[compiler][snap] Fix for filter mode with nested files, 'error.' prefix

Fixes some issues i ran into w my recent snap changes:
* Correctly match against patterns that contain subdirectories, eg `fbt/fbt-call`
* When checking if the input pattern has an extension, only prune known supported extensions. Our convention of `error.<name>` for fixtures that error makes the rest of the test name look like an extension to `path.extname()`.

Tested with lots of different patterns including `error.` examples at the top level and in nested directories, etc.

compiler/packages/snap/src/fixture-utils.ts

@@ -44,21 +44,6 @@ function stripExtension(filename: string, extensions: Array<string>): string {
   return filename;
 }
 
-/**
- * Strip all extensions from a filename
- * e.g., "foo.expect.md" -> "foo"
- */
-function stripAllExtensions(filename: string): string {
-  let result = filename;
-  while (true) {
-    const extension = path.extname(result);
-    if (extension === '') {
-      return result;
-    }
-    result = path.basename(result, extension);
-  }
-}
-
 export async function readTestFilter(): Promise<TestFilter | null> {
   if (!(await exists(FILTER_PATH))) {
     throw new Error(`testfilter file not found at \`${FILTER_PATH}\``);
@@ -134,13 +119,15 @@ async function readInputFixtures(
           // `alias-while` => search for `alias-while{.js,.jsx,.ts,.tsx}`
           // `alias-while.js` => search as-is
           // `alias-while.expect.md` => search for `alias-while{.js,.jsx,.ts,.tsx}`
-          const basename = path.basename(pattern);
-          const basenameWithoutExt = stripAllExtensions(basename);
-          const hasExtension = basename !== basenameWithoutExt;
+          const patternWithoutExt = stripExtension(pattern, [
+            ...INPUT_EXTENSIONS,
+            SNAPSHOT_EXTENSION,
+          ]);
+          const hasExtension = pattern !== patternWithoutExt;
           const globPattern =
             hasExtension && !pattern.endsWith(SNAPSHOT_EXTENSION)
               ? pattern
-              : `${basenameWithoutExt}{${INPUT_EXTENSIONS.join(',')}}`;
+              : `${patternWithoutExt}{${INPUT_EXTENSIONS.join(',')}}`;
           return glob.glob(globPattern, {
             cwd: rootDir,
           });
@@ -181,7 +168,10 @@ async function readOutputFixtures(
       await Promise.all(
         filter.paths.map(pattern => {
           // Strip all extensions and find matching .expect.md files
-          const basenameWithoutExt = stripAllExtensions(pattern);
+          const basenameWithoutExt = stripExtension(pattern, [
+            ...INPUT_EXTENSIONS,
+            SNAPSHOT_EXTENSION,
+          ]);
           return glob.glob(`${basenameWithoutExt}${SNAPSHOT_EXTENSION}`, {
             cwd: rootDir,
           });