Improve errors & warnings in autobuild

Author: Max Veytsman

lib/autobuild.js

@@ -15,7 +15,8 @@ async function run() {
     // We want pick the dominant language in the repo from the ones we're able to build
     // The languages are sorted in order specified by user or by lines of code if we got
     // them from the GitHub API, so try to build the first language on the list.
-    const language = process.env[sharedEnv.CODEQL_ACTION_TRACED_LANGUAGES]?.split(',')[0];
+    const autobuildLanguages = process.env[sharedEnv.CODEQL_ACTION_TRACED_LANGUAGES]?.split(',') || [];
+    const language = autobuildLanguages[0];
 
     if (!language) {
       core.info("None of the languages in this project require extra build steps");
@@ -24,6 +25,10 @@ async function run() {
 
     core.debug(`Detected dominant traced language: ${language}`);
 
+    if (autobuildLanguages.length > 1) {
+      core.warning(`We will only automatically build ${language} code. If you wish to scan ${autobuildLanguages.slice(1).join(' and ')}, you must replace this block with custom build steps.`);
+    }
+
     core.startGroup(`Attempting to automatically build ${language} code`);
     // TODO: share config accross actions better via env variables
     const codeqlCmd = util.getRequiredEnvParam(sharedEnv.CODEQL_ACTION_CMD);
@@ -53,6 +58,6 @@ async function run() {
 }
 
 run().catch(e => {
-  core.setFailed("autobuild action failed: " + e);
+  core.setFailed("We were unable to automatically build your code. Please replace the call to the autobuild action with your custom build steps. codeql/autobuild action failed.  " + e);
   console.log(e);
 });