feat(enrichment): add empty-catch / error-swallow analyzer

Fixes #2014 — flags swallowed errors in added JS/TS/Python catch/except blocks.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: bohdansolovie

.env.example

@@ -65,25 +65,26 @@ GITTENSORY_REVIEW_ENRICHMENT=false
 # Current analyzer names:
 # dependency,lockfileDrift,secret,license,installScript,heavyDependency,hardcodedUrl,actionPin
 # eol,redos,provenance,codeowners,secretLog,assetWeight,typosquat,commitSignature,iacMisconfig
-# nativeBuild,history,docCommentDrift,duplication,churnHotspot,blameLink,approvalIntegrity
-# ciCheckSignals,undocumentedExport,staleBranch,commitHygiene,pendingReviewRequests,testRatio
-# migrationSafety,looseRange,terminology,todoMarker,magicNumber,conflictMarker,debugLeftover
-# commitLint
+# nativeBuild,history,docCommentDrift,duplication,errorSwallow,churnHotspot,blameLink
+# approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch,commitHygiene
+# pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology,todoMarker,magicNumber
+# conflictMarker,debugLeftover,commitLint
 #
 # Profile defaults:
 # fast: dependency,lockfileDrift,secret,license,installScript,heavyDependency,hardcodedUrl
-# actionPin,eol,redos,provenance,secretLog,typosquat,iacMisconfig,nativeBuild,testRatio
-# migrationSafety,looseRange,terminology,todoMarker,magicNumber,conflictMarker,debugLeftover
+# actionPin,eol,redos,provenance,secretLog,typosquat,iacMisconfig,nativeBuild,errorSwallow
+# testRatio,migrationSafety,looseRange,terminology,todoMarker,magicNumber,conflictMarker
+# debugLeftover
 # balanced (default): dependency,lockfileDrift,secret,license,installScript,heavyDependency
 # hardcodedUrl,actionPin,eol,redos,provenance,codeowners,secretLog,assetWeight,typosquat
-# commitSignature,iacMisconfig,nativeBuild,history,docCommentDrift,duplication,churnHotspot
-# blameLink,approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch,commitHygiene
-# pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology,todoMarker,magicNumber
-# conflictMarker,debugLeftover,commitLint
+# commitSignature,iacMisconfig,nativeBuild,history,docCommentDrift,duplication,errorSwallow
+# churnHotspot,blameLink,approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch
+# commitHygiene,pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology
+# todoMarker,magicNumber,conflictMarker,debugLeftover,commitLint
 # deep: dependency,lockfileDrift,secret,license,installScript,heavyDependency,hardcodedUrl
 # actionPin,eol,redos,provenance,codeowners,secretLog,assetWeight,typosquat,commitSignature
-# iacMisconfig,nativeBuild,history,docCommentDrift,duplication,churnHotspot,blameLink
-# approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch,commitHygiene
+# iacMisconfig,nativeBuild,history,docCommentDrift,duplication,errorSwallow,churnHotspot
+# blameLink,approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch,commitHygiene
 # pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology,todoMarker,magicNumber
 # conflictMarker,debugLeftover,commitLint
 # END GENERATED REES ANALYZERS

apps/gittensory-ui/src/lib/rees-analyzers.ts

@@ -559,6 +559,28 @@ export const REES_ANALYZERS = [
         "Conservative: trivial/boilerplate lines are dropped and a long contiguous run is required, so incidental overlap is not flagged. Never returns code content.",
     },
   },
+  {
+    name: "errorSwallow",
+    title: "Swallowed errors",
+    category: "quality",
+    cost: "local",
+    defaultEnabled: true,
+    profiles: ["fast", "balanced", "deep"],
+    requires: ["files"],
+    limits: {
+      maxFindings: 25,
+      maxLineChars: 2000,
+    },
+    docs: {
+      summary:
+        "Flags newly-added catch/except blocks that swallow errors without logging or rethrowing.",
+      looksAt: "Added lines in changed JS/TS/Python source files, excluding tests.",
+      reports: "File, line, and kind: empty-catch, unused-binding, or return-null.",
+      network: "Pure local analyzer. No external network call.",
+      notes:
+        "Precision-first: catches that log, rethrow, or reference the binding are not flagged. Python `except: pass` is included.",
+    },
+  },
   {
     name: "churnHotspot",
     title: "Churn hotspots",

