fix: handling of css module imports

lib/sass/source-to-class-names.ts

@@ -1,6 +1,48 @@
+import * as proxy from "identity-obj-proxy";
 import postcss from "postcss";
 import PostcssModulesPlugin from "postcss-modules";
 
+/**
+ * Use identity-obj-proxy for any imported CSS modules. This is to ignore any
+ * css module imports via `composes: ` or `@value` statements as the rules to propoerly
+ * resolve these requests may be totally arbitrary and different accross projects. Additionally,
+ * this is a simple way to avoid needing to write a sass loader for this tool. (To handle import of
+ * css modules written in SASS).
+ *
+ * The identity-obj-proxy is a simple object that returns the requested key as the value.
+ *
+ * So files with the following request
+ *
+ * ```css
+ * .foo {
+ *   composes: bar from "./baz.css";
+ * }
+ * ```
+ *
+ * will generate something like
+ *
+ * ```js
+ * {
+ *   foo: "foo-HASH123 bar", // the `bar` class is not resolved, and stubbed by the proxy
+ * }
+ * ```
+ *
+ * This should not affect the final types for a given file, since the types are
+ * generated only using the classes defined in the current file and not its imports.
+ *
+ * This has the added benefit of reducing system calls and disk access,
+ * so may perform faster in large projects in comparison to properly resolving these requests.
+ *
+ * The only drawback is that this does not process the import tree
+ * the way in which it is intended to be used, so broken imports
+ * will not be surfaced by this tool.
+ */
+class IdentityObjProxyLoader {
+  async fetch() {
+    return proxy;
+  }
+}
+
 /**
  * Converts a CSS source string to a list of exports (class names, keyframes, etc.)
  */
@@ -11,6 +53,7 @@ export const sourceToClassNames = async (
   let result: Record<string, string> = {};
   await postcss([
     PostcssModulesPlugin({
+      Loader: IdentityObjProxyLoader,
       getJSON: (_, json) => {
         result = json;
       },

package.json

@@ -54,6 +54,7 @@
     "@types/reserved-words": "^0.1.0",
     "@types/sass": "^1.16.0",
     "@types/yargs": "^17.0.8",
+    "@types/identity-obj-proxy": "^3.0.2",
     "@typescript-eslint/eslint-plugin": "^6.3.0",
     "@typescript-eslint/parser": "^6.3.0",
     "babel-jest": "^29.6.2",
@@ -87,6 +88,7 @@
     }
   },
   "dependencies": {
+    "identity-obj-proxy": "^3.0.0",
     "bundle-require": "^3.0.4",
     "chalk": "4.1.2",
     "change-case": "^4.1.2",