refactor(builder): floor mtime inside fileStat helper (#1080)

Encapsulate `Math.floor(stat.mtimeMs)` inside the `fileStat` helper so
every consumer of the integer DB column gets a pre-floored value by
default. Eliminates the risk that a future call site reads
`stat.mtimeMs` and stores it un-floored, which would silently write a
non-integer (or rounded-up integer) into the DB and cause spurious
fast-skip misses on the next build.

All six existing call sites simplified from `Math.floor(stat.mtimeMs)`
to `stat.mtime`. Behaviour unchanged.

Addresses Greptile P2 feedback on the revert PR.

Author: carlos-alm

src/domain/graph/builder/helpers.ts

@@ -222,12 +222,17 @@ export function fileHash(content: string): string {
 }
 
 /**
- * Stat a file, returning { mtimeMs, size } or null on error.
+ * Stat a file, returning { mtime, size } or null on error.
+ *
+ * `mtime` is `Math.floor(stat.mtimeMs)` so it matches the integer column
+ * stored in the DB. Floor-once-here keeps every consumer honest: storing or
+ * comparing a non-floored `mtimeMs` against the integer DB column would cause
+ * spurious fast-skip misses on the next build.
  */
-export function fileStat(filePath: string): { mtimeMs: number; size: number } | null {
+export function fileStat(filePath: string): { mtime: number; size: number } | null {
   try {
     const s = fs.statSync(filePath);
-    return { mtimeMs: s.mtimeMs, size: s.size };
+    return { mtime: Math.floor(s.mtimeMs), size: s.size };
   } catch {
     return null;
   }

src/domain/graph/builder/pipeline.ts

@@ -938,7 +938,7 @@ async function backfillNativeDroppedFiles(ctx: PipelineContext): Promise<void> {
         }
         if (code === null) continue;
         const stat = fileStat(absPath);
-        const mtime = stat ? Math.floor(stat.mtimeMs) : 0;
+        const mtime = stat ? stat.mtime : 0;
         const size = stat ? stat.size : 0;
         upsertHash.run(relPath, fileHash(code), mtime, size);
       }

src/domain/graph/builder/stages/detect-changes.ts

@@ -27,7 +27,7 @@ interface FileHashRow {
 }
 
 interface FileStat {
-  mtimeMs: number;
+  mtime: number;
   size: number;
 }
 
@@ -182,7 +182,7 @@ function mtimeAndHashTiers(
     if (!stat) continue;
     const storedMtime = record.mtime || 0;
     const storedSize = record.size || 0;
-    if (storedSize > 0 && Math.floor(stat.mtimeMs) === storedMtime && stat.size === storedSize) {
+    if (storedSize > 0 && stat.mtime === storedMtime && stat.size === storedSize) {
       skipped.push(relPath);
       continue;
     }
@@ -596,9 +596,9 @@ export function detectNoChanges(
       log(`false: stored size <= 0 for ${relPath} (stored=${record.size})`);
       return false;
     }
-    if (Math.floor(stat.mtimeMs) !== storedMtime || stat.size !== storedSize) {
+    if (stat.mtime !== storedMtime || stat.size !== storedSize) {
       log(
-        `false: mtime/size diff for ${relPath}: stat=${Math.floor(stat.mtimeMs)}/${stat.size} stored=${storedMtime}/${storedSize} (mtimeMs=${stat.mtimeMs})`,
+        `false: mtime/size diff for ${relPath}: stat=${stat.mtime}/${stat.size} stored=${storedMtime}/${storedSize}`,
       );
       return false;
     }
@@ -663,7 +663,7 @@ export async function detectChanges(ctx: PipelineContext): Promise<void> {
         relPath: c.relPath,
         content: c.content,
         hash: c.hash,
-        stat: c.stat ? { mtime: Math.floor(c.stat.mtimeMs), size: c.stat.size } : undefined,
+        stat: c.stat ? { mtime: c.stat.mtime, size: c.stat.size } : undefined,
         _reverseDepOnly: c._reverseDepOnly,
       }));
     ctx.metadataUpdates = increResult.changed
@@ -674,7 +674,7 @@ export async function detectChanges(ctx: PipelineContext): Promise<void> {
       .map((c) => ({
         relPath: c.relPath,
         hash: c.hash,
-        stat: { mtime: Math.floor(c.stat.mtimeMs), size: c.stat.size },
+        stat: { mtime: c.stat.mtime, size: c.stat.size },
       }));
     if (!ctx.isFullBuild && ctx.parseChanges.length === 0 && ctx.removed.length === 0) {
       const ranAnalysis = await runPendingAnalysis(ctx);

src/domain/graph/builder/stages/insert-nodes.ts

@@ -128,7 +128,7 @@ export function buildFileHashes(
         size = precomputed.stat.size;
       } else {
         const rawStat = fileStat(path.join(rootDir, relPath));
-        mtime = rawStat ? Math.floor(rawStat.mtimeMs) : 0;
+        mtime = rawStat ? rawStat.mtime : 0;
         size = rawStat ? rawStat.size : 0;
       }
       fileHashes.push({ file: relPath, hash: precomputed.hash, mtime, size });
@@ -143,7 +143,7 @@ export function buildFileHashes(
       }
       if (code !== null) {
         const stat = fileStat(absPath);
-        const mtime = stat ? Math.floor(stat.mtimeMs) : 0;
+        const mtime = stat ? stat.mtime : 0;
         const size = stat ? stat.size : 0;
         fileHashes.push({ file: relPath, hash: fileHash(code), mtime, size });
       }
@@ -152,7 +152,7 @@ export function buildFileHashes(
 
   // Also include metadata-only updates (self-heal mtime/size without re-parse)
   for (const item of metadataUpdates) {
-    const mtime = item.stat ? Math.floor(item.stat.mtime) : 0;
+    const mtime = item.stat ? item.stat.mtime : 0;
     const size = item.stat ? item.stat.size : 0;
     fileHashes.push({ file: item.relPath, hash: item.hash, mtime, size });
   }
@@ -365,7 +365,7 @@ function updateFileHashes(
         size = precomputed.stat.size;
       } else {
         const rawStat = fileStat(path.join(rootDir, relPath));
-        mtime = rawStat ? Math.floor(rawStat.mtimeMs) : 0;
+        mtime = rawStat ? rawStat.mtime : 0;
         size = rawStat ? rawStat.size : 0;
       }
       upsertHash.run(relPath, precomputed.hash, mtime, size);
@@ -380,7 +380,7 @@ function updateFileHashes(
       }
       if (code !== null) {
         const stat = fileStat(absPath);
-        const mtime = stat ? Math.floor(stat.mtimeMs) : 0;
+        const mtime = stat ? stat.mtime : 0;
         const size = stat ? stat.size : 0;
         upsertHash.run(relPath, fileHash(code), mtime, size);
       }
@@ -389,7 +389,7 @@ function updateFileHashes(
 
   // Also update metadata-only entries (self-heal mtime/size without re-parse)
   for (const item of metadataUpdates) {
-    const mtime = item.stat ? Math.floor(item.stat.mtime) : 0;
+    const mtime = item.stat ? item.stat.mtime : 0;
     const size = item.stat ? item.stat.size : 0;
     upsertHash.run(item.relPath, item.hash, mtime, size);
   }