review-enrichment/analyzer-metadata.json

@@ -637,6 +637,32 @@
         "notes": "Conservative: trivial/boilerplate lines are dropped and a long contiguous run is required, so incidental overlap is not flagged. Never returns code content."
       }
     },
+    {
+      "name": "errorSwallow",
+      "title": "Swallowed errors",
+      "category": "quality",
+      "cost": "local",
+      "defaultEnabled": true,
+      "profiles": [
+        "fast",
+        "balanced",
+        "deep"
+      ],
+      "requires": [
+        "files"
+      ],
+      "limits": {
+        "maxFindings": 25,
+        "maxLineChars": 2000
+      },
+      "docs": {
+        "summary": "Flags newly-added catch/except blocks that swallow errors without logging or rethrowing.",
+        "looksAt": "Added lines in changed JS/TS/Python source files, excluding tests.",
+        "reports": "File, line, and kind: empty-catch, unused-binding, or return-null.",
+        "network": "Pure local analyzer. No external network call.",
+        "notes": "Precision-first: catches that log, rethrow, or reference the binding are not flagged. Python `except: pass` is included."
+      }
+    },
     {
       "name": "churnHotspot",
       "title": "Churn hotspots",

review-enrichment/src/analyzers/error-swallow.ts

@@ -0,0 +1,175 @@
+// Empty-catch / error-swallow analyzer (#2014). Flags newly-added catch/except blocks that swallow the error
+// (empty body, unused binding, or a bare `return null`) — a top source of silent failures. Pure compute over
+// added diff lines, no network. Scoped to JS/TS/Python source files; Python `except: pass` is included.
+import type { EnrichRequest, ErrorSwallowFinding } from "../types.js";
+import { isTestPath } from "./test-ratio.js";
+
+const MAX_FINDINGS = 25;
+const MAX_LINE_CHARS = 2000;
+
+const SOURCE_EXTS = new Set(["ts", "tsx", "js", "jsx", "mjs", "cjs", "mts", "cts", "py"]);
+
+const CATCH_OPEN_RE = /catch\s*\(\s*(\w+)?\s*\)\s*\{/;
+const SINGLE_CATCH_RE = /catch\s*\(\s*(\w+)?\s*\)\s*\{([\s\S]*?)\}/;
+const PY_EXCEPT_PASS_RE = /^\s*except(?:\s+[\w.]+\s*(?:as\s+(\w+))?)?\s*:\s*pass\s*(?:#.*)?$/;
+
+function isScannablePath(path: string): boolean {
+  const ext = /\.([^.]+)$/.exec(path)?.[1]?.toLowerCase();
+  return Boolean(ext && SOURCE_EXTS.has(ext) && !isTestPath(path));
+}
+
+function escapeRegExp(value: string): string {
+  return value.replace(/[$.*+?^{}()|[\]\\]/g, "\\$&");
+}
+
+function bodySwallowsError(body: string, binding: string | null): ErrorSwallowFinding["kind"] | null {
+  const trimmed = body.trim();
+  if (!trimmed) return "empty-catch";
+  if (/^return\s+null\s*;?$/.test(trimmed)) return "return-null";
+  if (!binding) return null;
+  const bindingRe = new RegExp(`\\b${escapeRegExp(binding)}\\b`);
+  if (/\bthrow\b/.test(trimmed)) return null;
+  if (/\b(?:console|logger|log|winston|pino|bunyan)\s*[.(]/.test(trimmed)) return null;
+  if (/\bprint\s*\(/.test(trimmed)) return null;
+  if (!bindingRe.test(trimmed)) return "unused-binding";
+  return null;
+}
+
+/** Classify one source line for an error-swallow pattern, or null. Pure. */
+export function detectErrorSwallow(line: string): ErrorSwallowFinding["kind"] | null {
+  const pyMatch = PY_EXCEPT_PASS_RE.exec(line);
+  if (pyMatch) {
+    return pyMatch[1] ? "unused-binding" : "empty-catch";
+  }
+
+  const single = SINGLE_CATCH_RE.exec(line);
+  if (single) {
+    return bodySwallowsError(single[2] ?? "", single[1] ?? null);
+  }
+
+  return null;
+}
+
+type PendingCatch = {
+  startLine: number;
+  binding: string | null;
+  body: string;
+  depth: number;
+};
+
+function updatePending(pending: PendingCatch, line: string): PendingCatch {
