTarget = platform: {
+      unix = platform.isUnix;
+      windows = platform.isWindows;
+      fuchsia = true;
+      test = false;
+
+      inherit (platform.rust.platform)
+        arch
+        os
+        vendor;
+      family = platform.rust.platform.target-family;
+      env = "gnu";
+      endian =
+        if platform.parsed.cpu.significantByte.name == "littleEndian"
+        then "little" else "big";
+      pointer_width = toString platform.parsed.cpu.bits;
+      debug_assertions = false;
+    };
+
+    /* Filters common temp files and build files. */
+    # TODO(pkolloch): Substitute with gitignore filter
+    sourceFilter = name: type:
+      let
+        baseName = builtins.baseNameOf (builtins.toString name);
+      in
+        ! (
+          # Filter out git
+          baseName == ".gitignore"
+          || (type == "directory" && baseName == ".git")
+
+          # Filter out build results
+          || (
+            type == "directory" && (
+              baseName == "target"
+              || baseName == "_site"
+              || baseName == ".sass-cache"
+              || baseName == ".jekyll-metadata"
+              || baseName == "build-artifacts"
+            )
+          )
+
+          # Filter out nix-build result symlinks
+          || (
+            type == "symlink" && lib.hasPrefix "result" baseName
+          )
+
+          # Filter out IDE config
+          || (
+            type == "directory" && (
+              baseName == ".idea" || baseName == ".vscode"
+            )
+          ) || lib.hasSuffix ".iml" baseName
+
+          # Filter out nix build files
+          || baseName == "Cargo.nix"
+
+          # Filter out editor backup / swap files.
+          || lib.hasSuffix "~" baseName
+          || builtins.match "^\\.sw[a-z]$$" baseName != null
+          || builtins.match "^\\..*\\.sw[a-z]$$" baseName != null
+          || lib.hasSuffix ".tmp" baseName
+          || lib.hasSuffix ".bak" baseName
+          || baseName == "tests.nix"
+        );
+
+    /* Returns a crate which depends on successful test execution
+      of crate given as the second argument.
+
+      testCrateFlags: list of flags to pass to the test exectuable
+      testInputs: list of packages that should be available during test execution
+    */
+    crateWithTest = { crate, testCrate, testCrateFlags, testInputs, testPreRun, testPostRun }:
+      assert builtins.typeOf testCrateFlags == "list";
+      assert builtins.typeOf testInputs == "list";
+      assert builtins.typeOf testPreRun == "string";
+      assert builtins.typeOf testPostRun == "string";
+      let
+        # override the `crate` so that it will build and execute tests instead of
+        # building the actual lib and bin targets We just have to pass `--test`
+        # to rustc and it will do the right thing.  We execute the tests and copy
+        # their log and the test executables to $out for later inspection.
+        test =
+          let
+            drv = testCrate.override
+              (
+                _: {
+                  buildTests = true;
+                  release = false;
+                }
+              );
+            # If the user hasn't set any pre/post commands, we don't want to
+            # insert empty lines. This means that any existing users of crate2nix
+            # don't get a spurious rebuild unless they set these explicitly.
+            testCommand = pkgs.lib.concatStringsSep "\n"
+              (pkgs.lib.filter (s: s != "") [
+                testPreRun
+                "$f $testCrateFlags 2>&1 | tee -a $out"
+                testPostRun
+              ]);
+          in
+          pkgs.runCommand "run-tests-${testCrate.name}"
+            {
+              inherit testCrateFlags;
+              buildInputs = testInputs;
+            } ''
+            set -e
+
+            export RUST_BACKTRACE=1
+
+            # recreate a file hierarchy as when running tests with cargo
+
+            # the source for test data
+            # It's necessary to locate the source in $NIX_BUILD_TOP/source/
+            # instead of $NIX_BUILD_TOP/
+            # because we compiled those test binaries in the former and not the latter.
+            # So all paths will expect source tree to be there and not in the build top directly.
+            # For example: $NIX_BUILD_TOP := /build in general, if you ask yourself.
+            # NOTE: There could be edge cases if `crate.sourceRoot` does exist but
+            # it's very hard to reason about them.
+            # Open a bug if you run into this!
+            mkdir -p source/
+            cd source/
+
+            ${pkgs.buildPackages.xorg.lndir}/bin/lndir ${crate.src}
+
+            # build outputs
+            testRoot=target/debug
+            mkdir -p $testRoot
+
+            # executables of the crate
+            # we copy to prevent std::env::current_exe() to resolve to a store location
+            for i in ${crate}/bin/*; do
+              cp "$i" "$testRoot"
+            done
+            chmod +w -R .
