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authorsterni <sternenseemann@systemli.org>2021-08-25T00·45+0200
committersterni <sternenseemann@systemli.org>2021-08-26T15·34+0000
commit9ed439bfbddee7915c4011f8a6ba7562b3375ac8 (patch)
tree6343c44bb40676d684aceec57bab7b26388f7914 /users/sterni/nix/html/default.nix
parent17d78867bbef8a3df1271137a2db18b3584cdc39 (diff)
feat(users/sterni/nix): cursed nix html DSL r/2784
Couldn't sleep, so I made a surprisingly neat way to render HTML
documents in Nix using our favorite feature __findFile:

  let
    inherit (depot.users.sterni.nix.html) __findFile esc;

  in

  <html> {} [
    (<head> {} [
      (<meta> { charset = "utf-8"; } null)
      (<title> {} (esc "hello"))
    ])
    (<body> {} [
      (<h1> {} (esc "hello world"))
    ])
  ]

=> "<html><head><meta charset=\"utf-8\"/><title>hello</title></head><body><h1>hello world</h1></body></html>"

Change-Id: Id36808a56ae3da3b5263c06f29342fc22d105c21
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3410
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Diffstat (limited to 'users/sterni/nix/html/default.nix')
-rw-r--r--users/sterni/nix/html/default.nix119
1 files changed, 119 insertions, 0 deletions
diff --git a/users/sterni/nix/html/default.nix b/users/sterni/nix/html/default.nix
new file mode 100644
index 000000000000..2498d832aadf
--- /dev/null
+++ b/users/sterni/nix/html/default.nix
@@ -0,0 +1,119 @@
+# Copyright © 2021 sterni
+# SPDX-License-Identifier: MIT
+#
+# This file provides a cursed HTML DSL for nix which works by overloading
+# the NIX_PATH lookup operation via angle bracket operations, e. g. `<nixpkgs>`.
+
+{ ... }:
+
+let
+  /* Escape everything we have to escape in an HTML document if either
+     in a normal context or an attribute string (`<>&"'`).
+
+     A shorthand for this function called `esc` is also provided.
+
+     Type: string -> string
+
+     Example:
+
+     escapeMinimal "<hello>"
+     => "&lt;hello&gt;"
+  */
+  escapeMinimal = builtins.replaceStrings
+    [ "<"    ">"    "&"     "\""     "'"      ]
+    [ "&lt;" "&gt;" "&amp;" "&quot;" "&#039;" ];
+
+  /* Return a string with a correctly rendered tag of the given name,
+     with the given attributes which are automatically escaped.
+
+     If the content argument is `null`, the tag will have no children nor a
+     closing element. If the content argument is a string it is used as the
+     content as is (unescaped). If the content argument is a list, its
+     elements are concatenated.
+
+     `renderTag` is only an internal function which is reexposed as `__findFile`
+     to allow for much neater syntax than calling `renderTag` everywhere:
+
+     ```nix
+     { depot, ... }:
+     let
+       inherit (depot.users.sterni.nix.html) __findFile esc;
+     in
+
+     <html> {} [
+       (<head> {} (<title> {} (esc "hello world")))
+       (<body> {} [
+         (<h1> {} (esc "hello world"))
+         (<p> {} (esc "foo bar"))
+       ])
+     ]
+
+     ```
+
+     As you can see, the need to call a function disappears, instead the
+     `NIX_PATH` lookup operation via `<foo>` is overloaded, so it becomes
+     `renderTag "foo"` automatically.
+
+     Since the content argument may contain the result of other `renderTag`
+     calls, we can't escape it automatically. Instead this must be done manually
+     using `esc`.
+
+     Type: string -> attrs<string> -> (list<string> | string | null) -> string
+
+     Example:
+
+     <link> {
+       rel = "stylesheet";
+       href = "/css/main.css";
+       type = "text/css";
+     } null
+
+     renderTag "link" {
+       rel = "stylesheet";
+       href = "/css/main.css";
+       type = "text/css";
+     } null
+
+     => "<link href=\"/css/main.css\" rel=\"stylesheet\" type=\"text/css\"/>"
+
+     <p> {} [
+       "foo "
+       (<strong> {} "bar")
+     ]
+
+     renderTag "p" {} "foo <strong>bar</strong>"
+     => "<p>foo <strong>bar</strong></p>"
+  */
+  renderTag = tag: attrs: content:
+    let
+      attrs' = builtins.concatStringsSep "" (
+        builtins.map (n:
+          " ${escapeMinimal n}=\"${escapeMinimal (toString attrs.${n})}\""
+        ) (builtins.attrNames attrs)
+      );
+      content' =
+        if builtins.isList content
+        then builtins.concatStringsSep "" content
+        else content;
+    in
+      if content == null
+      then "<${tag}${attrs'}/>"
+      else "<${tag}${attrs'}>${content'}</${tag}>";
+
+  /* Prepend "<!DOCTYPE html>" to a string.
+
+     Type: string -> string
+
+     Example:
+
+     withDoctype (<body> {} (esc "hello"))
+     => "<!DOCTYPE html><body>hello</body>"
+  */
+  withDoctype = doc: "<!DOCTYPE html>" + doc;
+
+in {
+  inherit escapeMinimal renderTag withDoctype;
+
+  __findFile = _: renderTag;
+  esc = escapeMinimal;
+}