+  let depth = pending.depth;
+  for (const ch of line) {
+    if (ch === "{") depth++;
+    else if (ch === "}") depth--;
+  }
+  return { ...pending, body: `${pending.body}\n${line}`, depth };
+}
+
+function flushPending(pending: PendingCatch): ErrorSwallowFinding["kind"] | null {
+  const body = pending.body.replace(/^\s*\{/, "").replace(/\}\s*$/, "");
+  return bodySwallowsError(body, pending.binding);
+}
+
+type ScanLimits = {
+  maxFindings?: number;
+  signal?: AbortSignal;
+};
+
+/** Scan one file patch's added lines for swallowed errors, line-cited via hunk headers. Pure. */
+export function scanPatchForErrorSwallow(
+  path: string,
+  patch: string,
+  limits: ScanLimits = {},
+): ErrorSwallowFinding[] {
+  const maxFindings = limits.maxFindings ?? MAX_FINDINGS;
+  if (maxFindings <= 0 || !isScannablePath(path)) return [];
+  const findings: ErrorSwallowFinding[] = [];
+  let newLine = 0;
+  let inHunk = false;
+  let pending: PendingCatch | null = null;
+
+  const pushFinding = (line: number, kind: ErrorSwallowFinding["kind"]) => {
+    findings.push({ file: path, line, kind });
+  };
+
+  for (const line of patch.split("\n")) {
+    if (limits.signal?.aborted) throw new Error("analyzer_aborted");
+    const hunk = /^@@ -\d+(?:,\d+)? \+(\d+)(?:,\d+)? @@/.exec(line);
+    if (hunk) {
+      newLine = Number(hunk[1]);
+      inHunk = true;
+      pending = null;
+      continue;
+    }
+    if (!inHunk) continue;
+
+    if (line.startsWith("+")) {
+      const body = line.slice(1);
+      if (body.length <= MAX_LINE_CHARS) {
+        if (pending) {
+          pending = updatePending(pending, body);
+          if (pending.depth <= 0) {
+            const kind = flushPending(pending);
+            if (kind) pushFinding(pending.startLine, kind);
+            pending = null;
+          }
+        } else {
+          const kind = detectErrorSwallow(body);
+          if (kind) {
+            pushFinding(newLine, kind);
+            if (findings.length >= maxFindings) return findings;
+          } else {
+            const open = CATCH_OPEN_RE.exec(body);
+            if (open) {
+              const braceIndex = body.indexOf("{", open.index ?? 0);
+              if (braceIndex >= 0 && !body.slice(braceIndex + 1).includes("}")) {
+                let depth = 0;
+                for (const ch of body.slice(braceIndex)) {
+                  if (ch === "{") depth++;
+                  else if (ch === "}") depth--;
+                }
+                pending = {
+                  startLine: newLine,
+                  binding: open[1] ?? null,
+                  body: body.slice(braceIndex),
+                  depth,
+                };
+              }
+            }
+          }
+        }
+      }
+      newLine++;
+    } else if (!line.startsWith("-") && !line.startsWith("\\")) {
+      pending = null;
+      newLine++;
+    } else {
+      pending = null;
+    }
+
+    if (findings.length >= maxFindings) return findings;
+  }
+
+  return findings;
+}
+
+/** Analyzer entrypoint: scan every changed scannable file's added lines for swallowed errors. */
+export async function scanErrorSwallow(
+  req: EnrichRequest,
+  signal?: AbortSignal,
+): Promise<ErrorSwallowFinding[]> {
+  const findings: ErrorSwallowFinding[] = [];
+  for (const file of req.files ?? []) {
+    if (signal?.aborted) throw new Error("analyzer_aborted");
+    if (!file.patch) continue;
+    for (const finding of scanPatchForErrorSwallow(file.path, file.patch, {
+      maxFindings: MAX_FINDINGS - findings.length,
+      signal,
+    })) {
+      findings.push(finding);
+      if (findings.length >= MAX_FINDINGS) return findings;
+    }
+  }
+  return findings;
+}

