fix: merge monthly counts into existing state instead of overwriting (#538)

* fix: merge monthly counts into existing state instead of overwriting

When updateMonthlyAnalytics() stored fresh API results, it replaced the
entire monthlyMergedCounts/monthlyClosedCounts/monthlyOpenedCounts objects.
If the GitHub Search API returned only recent months (due to pagination
limits, caching, or incomplete results), all historical months were lost.

Now fresh API data is merged into existing state: months present in the
API response are updated, months only in existing state are preserved.

Fixes #537

* style: fix prettier formatting

* ci: add pre-commit hook for prettier format check

Author: costajohnt

package.json

@@ -20,6 +20,7 @@
     "prepare": "[ -n \"$CI\" ] || simple-git-hooks"
   },
   "simple-git-hooks": {
+    "pre-commit": "pnpm format:check",
     "commit-msg": "./scripts/commit-msg.sh \"$1\""
   },
   "keywords": [

packages/core/src/commands/dashboard-data.test.ts

@@ -3,7 +3,13 @@
  */
 
 import { describe, it, expect } from 'vitest';
-import { buildDashboardStats, computePRsByRepo, computeTopRepos, getMonthlyData } from './dashboard-data.js';
+import {
+  buildDashboardStats,
+  computePRsByRepo,
+  computeTopRepos,
+  getMonthlyData,
+  mergeMonthlyCounts,
+} from './dashboard-data.js';
 import type { DailyDigest, AgentState, ShelvedPRRef } from '../core/types.js';
 
 function makeDigest(overrides: Partial<DailyDigest> = {}): DailyDigest {
@@ -276,3 +282,46 @@ describe('getMonthlyData', () => {
     expect(result.monthlyOpened).toEqual({});
   });
 });
+
+describe('mergeMonthlyCounts', () => {
+  it('preserves existing months not in fresh data', () => {
+    const existing = { '2025-06': 9, '2025-07': 26, '2026-01': 11 };
+    const fresh = { '2026-02': 14, '2026-03': 4 };
+    const result = mergeMonthlyCounts(existing, fresh);
+    expect(result).toEqual({
+      '2025-06': 9,
+      '2025-07': 26,
+      '2026-01': 11,
+      '2026-02': 14,
+      '2026-03': 4,
+    });
+  });
+
+  it('updates existing months when fresh data has them', () => {
+    const existing = { '2026-02': 10, '2026-03': 2 };
+    const fresh = { '2026-02': 14, '2026-03': 4 };
+    const result = mergeMonthlyCounts(existing, fresh);
+    expect(result).toEqual({ '2026-02': 14, '2026-03': 4 });
+  });
+
+  it('returns copy of existing when fresh is empty', () => {
+    const existing = { '2025-06': 9, '2025-07': 26 };
+    const result = mergeMonthlyCounts(existing, {});
+    expect(result).toEqual(existing);
+    expect(result).not.toBe(existing);
+  });
+
+  it('returns fresh data when existing is empty', () => {
+    const fresh = { '2026-02': 14, '2026-03': 4 };
+    const result = mergeMonthlyCounts({}, fresh);
+    expect(result).toEqual(fresh);
+  });
+
+  it('does not mutate inputs', () => {
+    const existing = { '2026-01': 5 };
+    const fresh = { '2026-02': 10 };
+    mergeMonthlyCounts(existing, fresh);
+    expect(existing).toEqual({ '2026-01': 5 });
+    expect(fresh).toEqual({ '2026-02': 10 });
+  });
+});

packages/core/src/commands/dashboard-data.ts

@@ -37,10 +37,28 @@ export function buildDashboardStats(digest: DailyDigest, state: Readonly<AgentSt
   };
 }
 
+/**
+ * Merge fresh API counts into existing stored counts.
+ * Months present in the fresh data are updated; months only in the existing data are preserved.
+ * This prevents historical data loss when the API returns incomplete results
+ * (e.g. due to pagination limits or transient failures).
+ */
+export function mergeMonthlyCounts(
+  existing: Record<string, number>,
+  fresh: Record<string, number>,
+): Record<string, number> {
+  const merged = { ...existing };
+  for (const [month, count] of Object.entries(fresh)) {
+    merged[month] = count;
+  }
+  return merged;
+}
+
 /**
  * Persist monthly chart analytics (merged, closed, opened) to state.
  * Each metric is isolated so partial failures don't produce inconsistent state.
- * Skips overwriting when data is empty to avoid wiping chart data on transient API failures.
+ * Fresh API results are merged into existing data so historical months are preserved.
+ * Skips updating when fresh data is empty to avoid wiping chart data on transient API failures.
  */
 export function updateMonthlyAnalytics(
   prs: Array<{ createdAt?: string }>,
@@ -50,17 +68,18 @@ export function updateMonthlyAnalytics(
   openedFromClosed: Record<string, number>,
 ): void {
   const stateManager = getStateManager();
+  const state = stateManager.getState();
 
   try {
     if (Object.keys(monthlyCounts).length > 0) {
-      stateManager.setMonthlyMergedCounts(monthlyCounts);
+      stateManager.setMonthlyMergedCounts(mergeMonthlyCounts(state.monthlyMergedCounts || {}, monthlyCounts));
     }
   } catch (error) {
     warn(MODULE, `Failed to store monthly merged counts: ${errorMessage(error)}`);
   }
   try {
     if (Object.keys(monthlyClosedCounts).length > 0) {
-      stateManager.setMonthlyClosedCounts(monthlyClosedCounts);
+      stateManager.setMonthlyClosedCounts(mergeMonthlyCounts(state.monthlyClosedCounts || {}, monthlyClosedCounts));
     }
   } catch (error) {
     warn(MODULE, `Failed to store monthly closed counts: ${errorMessage(error)}`);
@@ -77,7 +96,7 @@ export function updateMonthlyAnalytics(
       }
     }
     if (Object.keys(combinedOpenedCounts).length > 0) {
-      stateManager.setMonthlyOpenedCounts(combinedOpenedCounts);
+      stateManager.setMonthlyOpenedCounts(mergeMonthlyCounts(state.monthlyOpenedCounts || {}, combinedOpenedCounts));
     }
   } catch (error) {
     warn(MODULE, `Failed to store monthly opened counts: ${errorMessage(error)}`);