Consume precomputed diff ranges in analyze

Author: alexet

lib/analyze-action.js

@@ -30,7 +30,6 @@ import {
   DependencyCacheUploadStatusReport,
   uploadDependencyCaches,
 } from "./dependency-caching";
-import { getDiffInformedAnalysisBranches } from "./diff-informed-analysis-utils";
 import { EnvVar } from "./environment";
 import { Feature, Features } from "./feature-flags";
 import { KnownLanguage } from "./languages";
@@ -302,14 +301,8 @@ async function run() {
       logger,
     );
 
-    const branches = await getDiffInformedAnalysisBranches(
-      codeql,
-      features,
-      logger,
-    );
-    const diffRangePackDir = branches
-      ? await setupDiffInformedQueryRun(branches, logger)
-      : undefined;
+    // Setup diff informed analysis if needed (based on whether init created the file)
+    const diffRangePackDir = await setupDiffInformedQueryRun(logger);
 
     await warnIfGoInstalledAfterInit(config, logger);
     await runAutobuildIfLegacyGoWorkflow(config, logger);

src/analyze-action.ts

@@ -6,7 +6,7 @@ import * as io from "@actions/io";
 import * as del from "del";
 import * as yaml from "js-yaml";
 
-import { getTemporaryDirectory, PullRequestBranches } from "./actions-util";
+import { getTemporaryDirectory } from "./actions-util";
 import * as analyses from "./analyses";
 import { setupCppAutobuild } from "./autobuild";
 import { type CodeQL } from "./codeql";
@@ -15,8 +15,7 @@ import { getJavaTempDependencyDir } from "./dependency-caching";
 import { addDiagnostic, makeDiagnostic } from "./diagnostics";
 import {
   DiffThunkRange,
-  writeDiffRangesJsonFile,
-  getPullRequestEditedDiffRanges,
+  readDiffRangesJsonFile,
 } from "./diff-informed-analysis-utils";
 import { EnvVar } from "./environment";
 import { FeatureEnablement, Feature } from "./feature-flags";
@@ -282,16 +281,36 @@ async function finalizeDatabaseCreation(
  * the diff range information, or `undefined` if the feature is disabled.
  */
 export async function setupDiffInformedQueryRun(
-  branches: PullRequestBranches,
   logger: Logger,
 ): Promise<string | undefined> {
   return await withGroupAsync(
     "Generating diff range extension pack",
     async () => {
+      // Only use precomputed diff ranges; never recompute here.
+      let diffRanges: DiffThunkRange[] | undefined;
+      try {
+        diffRanges = readDiffRangesJsonFile(logger);
+      } catch (e) {
+        logger.debug(
+          `Failed to read precomputed diff ranges: ${util.getErrorMessage(e)}`,
+        );
+        diffRanges = undefined;
+      }
+
+      if (diffRanges === undefined) {
+        logger.info(
+          "No precomputed diff ranges found; skipping diff-informed analysis stage.",
+        );
+        return undefined;
+      }
+
+      const fileCount = new Set(
+        diffRanges.filter((r) => r.path).map((r) => r.path),
+      ).size;
       logger.info(
-        `Calculating diff ranges for ${branches.base}...${branches.head}`,
+        `Using precomputed diff ranges (${diffRanges.length} ranges across ${fileCount} files).`,
       );
-      const diffRanges = await getPullRequestEditedDiffRanges(branches, logger);
+
       const packDir = writeDiffRangeDataExtensionPack(logger, diffRanges);
       if (packDir === undefined) {
         logger.warning(
@@ -388,10 +407,6 @@ extensions:
     `Wrote pr-diff-range extension pack to ${extensionFilePath}:\n${extensionContents}`,
   );
 
-  // Write the diff ranges to a JSON file, for action-side alert filtering by the
-  // upload-lib module.
-  writeDiffRangesJsonFile(logger, ranges);
-
   return diffRangeDir;
 }