Move type:module declaration into package.json. (#4355)

* Rename `switch_package_to_release.js` to `.cjs`

Slightly surprisingly, the symlink is enough to make `node
switch_package_to_release.js` work.

* Rename .eslintrc.js to .cjs

Again, declare this as commonjs

* Move `type:module` declaration into package.json.

matrix-js-sdk is built into ECMAScript modules, and we should declare it as
such. See https://nodejs.org/api/packages.html#type. Failure to do so causes
problems for javascript projects attempting to build against matrix-js-sdk: see #4347.

Previously, we did this as part of the package.json switcheroo, but that is
unnecessarily fragile.

matrix-react-sdk, element-web, etc are unaffected by this, because they use the
typescript files directly, by importing `matrix-js-sdk/src/...`.

package.json

@@ -31,8 +31,9 @@
     "keywords": [
         "matrix-org"
     ],
-    "main": "./lib/index.js",
-    "browser": "./lib/browser-index.js",
+    "type": "module",
+    "main": "./src/index.js",
+    "browser": "./src/browser-index.js",
     "matrix_src_main": "./src/index.ts",
     "matrix_src_browser": "./src/browser-index.ts",
     "matrix_lib_main": "./lib/index.js",

scripts/release/pre-release.sh

@@ -12,6 +12,3 @@ do
         jq ".$i = .matrix_lib_$i" package.json > package.json.new && mv package.json.new package.json && yarn prettier --write package.json
     fi
 done
-
-# Ensure that "type": "module" is present
-jq '.type = "module"' package.json > package.json.new && mv package.json.new package.json && yarn prettier --write package.json

scripts/switch_package_to_release.cjs

@@ -0,0 +1,18 @@
+#!/usr/bin/env node
+
+const fsProm = require("fs/promises");
+
+const PKGJSON = "package.json";
+
+async function main() {
+    const pkgJson = JSON.parse(await fsProm.readFile(PKGJSON, "utf8"));
+    for (const field of ["main", "typings"]) {
+        if (pkgJson["matrix_lib_" + field] !== undefined) {
+            pkgJson[field] = pkgJson["matrix_lib_" + field];
+        }
+    }
+
+    await fsProm.writeFile(PKGJSON, JSON.stringify(pkgJson, null, 2));
+}
+
+main();

scripts/switch_package_to_release.js

@@ -0,0 +1 @@
+switch_package_to_release.cjs