review-enrichment/src/analyzers/registry.ts

@@ -10,6 +10,7 @@ import { scanCommitSignature } from "./commit-signature.js";
 import { dependencyAnalyzer } from "./dependency/descriptor.js";
 import { scanDocCommentDrift } from "./doc-comment-drift.js";
 import { scanDuplication } from "./duplication-scan.js";
+import { scanErrorSwallow } from "./error-swallow.js";
 import { scanEol } from "./eol-check.js";
 import { scanHardcodedUrl } from "./hardcoded-url.js";
 import { scanHeavyDependencies } from "./heavy-dependency.js";
@@ -466,6 +467,35 @@ export const ANALYZER_DESCRIPTORS = [
     run: (req, { signal, analysis, diagnostics }) =>
       scanDuplication(req, fetch, { signal, analysis, diagnostics }),
   }),
+  descriptor({
+    name: "errorSwallow",
+    title: "Swallowed errors",
+    category: "quality",
+    cost: "local",
+    defaultEnabled: true,
+    requires: ["files"],
+    limits: { maxFindings: 25, maxLineChars: 2000 },
+    docs: {
+      summary:
+        "Flags newly-added catch/except blocks that swallow errors without logging or rethrowing.",
+      looksAt: "Added lines in changed JS/TS/Python source files, excluding tests.",
+      reports: "File, line, and kind: empty-catch, unused-binding, or return-null.",
+      network: "Pure local analyzer. No external network call.",
+      notes:
+        "Precision-first: catches that log, rethrow, or reference the binding are not flagged. Python `except: pass` is included.",
+    },
+    render: (findings, helpers) => {
+      if (!findings.length) return [];
+      const lines = ["### Swallowed errors (empty catch / unused binding / return null)"];
+      for (const item of findings) {
+        lines.push(
+          `- ${helpers.safeCodeSpan(`${item.file}:${item.line}`)} — ${helpers.safeCodeSpan(item.kind)}`,
+        );
+      }
+      return lines;
+    },
+    run: (req, { signal }) => scanErrorSwallow(req, signal),
+  }),
   descriptor({
     name: "churnHotspot",
     title: "Churn hotspots",

review-enrichment/src/render.ts

@@ -481,6 +481,7 @@ export function renderBrief(
   lines.push(...renderDescriptorSection("magicNumber", findings.magicNumber));
   lines.push(...renderDescriptorSection("conflictMarker", findings.conflictMarker));
   lines.push(...renderDescriptorSection("debugLeftover", findings.debugLeftover));
+  lines.push(...renderDescriptorSection("errorSwallow", findings.errorSwallow));
   lines.push(...renderDescriptorSection("hardcodedUrl", findings.hardcodedUrl));
   lines.push(...renderDescriptorSection("commitLint", findings.commitLint));
 

review-enrichment/src/types.ts

@@ -482,6 +482,14 @@ export interface HardcodedUrlFinding {
   host: string;
 }
 
+/** A newly-added catch/except block that swallows an error without logging or rethrowing (#2014, part of #1499).
+ *  Reports location and kind only — never catch bodies or stack traces. */
+export interface ErrorSwallowFinding {
+  file: string;
+  line: number;
+  kind: "empty-catch" | "unused-binding" | "return-null";
+}
+
 /** A PR commit subject that does not conform to the Conventional Commits spec (#2021, part of #1499). Reports a
  *  short SHA prefix, the subject, and the failing reason — never author/email. */
 export interface CommitLintFinding {
@@ -529,6 +537,7 @@ export interface BriefFindings {
   conflictMarker?: ConflictMarkerFinding[];
   debugLeftover?: DebugLeftoverFinding[];
   hardcodedUrl?: HardcodedUrlFinding[];
+  errorSwallow?: ErrorSwallowFinding[];
   commitLint?: CommitLintFinding[];
 }
 

review-enrichment/test/analyzer-registry.test.ts

@@ -31,6 +31,7 @@ const EXPECTED_ANALYZERS = [
   "history",
   "docCommentDrift",
   "duplication",
+  "errorSwallow",
   "churnHotspot",
   "blameLink",
   "approvalIntegrity",