Support ignoring generated files

src/api-client.ts

@@ -190,9 +190,7 @@ export async function getWorkflowRelativePath(): Promise<string> {
  * the GitHub API, but after that the result will be cached.
  */
 export async function getAnalysisKey(): Promise<string> {
-  const analysisKeyEnvVar = EnvVar.ANALYSIS_KEY;
-
-  let analysisKey = process.env[analysisKeyEnvVar];
+  let analysisKey = process.env[EnvVar.ANALYSIS_KEY];
   if (analysisKey !== undefined) {
     return analysisKey;
   }
@@ -201,7 +199,7 @@ export async function getAnalysisKey(): Promise<string> {
   const jobName = getRequiredEnvParam("GITHUB_JOB");
 
   analysisKey = `${workflowPath}:${jobName}`;
-  core.exportVariable(analysisKeyEnvVar, analysisKey);
+  core.exportVariable(EnvVar.ANALYSIS_KEY, analysisKey);
   return analysisKey;
 }
 

src/config-utils.ts

@@ -60,6 +60,7 @@ import {
   getCodeQLMemoryLimit,
   getErrorMessage,
   isInTestMode,
+  joinAtMost,
 } from "./util";
 
 export * from "./config/db-config";
@@ -958,17 +959,27 @@ export async function initConfig(
   // the `paths-ignore` configuration.
   if ((await features.getValue(Feature.IgnoreGeneratedFiles)) && isCCR()) {
     try {
+      const generatedFilesCheckStartedAt = performance.now();
       const generatedFiles = await getGeneratedFiles(inputs.sourceRoot);
+      const generatedFilesDuration = Math.round(
+        performance.now() - generatedFilesCheckStartedAt,
+      );
 
       if (generatedFiles.length > 0) {
         config.computedConfig["paths-ignore"] ??= [];
         config.computedConfig["paths-ignore"].push(...generatedFiles);
         logger.info(
-          `Detected ${generatedFiles.length} generated file(s), which will be excluded from analysis: ${generatedFiles.join(", ")}`,
+          `Detected ${generatedFiles.length} generated file(s), which will be excluded from analysis: ${joinAtMost(generatedFiles, ", ", 10)}`,
         );
       } else {
         logger.info(`Found no generated files.`);
       }
+
+      await logGeneratedFilesTelemetry(
+        config,
+        generatedFilesDuration,
+        generatedFiles.length,
+      );
     } catch (error) {
       logger.info(`Cannot ignore generated files: ${getErrorMessage(error)}`);
     }
@@ -1413,3 +1424,32 @@ async function logGitVersionTelemetry(
     );
   }
 }
+
+/**
+ * Logs the time it took to identify generated files and how many were discovered as
+ * a telemetry diagnostic.
+ * */
+async function logGeneratedFilesTelemetry(
+  config: Config,
+  duration: number,
+  generatedFilesCount: number,
+): Promise<void> {
+  if (config.languages.length < 1) {
+    return;
+  }
+
+  addDiagnostic(
+    config,
+    // Arbitrarily choose the first language. We could also choose all languages, but that
+    // increases the risk of misinterpreting the data.
+    config.languages[0],
+    makeTelemetryDiagnostic(
+      "codeql-action/generated-files-telemetry",
+      "Generated files telemetry",
+      {
+        duration,
+        generatedFilesCount,
+      },
+    ),
+  );
+}

src/git-utils.test.ts

@@ -439,7 +439,7 @@ test("GitVersionInfo.isAtLeast correctly compares versions", async (t) => {
 test("listFiles returns array of file paths", async (t) => {
   sinon
     .stub(gitUtils, "runGitCommand")
-    .resolves(["dir/file.txt", "README.txt"].join(os.EOL));
+    .resolves(["dir/file.txt", "README.txt", ""].join(os.EOL));
 
   await t.notThrowsAsync(async () => {
     const result = await gitUtils.listFiles("/some/path");
@@ -453,14 +453,15 @@ test("getGeneratedFiles returns generated files only", async (t) => {
 
   runGitCommandStub
     .onFirstCall()
-    .resolves(["dir/file.txt", "test.json", "README.txt"].join(os.EOL));
+    .resolves(["dir/file.txt", "test.json", "README.txt", ""].join(os.EOL));
   runGitCommandStub
     .onSecondCall()
     .resolves(
       [
         "dir/file.txt: linguist-generated: unspecified",
         "test.json: linguist-generated: true",
         "README.txt: linguist-generated: false",
+        "",
       ].join(os.EOL),
     );
 

src/git-utils.ts

@@ -411,7 +411,7 @@ export async function listFiles(workingDirectory: string): Promise<string[]> {
     ["ls-files"],
     "Unable to list tracked files.",
   );
-  return stdout.split(os.EOL);
+  return stdout.split(os.EOL).filter((line) => line.trim().length > 0);
 }
 
 /**
@@ -434,8 +434,8 @@ export async function getGeneratedFiles(
   const regex = /^([^:]+): linguist-generated: true$/;
   for (const result of stdout.split(os.EOL)) {
     const match = result.match(regex);
-    if (match) {
-      generatedFiles.push(match[1]);
+    if (match && match[1].trim().length > 0) {
+      generatedFiles.push(match[1].trim());
     }
   }