Improve detection of Rust in languages input

src/config-utils.ts

@@ -398,6 +398,15 @@ export async function getLanguages(
   return languages;
 }
 
+export function getRawLanguagesNoAutodetect(
+  languagesInput: string | undefined,
+): string[] {
+  return (languagesInput || "")
+    .split(",")
+    .map((x) => x.trim().toLowerCase())
+    .filter((x) => x.length > 0);
+}
+
 /**
  * Gets the set of languages in the current repository without checking to
  * see if these languages are actually supported by CodeQL.
@@ -416,12 +425,8 @@ export async function getRawLanguages(
   rawLanguages: string[];
   autodetected: boolean;
 }> {
-  // Obtain from action input 'languages' if set
-  const languagesFromInput = (languagesInput || "")
-    .split(",")
-    .map((x) => x.trim().toLowerCase())
-    .filter((x) => x.length > 0);
   // If the user has specified languages, use those.
+  const languagesFromInput = getRawLanguagesNoAutodetect(languagesInput);
   if (languagesFromInput.length) {
     return { rawLanguages: languagesFromInput, autodetected: false };
   }

src/init-action.ts

@@ -362,8 +362,16 @@ async function run() {
     }
     core.endGroup();
 
-    // Set CODEQL_ENABLE_EXPERIMENTAL_FEATURES for rust
-    if (getOptionalInput("languages")?.includes(KnownLanguage.rust)) {
+    // Set CODEQL_ENABLE_EXPERIMENTAL_FEATURES for Rust. We need to set this environment
+    // variable before initializing the config, otherwise Rust analysis will not be
+    // enabled.
+    if (
+      // Only enable Rust analysis if the user has explicitly requested it - don't
+      // enable it via language autodetection.
+      configUtils
+        .getRawLanguagesNoAutodetect(getOptionalInput("languages"))
+        .includes(KnownLanguage.rust)
+    ) {
       const feat = Feature.RustAnalysis;
       const minVer = featureConfig[feat].minimumVersion as string;
       const envVar = "CODEQL_ENABLE_EXPERIMENTAL_FEATURES";