+
+            # test harness executables are suffixed with a hash, like cargo does
+            # this allows to prevent name collision with the main
+            # executables of the crate
+            hash=$(basename $out)
+            for file in ${drv}/tests/*; do
+              f=$testRoot/$(basename $file)-$hash
+              cp $file $f
+              ${testCommand}
+            done
+          '';
+      in
+      pkgs.runCommand "${crate.name}-linked"
+        {
+          inherit (crate) outputs crateName;
+          passthru = (crate.passthru or { }) // {
+            inherit test;
+          };
+        }
+        (lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform) ''
+          echo tested by ${test}
+        '' + ''
+          ${lib.concatMapStringsSep "\n" (output: "ln -s ${crate.${output}} ${"$"}${output}") crate.outputs}
+        '');
+
+    /* A restricted overridable version of builtRustCratesWithFeatures. */
+    buildRustCrateWithFeatures =
+      { packageId
+      , features ? rootFeatures
+      , crateOverrides ? defaultCrateOverrides
+      , buildRustCrateForPkgsFunc ? null
+      , runTests ? false
+      , testCrateFlags ? [ ]
+      , testInputs ? [ ]
+        # Any command to run immediatelly before a test is executed.
+      , testPreRun ? ""
+        # Any command run immediatelly after a test is executed.
+      , testPostRun ? ""
+      }:
+      lib.makeOverridable
+        (
+          { features
+          , crateOverrides
+          , runTests
+          , testCrateFlags
+          , testInputs
+          , testPreRun
+          , testPostRun
+          }:
+          let
+            buildRustCrateForPkgsFuncOverriden =
+              if buildRustCrateForPkgsFunc != null
+              then buildRustCrateForPkgsFunc
+              else
+                (
+                  if crateOverrides == pkgs.defaultCrateOverrides
+                  then buildRustCrateForPkgs
+                  else
+                    pkgs: (buildRustCrateForPkgs pkgs).override {
+                      defaultCrateOverrides = crateOverrides;
+                    }
+                );
+            builtRustCrates = builtRustCratesWithFeatures {
+              inherit packageId features;
+              buildRustCrateForPkgsFunc = buildRustCrateForPkgsFuncOverriden;
+              runTests = false;
+            };
+            builtTestRustCrates = builtRustCratesWithFeatures {
+              inherit packageId features;
+              buildRustCrateForPkgsFunc = buildRustCrateForPkgsFuncOverriden;
+              runTests = true;
+            };
+            drv = builtRustCrates.crates.${packageId};
+            testDrv = builtTestRustCrates.crates.${packageId};
+            derivation =
+              if runTests then
+                crateWithTest
+                  {
+                    crate = drv;
+                    testCrate = testDrv;
+                    inherit testCrateFlags testInputs testPreRun testPostRun;
+                  }
+              else drv;
+          in
+          derivation
+        )
+        { inherit features crateOverrides runTests testCrateFlags testInputs testPreRun testPostRun; };
+
+    /* Returns an attr set with packageId mapped to the result of buildRustCrateForPkgsFunc
+      for the corresponding crate.
+    */
+    builtRustCratesWithFeatures =
+      { packageId
+      , features
+      , crateConfigs ? crates
+      , buildRustCrateForPkgsFunc
+      , runTests
+      , makeTarget ? makeDefaultTarget
+      } @ args:
+        assert (builtins.isAttrs crateConfigs);
+        assert (builtins.isString packageId);
+        assert (builtins.isList features);
+        assert (builtins.isAttrs (makeTarget stdenv.hostPlatform));
+        assert (builtins.isBool runTests);
+        let
+          rootPackageId = packageId;
+          mergedFeatures = mergePackageFeatures
+            (
+              args // {
+                inherit rootPackageId;
+                target = makeTarget stdenv.hostPlatform // { test = runTests; };
+              }
+            );
+          # Memoize built packages so that reappearing packages are only built once.
