Initial commit; basic functionality works

package.json

@@ -0,0 +1,11 @@
+{
+  "name": "haskell-loader",
+  "version": "0.1.0",
+  "description": "Webpack loader for Haskell",
+  "main": "src/index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "",
+  "license": "BSD-3-Clause"
+}

src/index.js

@@ -0,0 +1,110 @@
+const child_process = require('node:child_process');
+const path = require('path');
+const readFileSync = require('fs').readFileSync;
+
+module.exports = function(source) {
+  const options = this.getOptions();
+  const callback = this.async();
+  const cabalFilePath = path.resolve(this.resourcePath);
+  const cabalFileDir = path.dirname(cabalFilePath);
+
+
+  let result;
+  try {
+    //TODO: re-enable jsaddle loading
+    if (false && options.dev) {
+      if (options.isServer) {
+        // no-op
+        result = 'export function haskellEngine(arg, global) { };';
+      } else { // !options.isServer
+        this.cacheable(false);
+        const command = 'ghcid -r -W -c"cabal repl ' + path.basename(cabalFilePath) + '"';
+        const ghcid_process = child_process.spawn(
+          'nix-shell',
+          ['-A', 'shells.ghc', '--run', command],
+          {
+            cwd: cabalFileDir,
+            stdio: 'inherit',
+          }
+        );
+        // ghcid_process should not stop
+        ghcid_process.on('close', (code) => {
+          throw("ghcid process stopped");
+        });
+        // TODO: we should ideally wait for the ghcid to successfully start the jsaddle server
+
+        //TODO: xhr.onerror
+        result =
+          'import * as react from "react";' +
+          'console.log("retrieving jsaddle.js");' +
+          'const jsaddleRoot = "http://localhost:3001";' +
+          'const xhr = new XMLHttpRequest();' +
+          'xhr.open("GET", jsaddleRoot + "/jsaddle.js");' +
+          'var result;' +
+          'xhr.onload = () => {' +
+          '  eval("(function(JSADDLE_ROOT, arg, global) {" + xhr.response + "})")(jsaddleRoot, { react, setVal: (v) => { result = v; } }, window);' +
+          '};' +
+          'xhr.send();';
+      }
+    } else {  // !options.dev
+      if(options.isServer) {
+        // no-op
+        result = '';
+      } else {
+        //TODO: Correctly report dependencies
+        const build_command = 'js-unknown-ghcjs-cabal build ' + path.basename(cabalFilePath);
+        const build_result = child_process.spawnSync(
+          'nix-shell',
+          ['-A', 'shells.ghcjs', '--run', build_command],
+          {
+            cwd: cabalFileDir,
+            stdio: 'inherit',
+          }
+        );
+        if (build_result.error != null) {
+          throw(build_result.error);
+        }
+
+        // If the cabal build has no changes to build, it only prints "Up to date"
+        // In order to get the output dir we currently have only the cabal run command
+        // The cabal list-bins command is present in cabal v3.4
+        const run_command = 'js-unknown-ghcjs-cabal run ' + path.basename(cabalFilePath) + ' || true';
+        const run_result = child_process.spawnSync(
+          'nix-shell',
+          ['-A', 'shells.ghcjs', '--run', run_command],
+          {
+            cwd: cabalFileDir,
+            stdio: 'pipe',
+            encoding: 'utf8',
+          }
+        );
+        if (run_result.error != null) {
+          throw(run_result.error);
+        }
+
+        // The output of cabal run prints this in the end of stderr
+        // <dir>: createProcess: posix_spawnp: does not exist (No such file or directory)
+        // We need to get the <dir> from this line
+        // The end of strerr has '\n', so second last item
+        const last_line = run_result.stderr.split('\n').at(-2);
+        const out_dir = last_line.split(': createProcess:')[0] + '.jsexe';
+
+        const allJs = readFileSync(out_dir + '/all.js');
+
+        var numReplacements = 0;
+        // Make main start in sync mode.  This way, our components will be available as soon as the js-side `import` function finishes.
+        const syncMainJs = allJs.toString().replace(/\nh\$main(.*);\n/, (_, closureName) => { numReplacements++; return '\nh$runSync(' + closureName + ', false);\nh$startMainLoop();\n'; });
+        if(numReplacements !== 1) {
+          throw Error('Expected to find one h$main invocation in all.js, but found ' + numReplacements.toString());
+        }
+
+        result = "import * as react from 'react'; function haskellEngine(arg, global) { function getProgramArg() { return arg; };" + syncMainJs + "}; var result; haskellEngine({ react, setVal: (v) => { result = v; } }, window); export default result;";
+      }
+    }
+  } catch (error) {
+    callback(error);
+    return;
+  }
+
+  callback(null, result);
+}