Infer compression method from URL

Using the downloaded path is unreliable since we may have removed the file extension.

src/setup-codeql.ts

@@ -507,6 +507,7 @@ export const downloadCodeQL = async function (
     `Downloading CodeQL tools from ${codeqlURL} . This may take a while.`,
   );
 
+  const compressionMethod = tar.inferCompressionMethod(codeqlURL);
   const dest = path.join(tempDir, uuidV4());
   const finalHeaders = Object.assign(
     { "User-Agent": "CodeQL Action" },
@@ -528,8 +529,10 @@ export const downloadCodeQL = async function (
 
   logger.debug("Extracting CodeQL bundle.");
   const extractionStart = performance.now();
-  const { compressionMethod, outputPath: extractedBundlePath } =
-    await tar.extract(archivedBundlePath);
+  const extractedBundlePath = await tar.extract(
+    archivedBundlePath,
+    compressionMethod,
+  );
   const extractionDurationMs = Math.round(performance.now() - extractionStart);
   logger.debug(
     `Finished extracting CodeQL bundle to ${extractedBundlePath} (${extractionDurationMs} ms).`,
@@ -658,8 +661,10 @@ export async function setupCodeQLBundle(
   let toolsSource: ToolsSource;
   switch (source.sourceType) {
     case "local": {
-      const { outputPath } = await tar.extract(source.codeqlTarPath);
-      codeqlFolder = outputPath;
+      const compressionMethod = tar.inferCompressionMethod(
+        source.codeqlTarPath,
+      );
+      codeqlFolder = await tar.extract(source.codeqlTarPath, compressionMethod);
       toolsSource = ToolsSource.Local;
       break;
     }

src/tar.ts

@@ -78,23 +78,26 @@ export async function isZstdAvailable(
 
 export type CompressionMethod = "gzip" | "zstd";
 
-export async function extract(path: string): Promise<{
-  compressionMethod: CompressionMethod;
-  outputPath: string;
-}> {
-  if (path.endsWith(".tar.gz")) {
-    return {
-      compressionMethod: "gzip",
+export async function extract(
+  path: string,
+  compressionMethod: CompressionMethod,
+): Promise<string> {
+  switch (compressionMethod) {
+    case "gzip":
       // While we could also ask tar to autodetect the compression method,
       // we defensively keep the gzip call identical as requesting a gzipped
       // bundle will soon be a fallback option.
-      outputPath: await toolcache.extractTar(path),
-    };
+      return await toolcache.extractTar(path);
+    case "zstd":
+      // By specifying only the "x" flag, we ask tar to autodetect the
+      // compression method.
+      return await toolcache.extractTar(path, undefined, "x");
   }
-  return {
-    compressionMethod: "zstd",
-    // By specifying only the "x" flag, we ask tar to autodetect the compression
-    // method.
-    outputPath: await toolcache.extractTar(path, undefined, "x"),
-  };
+}
+
+export function inferCompressionMethod(path: string): CompressionMethod {
+  if (path.endsWith(".tar.gz")) {
+    return "gzip";
+  }
+  return "zstd";
 }