+          builtByPackageIdByPkgs = mkBuiltByPackageIdByPkgs pkgs;
+          mkBuiltByPackageIdByPkgs = pkgs:
+            let
+              self = {
+                crates = lib.mapAttrs (packageId: value: buildByPackageIdForPkgsImpl self pkgs packageId) crateConfigs;
+                target = makeTarget stdenv.hostPlatform;
+                build = mkBuiltByPackageIdByPkgs pkgs.buildPackages;
+              };
+            in
+            self;
+          buildByPackageIdForPkgsImpl = self: pkgs: packageId:
+            let
+              features = mergedFeatures."${packageId}" or [ ];
+              crateConfig' = crateConfigs."${packageId}";
+              crateConfig =
+                builtins.removeAttrs crateConfig' [ "resolvedDefaultFeatures" "devDependencies" ];
+              devDependencies =
+                lib.optionals
+                  (runTests && packageId == rootPackageId)
+                  (crateConfig'.devDependencies or [ ]);
+              dependencies =
+                dependencyDerivations {
+                  inherit features;
+                  inherit (self) target;
+                  buildByPackageId = depPackageId:
+                    # proc_macro crates must be compiled for the build architecture
+                    if crateConfigs.${depPackageId}.procMacro or false
+                    then self.build.crates.${depPackageId}
+                    else self.crates.${depPackageId};
+                  dependencies =
+                    (crateConfig.dependencies or [ ])
+                    ++ devDependencies;
+                };
+              buildDependencies =
+                dependencyDerivations {
+                  inherit features;
+                  inherit (self.build) target;
+                  buildByPackageId = depPackageId:
+                    self.build.crates.${depPackageId};
+                  dependencies = crateConfig.buildDependencies or [ ];
+                };
+              dependenciesWithRenames =
+                let
+                  buildDeps = filterEnabledDependencies {
+                    inherit features;
+                    inherit (self) target;
+                    dependencies = crateConfig.dependencies or [ ] ++ devDependencies;
+                  };
+                  hostDeps = filterEnabledDependencies {
+                    inherit features;
+                    inherit (self.build) target;
+                    dependencies = crateConfig.buildDependencies or [ ];
+                  };
+                in
+                lib.filter (d: d ? "rename") (hostDeps ++ buildDeps);
+              # Crate renames have the form:
+              #
+              # {
+              #    crate_name = [
+              #       { version = "1.2.3"; rename = "crate_name01"; }
+              #    ];
+              #    # ...
+              # }
+              crateRenames =
+                let
+                  grouped =
+                    lib.groupBy
+                      (dependency: dependency.name)
+                      dependenciesWithRenames;
+                  versionAndRename = dep:
+                    let
+                      package = crateConfigs."${dep.packageId}";
+                    in
+                    { inherit (dep) rename; inherit (package) version; };
+                in
+                lib.mapAttrs (name: builtins.map versionAndRename) grouped;
+            in
+            buildRustCrateForPkgsFunc pkgs
+              (
+                crateConfig // {
+                  src = crateConfig.src or (
+                    pkgs.fetchurl rec {
+                      name = "${crateConfig.crateName}-${crateConfig.version}.tar.gz";
+                      # https://www.pietroalbini.org/blog/downloading-crates-io/
+                      # Not rate-limited, CDN URL.
+                      url = "https://static.crates.io/crates/${crateConfig.crateName}/${crateConfig.crateName}-${crateConfig.version}.crate";
+                      sha256 =
+                        assert (lib.assertMsg (crateConfig ? sha256) "Missing sha256 for ${name}");
+                        crateConfig.sha256;
+                    }
+                  );
+                  extraRustcOpts = lib.lists.optional (targetFeatures != [ ]) "-C target-feature=${lib.concatMapStringsSep "," (x: "+${x}") targetFeatures}";
+                  inherit features dependencies buildDependencies crateRenames release;
+                }
+              );
+        in
+        builtByPackageIdByPkgs;
+
+    /* Returns the actual derivations for the given dependencies. */
+    dependencyDerivations =
+      { buildByPackageId
+      , features
+      , dependencies
+      , target
+      }:
+        assert (builtins.isList features);
+        assert (builtins.isList dependencies);
+        assert (builtins.isAttrs target);
+        let
+          enabledDependencies = filterEnabledDependencies {
+            inherit dependencies features target;
+          };
+          depDerivation = dependency: buildByPackageId dependency.packageId;
+        in
+        map depDerivation enabledDependencies;
+
+    /* Returns a sanitized version of val with all values substituted that cannot
+      be serialized as JSON.
