Commit build script

build.mjs

@@ -0,0 +1,139 @@
+/* Horrifying fixer-upper for ESM imports */
+import * as fs from "fs";
+import {existsSync, promises as fsp} from "fs";
+import * as path from "path";
+
+const DIST = path.join(process.cwd(), "dist");
+const NODE_MODULES = path.join(process.cwd(), "node_modules");
+
+build();
+
+async function build() {
+  for (const type of ["esm", "cjs"]) {
+    const dir = path.join(DIST, type);
+    const extn = type === "esm" ? "mjs" : "cjs";
+
+    // rename files first
+    await walkDir(dir, async filename => {
+      if (!filename.endsWith(".js"))
+        return;
+      await renameExtension(filename, extn);
+    });
+
+
+    // now fix imports
+    await walkDir(dir, async filename => {
+      if (!filename.endsWith(`.${extn}`))
+        return;
+      await fixImports(filename, type);
+    });
+  }
+}
+
+/**
+ * Recursively walk a directory
+ * @param {string} dirname Name of directory to walk
+ * @param {(filename: string) => Promise<void>} callback Callback
+ */
+async function walkDir(dirname, callback) {
+  const files = (await fsp.readdir(dirname)).map(filename => path.join(dirname, filename));
+
+  /* first rename all files */
+
+  await Promise.all(files.map(async filename => {
+    const stat = await fsp.stat(filename);
+    if (stat.isDirectory()) {
+      return walkDir(filename, callback);
+    }
+    await callback(filename);
+  }));
+}
+
+/**
+ * Add extensions to relative imports
+ * @param {string} filename File to operate on.
+ * @param {"esm" | "cjs"} type Javascript module system in use.
+ */
+async function fixImports(filename, type = "esm") {
+  let content = await fsp.readFile(filename, "utf8");
+  const regex = (type === "esm" ?
+    /^((?:ex|im)port .+? from\s+)(["'])(.+?)(\2;?)$/gm :
+    /(require\()(['"])(.+?)(\2\))/gm
+  );
+  content = content.replaceAll(regex, (match, head, q, name, tail) => {
+    // already has extension
+    if (name.match(/\.[cm]?js$/)) {
+      return match;
+    }
+
+    // relative imports
+    if (name.startsWith(".")) {
+      // figure out which file it's referring to
+      const target = findExtension(path.dirname(filename), name);
+      return (head + q + target + tail);
+    } else {
+    }
+    return match;
+  });
+
+  await fsp.writeFile(filename, content);
+}
+
+/**
+ * Find extension
+ */
+function findExtension(pathname, relative) {
+  const filename = path.resolve(pathname, relative);
+  for (const extn of ["mjs", "js", "cjs"]) {
+    let full = filename + "." + extn;
+
+    if (!existsSync(full) && existsSync(filename + "/index." + extn)) {
+      full = filename + "/index." + extn;
+    }
+
+    if (existsSync(full)) {
+      let rewrite = path.relative(pathname, full);
+      if (!rewrite.startsWith(".")) {
+        rewrite = "./" + rewrite;
+      }
+      return rewrite;
+    }
+  }
+  throw new Error(`Could not resolve ${filename}`);
+}
+
+/**
+ * Find package.json
+ * @param {string} name Name of package.
+ */
+function findPackageJson(name) {
+  const packageName = getPackageName(name);
+  let dirname = NODE_MODULES;
+  while (true) {
+    const filename = path.join(dirname, packageName, "package.json");
+    if (fs.existsSync(filename))
+      return filename;
+    dirname = path.normalize(path.join(dirname, ".."));
+    if (dirname === "/")
+      throw new Error(`Could not find package.json for ${name}`);
+  }
+}
+
+/**
+ * Get name of NPM package
+ * @param {string} name Import string to resolve.
+ */
+function getPackageName(name) {
+  const parts = name.split("/");
+  if (name.startsWith("@")) {
+    return parts.slice(0, 2).join("/");
+  }
+  return parts[0];
+}
+
+/**
+ * Change file extension
+ */
+async function renameExtension(filename, extn = "mjs") {
+  await fsp.rename(filename, filename.replace(/\.js$/, `.${extn}`));
+}