Re-throw errors from PostCSS nodes

[thecrypticace]

Fixes #18370

[thecrypticace]

As far as I can tell from the original reproduction in #17295 this still doesn't help.

From this comment angular/angular-cli#29789 (comment)

This issue was related to us not throwing a PostCSS error but even if we do that it doesn't work.

This will take some more investigation.

[meet4171]

nice work

[thecrypticace]

I found the Angular bug.

Leaving me a note with the reduced CSS plugin so I can file a bug report:

/*
 * Commentary:
 * This plugin demonstrates a rebuild bug in Angular 19
 *
 * The setup consists of three files:
 *
 * File 1: styles.css:
 * ```css
 * @import "./imported.css";
 * ```
 *
 * File 2: imported.css:
 * ```css
 * @--throw-me;
 * ```
 *
 * File 3: This plugin
 *
 * Reproduction:
 *
 * # Build
 * - `npm run start`
 *
 * # Cause an error
 * - `gsed -i 's/@--throw-me/@throw-me/' src/imported.css`
 *
 * # Revert the error and see it's still broken
 * - `gsed -i 's/@throw-me/@--throw-me/' src/imported.css`
 *
 * # Try editing it again and see that it doesn't rebuild
 * - `gsed -i 's/@--throw-me/@--throw-me-2/' src/imported.css`
 *
 * # To recover you *must* edit the "root" stylesheet
 *
 * - `echo '\n.test{}' > src/styles.css`
 */

module.exports = function tailwindcss() {
  return {
    postcssPlugin: "tailwindcss",
    async Once(root, { result }) {
      console.log("postcss called for", result.opts.from);

      // Precondition:
      //
      // We only care about compiles to `styles.css` for this bug report
      if (!result.opts.from?.endsWith("styles.css")) return;

      // Note:
      //
      // Removing the `@import` prevents this plugin from being called for
      // `imported.css` too. This does not affect reproduction of the bug.
      root.removeAll();

      // Requirement 1:
      //
      // `styles.css` must emit a dependency on a file that it also `@import`s
      // during a successful build.
      let path = require("path");
      let importedPath = path.resolve(path.dirname(result.opts.from), "./imported.css");
      result.messages.push({
        type: "dependency",
        plugin: "my-plugin",
        parent: result.opts.from,
        file: importedPath,
      });

      // Requirement 2:
      //
      // `styles.css` must throw an error after a successful rebuild due to
      // a change in an `@import`-ed stylesheet.
      //
      // We'll do this by checking the content directly as we're not using
      // `postcss-import` or anything like that here.
      //
      // Trigger the error by changing `@--throw-me` to `@throw-me`.
      let fs = require("fs");
      let importedFile = fs.readFileSync(importedPath, "utf-8");
      if (importedFile.includes("@throw-me")) throw root.error("ohno");
    },
  };
};

module.exports.postcss = true;

[RobinMalfait]

Looking good, but I think this small API would make it even better.