+    */
+    sanitizeForJson = val:
+      if builtins.isAttrs val
+      then lib.mapAttrs (n: sanitizeForJson) val
+      else if builtins.isList val
+      then builtins.map sanitizeForJson val
+      else if builtins.isFunction val
+      then "function"
+      else val;
+
+    /* Returns various tools to debug a crate. */
+    debugCrate = { packageId, target ? makeDefaultTarget stdenv.hostPlatform }:
+      assert (builtins.isString packageId);
+      let
+        debug = rec {
+          # The built tree as passed to buildRustCrate.
+          buildTree = buildRustCrateWithFeatures {
+            buildRustCrateForPkgsFunc = _: lib.id;
+            inherit packageId;
+          };
+          sanitizedBuildTree = sanitizeForJson buildTree;
+          dependencyTree = sanitizeForJson
+            (
+              buildRustCrateWithFeatures {
+                buildRustCrateForPkgsFunc = _: crate: {
+                  "01_crateName" = crate.crateName or false;
+                  "02_features" = crate.features or [ ];
+                  "03_dependencies" = crate.dependencies or [ ];
+                };
+                inherit packageId;
+              }
+            );
+          mergedPackageFeatures = mergePackageFeatures {
+            features = rootFeatures;
+            inherit packageId target;
+          };
+          diffedDefaultPackageFeatures = diffDefaultPackageFeatures {
+            inherit packageId target;
+          };
+        };
+      in
+      { internal = debug; };
+
+    /* Returns differences between cargo default features and crate2nix default
+      features.
+
+      This is useful for verifying the feature resolution in crate2nix.
+    */
+    diffDefaultPackageFeatures =
+      { crateConfigs ? crates
+      , packageId
+      , target
+      }:
+        assert (builtins.isAttrs crateConfigs);
+        let
+          prefixValues = prefix: lib.mapAttrs (n: v: { "${prefix}" = v; });
+          mergedFeatures =
+            prefixValues
+              "crate2nix"
+              (mergePackageFeatures { inherit crateConfigs packageId target; features = [ "default" ]; });
+          configs = prefixValues "cargo" crateConfigs;
+          combined = lib.foldAttrs (a: b: a // b) { } [ mergedFeatures configs ];
+          onlyInCargo =
+            builtins.attrNames
+              (lib.filterAttrs (n: v: !(v ? "crate2nix") && (v ? "cargo")) combined);
+          onlyInCrate2Nix =
+            builtins.attrNames
+              (lib.filterAttrs (n: v: (v ? "crate2nix") && !(v ? "cargo")) combined);
+          differentFeatures = lib.filterAttrs
+            (
+              n: v:
+                (v ? "crate2nix")
+                && (v ? "cargo")
+                && (v.crate2nix.features or [ ]) != (v."cargo".resolved_default_features or [ ])
+            )
+            combined;
+        in
+        builtins.toJSON {
+          inherit onlyInCargo onlyInCrate2Nix differentFeatures;
+        };
+
+    /* Returns an attrset mapping packageId to the list of enabled features.
+
+      If multiple paths to a dependency enable different features, the
+      corresponding feature sets are merged. Features in rust are additive.
+    */
+    mergePackageFeatures =
+      { crateConfigs ? crates
+      , packageId
+      , rootPackageId ? packageId
+      , features ? rootFeatures
+      , dependencyPath ? [ crates.${packageId}.crateName ]
+      , featuresByPackageId ? { }
+      , target
+        # Adds devDependencies to the crate with rootPackageId.
+      , runTests ? false
+      , ...
