fix(schema-pack): narrow stats catch-all so masked errors surface, not fake 0 pages (#2466)

fetchCountRows and detectDeadPrefixes in src/core/schema-pack/stats.ts
swallowed EVERY engine error into empty results, so any real failure
printed 'Total pages: 0' + a vacuous 100% coverage on a populated brain.
Both catches now swallow only isUndefinedTableError (pre-init brain,
missing pages table) and rethrow everything else. Four regression tests:
real non-zero count on a populated PGLite brain, rethrow on non-missing-
table errors in both catch sites, and the missing-table degrade path.

Takeover of #2493.

Co-authored-by: javieraldape <javieraldape@users.noreply.github.com>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/core/schema-pack/stats.ts

@@ -18,6 +18,7 @@
 import type { BrainEngine } from '../engine.ts';
 import { loadActivePackBestEffort } from './best-effort.ts';
 import type { OperationContext } from '../operations.ts';
+import { isUndefinedTableError } from '../utils.ts';
 
 export interface StatsOpts {
   /** Single source scope. Omit + omit sourceIds for whole-brain aggregate. */
@@ -164,9 +165,17 @@ async function fetchCountRows(engine: BrainEngine, opts: StatsOpts): Promise<Raw
   `;
   try {
     return await engine.executeRaw<RawCountRow>(sql, params);
-  } catch {
-    // Empty / pre-init brain: pages table may not exist yet.
-    return [];
+  } catch (err) {
+    // ONLY swallow the genuine "pages table doesn't exist yet" case
+    // (empty / pre-init brain). #2466: the old bare `catch {}` masked
+    // EVERY error — so any engine-level failure (connection, version
+    // skew, a query incompatibility) was silently converted to 0 rows,
+    // printing "Total pages: 0" on a populated brain and cascading into
+    // false "100% coverage" + a starved `schema suggest`. Surface
+    // everything that is not a missing-table error so the real failure
+    // is visible instead of hidden behind a fake zero.
+    if (isUndefinedTableError(err)) return [];
+    throw err;
   }
 }
 
@@ -204,9 +213,11 @@ async function detectDeadPrefixes(
         if (cnt === 0) {
           hints.push({ type: t.name, prefix });
         }
-      } catch {
-        // Skip on engine error (no pages table yet, etc.).
-        continue;
+      } catch (err) {
+        // #2466: only skip on the genuine "no pages table yet" case;
+        // rethrow any other engine error so it isn't silently masked.
+        if (isUndefinedTableError(err)) continue;
+        throw err;
       }
     }
   }

test/schema-pack-stats.test.ts

@@ -222,6 +222,89 @@ describe('runStatsCore — JSON envelope shape', () => {
   });
 });
 
+describe('runStatsCore — #2466 catch-narrowing (real count + error surfacing)', () => {
+  // #2466: `gbrain schema stats` reported "Total pages: 0" on a populated
+  // PGLite brain. The bug was a bare `catch {}` in fetchCountRows (and a
+  // sibling in detectDeadPrefixes) that converted ANY engine error into 0
+  // rows. The COUNT query itself is valid on PGLite (proven below), so the
+  // regression pins two things: (a) a populated brain reports the real,
+  // non-zero count through the full runStatsCore path; (b) a non-missing-
+  // table engine error is rethrown, not masked into a fake zero.
+
+  it('reports the real non-zero count on a populated PGLite brain (no false 0)', async () => {
+    await withEnv({ GBRAIN_SCHEMA_PACK: undefined }, async () => {
+      // Seed a realistic mix: typed, untyped, multiple types — like the
+      // 169-page brain in the bug report (scaled down).
+      for (let i = 0; i < 12; i++) {
+        const type = i % 3 === 0 ? '' : (i % 3 === 1 ? 'person' : 'company');
+        await seedPage(`notes/p${i}`, { type, sourcePath: `notes/p${i}.md` });
+      }
+      const result = await runStatsCore(ctxOf());
+      // The core regression: NOT zero.
+      expect(result.aggregate.total_pages).toBe(12);
+      expect(result.aggregate.typed_pages).toBe(8);
+      expect(result.aggregate.untyped_pages).toBe(4);
+      // And coverage is the honest ratio, not the vacuous 1.0 a 0/0 prints.
+      expect(result.aggregate.coverage).not.toBe(1.0);
+    });
+  });
+
+  it('fetchCountRows rethrows a non-missing-table engine error instead of masking it as 0 pages', async () => {
+    await withEnv({ GBRAIN_SCHEMA_PACK: undefined }, async () => {
+      // No pack → detectDeadPrefixes is skipped, isolating the throw to the
+      // fetchCountRows catch we narrowed. The count query (the GROUP BY one)
+      // throws a column-level error (SQLSTATE 42703) — the exact class the
+      // old bare `catch {}` swallowed into 0 rows; everything else succeeds.
+      __setPackLocatorForTests(() => null);
+      const boom = Object.assign(new Error('column "type" does not exist'), { code: '42703' });
+      const stubEngine = {
+        executeRaw: async (sql: string) => {
+          if (/GROUP BY source_id/.test(sql)) throw boom;  // the fetchCountRows query
+          return [];
+        },
+      } as unknown as PGLiteEngine;
+      const ctx = { ...ctxOf(), engine: stubEngine } as unknown as OperationContext;
+      await expect(runStatsCore(ctx)).rejects.toThrow('column "type" does not exist');
+    });
+  });
+
+  it('fetchCountRows still degrades to empty (no throw) on a genuine missing pages table', async () => {
+    await withEnv({ GBRAIN_SCHEMA_PACK: undefined }, async () => {
+      // Pre-init brain shape: the count query hits a missing pages table
+      // (SQLSTATE 42P01). This is the ONLY case the narrowed catch swallows.
+      __setPackLocatorForTests(() => null);
+      const missing = Object.assign(new Error('relation "pages" does not exist'), { code: '42P01' });
+      const stubEngine = {
+        executeRaw: async (sql: string) => {
+          if (/GROUP BY source_id/.test(sql)) throw missing;
+          return [];
+        },
+      } as unknown as PGLiteEngine;
+      const ctx = { ...ctxOf(), engine: stubEngine } as unknown as OperationContext;
+      const result = await runStatsCore(ctx);
+      expect(result.aggregate.total_pages).toBe(0);
+      expect(result.per_source).toEqual([]);
+    });
+  });
+
+  it('detectDeadPrefixes rethrows a non-missing-table error (sibling catch)', async () => {
+    await withEnv({ GBRAIN_HOME: tmpDir, GBRAIN_SCHEMA_PACK: 'tiny' }, async () => {
+      seedTinyPack('tiny', [{ name: 'person', prefix: 'people/' }]);
+      // fetchCountRows (the GROUP BY query) succeeds → []; the per-prefix
+      // dead-prefix LIKE query then throws a non-missing-table error, which
+      // must surface through the narrowed sibling catch.
+      const stubEngine = {
+        executeRaw: async (sql: string) => {
+          if (/GROUP BY source_id/.test(sql)) return [];        // count query: empty brain, fine
+          throw Object.assign(new Error('division by zero'), { code: '22012' });  // the LIKE query
+        },
+      } as unknown as PGLiteEngine;
+      const ctx = { ...ctxOf(), engine: stubEngine } as unknown as OperationContext;
+      await expect(runStatsCore(ctx)).rejects.toThrow('division by zero');
+    });
+  });
+});
+
 describe('runStatsCore — type/untyped split', () => {
   it('treats empty-string type as untyped (not its own bucket)', async () => {
     await withEnv({ GBRAIN_SCHEMA_PACK: undefined }, async () => {