feat(nix/writeTree): init r/7589

Add //nix/writeTree, a function to make a derivation to build a
directory structure from a Nix attribute set.

Co-authored-by: sterni <sternenseemann@systemli.org>
Change-Id: I9c0fc91611a55a20ad33de6f2b27abde4b6abd21
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10963
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
Autosubmit: aspen <root@gws.fyi>
Reviewed-by: aspen <root@gws.fyi>

1 files changed, 93 insertions, 0 deletions

diff --git a/nix/writeTree/tests/default.nix b/nix/writeTree/tests/default.nix
new file mode 100644
index 000000000000..c5858ee96eb8
--- /dev/null
+++ b/nix/writeTree/tests/default.nix
@@ -0,0 +1,93 @@
+{ depot, pkgs, lib, ... }:
+
+let
+  inherit (pkgs) runCommand writeText writeTextFile;
+  inherit (depot.nix) writeTree;
+
+  checkTree = name: tree: expected:
+    runCommand "writeTree-test-${name}"
+      {
+        nativeBuildInputs = [ pkgs.buildPackages.lr ];
+        passAsFile = [ "expected" ];
+        inherit expected;
+      } ''
+      actualPath="$NIX_BUILD_TOP/actual"
+      cd ${lib.escapeShellArg (writeTree name tree)}
+      lr . > "$actualPath"
+      diff -u "$expectedPath" "$actualPath" | tee "$out"
+    '';
+in
+
+depot.nix.readTree.drvTargets {
+  empty = checkTree "empty" { }
+    ''
+      .
+    '';
+
+  simple-paths = checkTree "simple"
+    {
+      writeTree = {
+        meta = {
+          "owners.txt" = ../OWNERS;
+        };
+        "code.nix" = ../default.nix;
+        all-tests = ./.;
+        nested.dirs.eval-time = builtins.toFile "owothia" ''
+          hold me owo
+        '';
+      };
+    }
+    ''
+      .
+      ./writeTree
+      ./writeTree/all-tests
+      ./writeTree/all-tests/default.nix
+      ./writeTree/code.nix
+      ./writeTree/meta
+      ./writeTree/meta/owners.txt
+      ./writeTree/nested
+      ./writeTree/nested/dirs
+      ./writeTree/nested/dirs/eval-time
+    '';
+
+  empty-dirs = checkTree "empty-dirs"
+    {
+      this.dir.is.empty = { };
+      so.is.this.one = { };
+    }
+    ''
+      .
+      ./so
+      ./so/is
+      ./so/is/this
+      ./so/is/this/one
+      ./this
+      ./this/dir
+      ./this/dir/is
+      ./this/dir/is/empty
+    '';
+
+  drvs = checkTree "drvs"
+    {
+      file-drv = writeText "road.txt" ''
+        Any road followed precisely to its end leads precisely nowhere.
+      '';
+      dir-drv = writeTextFile {
+        name = "dir-of-text";
+        destination = "/text/in/more/dirs.txt";
+        text = ''
+          Climb the mountain just a little bit to test that it’s a mountain.
+          From the top of the mountain, you cannot see the mountain.
+        '';
+      };
+    }
+    ''
+      .
+      ./dir-drv
+      ./dir-drv/text
+      ./dir-drv/text/in
+      ./dir-drv/text/in/more
+      ./dir-drv/text/in/more/dirs.txt
+      ./file-drv
+    '';
+}