+      } @ args:
+        assert (builtins.isAttrs crateConfigs);
+        assert (builtins.isString packageId);
+        assert (builtins.isString rootPackageId);
+        assert (builtins.isList features);
+        assert (builtins.isList dependencyPath);
+        assert (builtins.isAttrs featuresByPackageId);
+        assert (builtins.isAttrs target);
+        assert (builtins.isBool runTests);
+        let
+          crateConfig = crateConfigs."${packageId}" or (builtins.throw "Package not found: ${packageId}");
+          expandedFeatures = expandFeatures (crateConfig.features or { }) features;
+          enabledFeatures = enableFeatures (crateConfig.dependencies or [ ]) expandedFeatures;
+          depWithResolvedFeatures = dependency:
+            let
+              inherit (dependency) packageId;
+              features = dependencyFeatures enabledFeatures dependency;
+            in
+            { inherit packageId features; };
+          resolveDependencies = cache: path: dependencies:
+            assert (builtins.isAttrs cache);
+            assert (builtins.isList dependencies);
+            let
+              enabledDependencies = filterEnabledDependencies {
+                inherit dependencies target;
+                features = enabledFeatures;
+              };
+              directDependencies = map depWithResolvedFeatures enabledDependencies;
+              foldOverCache = op: lib.foldl op cache directDependencies;
+            in
+            foldOverCache
+              (
+                cache: { packageId, features }:
+                  let
+                    cacheFeatures = cache.${packageId} or [ ];
+                    combinedFeatures = sortedUnique (cacheFeatures ++ features);
+                  in
+                  if cache ? ${packageId} && cache.${packageId} == combinedFeatures
+                  then cache
+                  else
+                    mergePackageFeatures {
+                      features = combinedFeatures;
+                      featuresByPackageId = cache;
+                      inherit crateConfigs packageId target runTests rootPackageId;
+                    }
+              );
+          cacheWithSelf =
+            let
+              cacheFeatures = featuresByPackageId.${packageId} or [ ];
+              combinedFeatures = sortedUnique (cacheFeatures ++ enabledFeatures);
+            in
+            featuresByPackageId // {
+              "${packageId}" = combinedFeatures;
+            };
+          cacheWithDependencies =
+            resolveDependencies cacheWithSelf "dep"
+              (
+                crateConfig.dependencies or [ ]
+                ++ lib.optionals
+                  (runTests && packageId == rootPackageId)
+                  (crateConfig.devDependencies or [ ])
+              );
+          cacheWithAll =
+            resolveDependencies
+              cacheWithDependencies "build"
+              (crateConfig.buildDependencies or [ ]);
+        in
+        cacheWithAll;
+
+    /* Returns the enabled dependencies given the enabled features. */
+    filterEnabledDependencies = { dependencies, features, target }:
+      assert (builtins.isList dependencies);
+      assert (builtins.isList features);
+      assert (builtins.isAttrs target);
+
+      lib.filter
+        (
+          dep:
+          let
+            targetFunc = dep.target or (features: true);
+          in
+          targetFunc { inherit features target; }
+          && (
+            !(dep.optional or false)
+            || builtins.any (doesFeatureEnableDependency dep) features
+          )
+        )
+        dependencies;
+
+    /* Returns whether the given feature should enable the given dependency. */
+    doesFeatureEnableDependency = dependency: feature:
+      let
+        name = dependency.rename or dependency.name;
+        prefix = "${name}/";
+        len = builtins.stringLength prefix;
+        startsWithPrefix = builtins.substring 0 len feature == prefix;
+      in
+      feature == name || feature == "dep:" + name || startsWithPrefix;
+
+    /* Returns the expanded features for the given inputFeatures by applying the
+      rules in featureMap.
+
+      featureMap is an attribute set which maps feature names to lists of further
+      feature names to enable in case this feature is selected.
+    */
+    expandFeatures = featureMap: inputFeatures:
+      assert (builtins.isAttrs featureMap);
+      assert (builtins.isList inputFeatures);
+      let
+        expandFeaturesNoCycle = oldSeen: inputFeatures:
+          if inputFeatures != [ ]
+          then
+            let
+              # The feature we're currently expanding.
+              feature = builtins.head inputFeatures;
+              # All the features we've seen/expanded so far, including the one
+              # we're currently processing.
+              seen = oldSeen // { ${feature} = 1; };
+              # Expand the feature but be careful to not re-introduce a feature
+              # that we've already seen: this can easily cause a cycle, see issue
+              # #209.
+              enables = builtins.filter (f: !(seen ? "${f}")) (featureMap."${feature}" or [ ]);
+            in
+            [ feature ] ++ (expandFeaturesNoCycle seen (builtins.tail inputFeatures ++ enables))
+          # No more features left, nothing to expand to.
+          else [ ];
+        outFeatures = expandFeaturesNoCycle { } inputFeatures;
+      in
+      sortedUnique outFeatures;
+
+    /* This function adds optional dependencies as features if they are enabled
+      indirectly by dependency features. This function mimics Cargo's behavior
+      described in a note at:
+      https://doc.rust-lang.org/nightly/cargo/reference/features.html#dependency-features
+    */
+    enableFeatures = dependencies: features:
+      assert (builtins.isList features);
+      assert (builtins.isList dependencies);
+      let
+        additionalFeatures = lib.concatMap
+          (
+            dependency:
+              assert (builtins.isAttrs dependency);
+              let
+                enabled = builtins.any (doesFeatureEnableDependency dependency) features;
+              in
+              if (dependency.optional or false) && enabled
+              then [ (dependency.rename or dependency.name) ]
+              else [ ]
+          )
+          dependencies;
+      in
+      sortedUnique (features ++ additionalFeatures);
+
+    /*
+      Returns the actual features for the given dependency.
