fix(heft-lint-plugin): allow ESLint linter output to be cached (#5107)

Signed-off-by: Aramis Sennyey <[email protected]>
Co-authored-by: Aramis Sennyey <[email protected]>

Author: aramissennyeydd

common/changes/@rushstack/heft-lint-plugin/sennyeya-fix-eslint-caching_2025-02-13-15-00.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@rushstack/heft-lint-plugin",
+      "comment": "Fix an issue where the cache is only populated for incremental TypeScript builds.",
+      "type": "patch"
+    }
+  ],
+  "packageName": "@rushstack/heft-lint-plugin"
+}

heft-plugins/heft-lint-plugin/src/Eslint.ts

@@ -176,7 +176,14 @@ export class Eslint extends LinterBase<TEslint.ESLint.LintResult> {
           return lintResult.fixableErrorCount + lintResult.fixableWarningCount > 0;
         }));
 
-    return lintResults;
+    const trimmedLintResults: TEslint.ESLint.LintResult[] = [];
+    for (const lintResult of lintResults) {
+      if (lintResult.messages.length > 0 || lintResult.warningCount > 0 || lintResult.errorCount > 0) {
+        trimmedLintResults.push(lintResult);
+      }
+    }
+
+    return trimmedLintResults;
   }
 
   protected async lintingFinishedAsync(lintResults: TEslint.ESLint.LintResult[]): Promise<void> {

heft-plugins/heft-lint-plugin/src/LinterBase.ts

@@ -138,8 +138,15 @@ export abstract class LinterBase<TLintResult> {
         continue;
       }
 
-      // Compute the version from the source file content
-      const version: string = sourceFile.version || '';
+      // TypeScript only computes the version during an incremental build.
+      let version: string = sourceFile.version;
+      if (!version) {
+        // Compute the version from the source file content
+        const sourceCodeHash: Hash = createHash('sha1');
+        sourceCodeHash.update(sourceFile.text);
+        version = sourceCodeHash.digest('base64');
+      }
+
       const cachedVersion: string = cachedNoFailureFileVersions.get(relative) || '';
       if (
         cachedVersion === '' ||