+
+      features: The features of the crate that refers this dependency.
+    */
+    dependencyFeatures = features: dependency:
+      assert (builtins.isList features);
+      assert (builtins.isAttrs dependency);
+      let
+        defaultOrNil =
+          if dependency.usesDefaultFeatures or true
+          then [ "default" ]
+          else [ ];
+        explicitFeatures = dependency.features or [ ];
+        additionalDependencyFeatures =
+          let
+            name = dependency.rename or dependency.name;
+            stripPrefixMatch = prefix: s:
+              if lib.hasPrefix prefix s
+              then lib.removePrefix prefix s
+              else null;
+            extractFeature = feature: lib.findFirst
+              (f: f != null)
+              null
+              (map (prefix: stripPrefixMatch prefix feature) [
+                (name + "/")
+                (name + "?/")
+              ]);
+            dependencyFeatures = lib.filter (f: f != null) (map extractFeature features);
+          in
+          dependencyFeatures;
+      in
+      defaultOrNil ++ explicitFeatures ++ additionalDependencyFeatures;
+
+    /* Sorts and removes duplicates from a list of strings. */
+    sortedUnique = features:
+      assert (builtins.isList features);
+      assert (builtins.all builtins.isString features);
+      let
+        outFeaturesSet = lib.foldl (set: feature: set // { "${feature}" = 1; }) { } features;
+        outFeaturesUnique = builtins.attrNames outFeaturesSet;
+      in
+      builtins.sort (a: b: a < b) outFeaturesUnique;
+
+    deprecationWarning = message: value:
+      if strictDeprecation
+      then builtins.throw "strictDeprecation enabled, aborting: ${message}"
+      else builtins.trace message value;
+
+    #
+    # crate2nix/default.nix (excerpt end)
+    #
+  };
+}
+
diff --git a/users/kranzes/wasm-hello-world/Cargo.toml b/users/kranzes/wasm-hello-world/Cargo.toml
new file mode 100644
index 000000000000..e08caa7ecf24
--- /dev/null
+++ b/users/kranzes/wasm-hello-world/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "wasm_hello_world"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+wasm-bindgen = "0.2.92"
diff --git a/users/kranzes/wasm-hello-world/default.nix b/users/kranzes/wasm-hello-world/default.nix
new file mode 100644
index 000000000000..0970f955deff
--- /dev/null
+++ b/users/kranzes/wasm-hello-world/default.nix
@@ -0,0 +1,15 @@
+{ pkgs, lib, ... }:
+
+(pkgs.pkgsCross.wasm32-unknown-none.callPackage ./Cargo.nix { }).rootCrate.build.overrideAttrs (oldAttrs: {
+  installPhase = ''
+    ${lib.getExe pkgs.wasm-bindgen-cli} \
+      --target web \
+      --out-dir $out \
+      --out-name ${oldAttrs.crateName} \
+      --no-typescript \
+      target/lib/${oldAttrs.crateName}-${oldAttrs.metadata}.wasm
+
+      mv src/*.html $out
+  '';
+})
+
diff --git a/users/kranzes/wasm-hello-world/src/index.html b/users/kranzes/wasm-hello-world/src/index.html
new file mode 100644
index 000000000000..d6366c8ee8b1
--- /dev/null
+++ b/users/kranzes/wasm-hello-world/src/index.html
@@ -0,0 +1,19 @@
+<html>
+  <head>
+    <meta content="text/html;charset=utf-8" http-equiv="Content-Type"/>
+  </head>
+  <body>
+    <script type="module">
+      import init, { hello_world } from './wasm_hello_world.js';
+
+      async function run() {
+        await init();
+
+	hello_world();
+      }
+
+      run();
+    </script>
+  </body>
+</html>
+
diff --git a/users/kranzes/wasm-hello-world/src/lib.rs b/users/kranzes/wasm-hello-world/src/lib.rs
new file mode 100644
index 000000000000..c184214822e7
--- /dev/null
+++ b/users/kranzes/wasm-hello-world/src/lib.rs
@@ -0,0 +1,11 @@
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+extern "C" {
+    fn alert(s: &str);
+}
+
+#[wasm_bindgen]
+pub fn hello_world() {
+    alert("Hello World!");
+}