fix: degrade version PR body when it exceeds GitHub's 65536-char limit

.bumpy/version-pr-body-limit.md

@@ -0,0 +1,5 @@
+---
+'@varlock/bumpy': patch
+---
+
+Degrade the version PR body when it would exceed GitHub's 65536-character limit (which previously failed the release for large multi-package releases). The body now drops inline change summaries — and hard-truncates as a last resort — instead of erroring.

packages/bumpy/src/commands/ci.ts

@@ -1420,7 +1420,14 @@ function sha256Hex(input: string): string {
   return createHash('sha256').update(input).digest('hex');
 }
 
-function formatVersionPrBody(
+// GitHub rejects pull request bodies longer than this many characters
+// (GraphQL: "Body is too long (maximum is 65536 characters)"). We leave a
+// little headroom for safety since GitHub's count and JS string length can
+// differ slightly for multi-byte characters.
+const GH_BODY_MAX = 65_536;
+const GH_BODY_SAFE = 64_000;
+
+export function formatVersionPrBody(
   plan: ReleasePlan,
   preamble: string,
   packageDirs: Map<string, string>,
@@ -1429,63 +1436,90 @@ function formatVersionPrBody(
   showNoPatWarning = false,
 ): string {
   const changesBaseUrl = repo && prNumber ? `https://github.com/${repo}/pull/${prNumber}/changes` : null;
-  const lines: string[] = [];
-  lines.push(preamble);
-  lines.push('');
 
   const groups: Record<string, PlannedRelease[]> = { major: [], minor: [], patch: [] };
   for (const r of plan.releases) {
     groups[r.type]?.push(r);
   }
 
-  for (const type of ['major', 'minor', 'patch'] as const) {
-    const releases = groups[type];
-    if (!releases || releases.length === 0) continue;
-
-    lines.push(bumpSectionHeader(type));
+  // Render the body at a given detail level. `includeSummaries: false` drops
+  // the per-change bullet points, leaving just the version-bump headers — a
+  // big size reduction for releases with many or large change summaries.
+  const render = (includeSummaries: boolean): string => {
+    const lines: string[] = [];
+    lines.push(preamble);
     lines.push('');
-    for (const r of releases) {
-      const suffix = r.isDependencyBump ? ' _(dep)_' : r.isCascadeBump ? ' _(cascade)_' : '';
-      const pkgDir = packageDirs.get(r.name);
-      const diffLinks = pkgDir ? buildDiffLinks(pkgDir, changesBaseUrl) : '';
-      lines.push(`#### \`${r.name}\` ${r.oldVersion} → **${r.newVersion}**${suffix}${diffLinks}`);
+
+    if (!includeSummaries) {
+      lines.push(
+        '> ℹ️ This release contains too many changes to summarize inline. See the **Files changed** tab and each package’s `CHANGELOG.md` for details.',
+      );
       lines.push('');
+    }
+
+    for (const type of ['major', 'minor', 'patch'] as const) {
+      const releases = groups[type];
+      if (!releases || releases.length === 0) continue;
 
-      const relevantBumpFiles = plan.bumpFiles.filter((bf) => r.bumpFiles.includes(bf.id));
-
-      if (relevantBumpFiles.length > 0) {
-        for (const bf of relevantBumpFiles) {
-          if (bf.summary) {
-            const bfLink = changesBaseUrl
-              ? ` ([bump file](${changesBaseUrl}#diff-${sha256Hex(`.bumpy/${bf.id}.md`)}))`
-              : '';
-            const summaryLines = bf.summary.split('\n');
-            lines.push(`- ${summaryLines[0]}${bfLink}`);
-            for (let i = 1; i < summaryLines.length; i++) {
-              if (summaryLines[i]!.trim()) {
-                lines.push(`  ${summaryLines[i]}`);
+      lines.push(bumpSectionHeader(type));
+      lines.push('');
+      for (const r of releases) {
+        const suffix = r.isDependencyBump ? ' _(dep)_' : r.isCascadeBump ? ' _(cascade)_' : '';
+        const pkgDir = packageDirs.get(r.name);
+        const diffLinks = pkgDir ? buildDiffLinks(pkgDir, changesBaseUrl) : '';
+        lines.push(`#### \`${r.name}\` ${r.oldVersion} → **${r.newVersion}**${suffix}${diffLinks}`);
+        lines.push('');
+
+        if (!includeSummaries) continue;
+
+        const relevantBumpFiles = plan.bumpFiles.filter((bf) => r.bumpFiles.includes(bf.id));
+
+        if (relevantBumpFiles.length > 0) {
+          for (const bf of relevantBumpFiles) {
+            if (bf.summary) {
+              const bfLink = changesBaseUrl
+                ? ` ([bump file](${changesBaseUrl}#diff-${sha256Hex(`.bumpy/${bf.id}.md`)}))`
+                : '';
+              const summaryLines = bf.summary.split('\n');
+              lines.push(`- ${summaryLines[0]}${bfLink}`);
+              for (let i = 1; i < summaryLines.length; i++) {
+                if (summaryLines[i]!.trim()) {
+                  lines.push(`  ${summaryLines[i]}`);
+                }
               }
             }
           }
+        } else if (r.isDependencyBump) {
+          lines.push('- Updated dependencies');
+        } else if (r.isCascadeBump) {
+          lines.push('- Version bump via cascade rule');
         }
-      } else if (r.isDependencyBump) {
-        lines.push('- Updated dependencies');
-      } else if (r.isCascadeBump) {
-        lines.push('- Version bump via cascade rule');
+
+        lines.push('');
       }
+    }
 
+    if (showNoPatWarning) {
+      lines.push(
+        '> ⚠️ `BUMPY_GH_TOKEN` is not set — CI checks will not run automatically on this PR. Run `bumpy ci setup` for help.',
+      );
       lines.push('');
     }
-  }
 
-  if (showNoPatWarning) {
-    lines.push(
-      '> ⚠️ `BUMPY_GH_TOKEN` is not set — CI checks will not run automatically on this PR. Run `bumpy ci setup` for help.',
-    );
-    lines.push('');
-  }
+    return lines.join('\n');
+  };
 
-  return lines.join('\n');
+  const full = render(true);
+  if (full.length <= GH_BODY_SAFE) return full;
+
+  // Too long for GitHub — drop the inline change summaries and keep just the
+  // version-bump list. This is rare (dozens of packages or huge changelogs).
+  const compact = render(false);
+  if (compact.length <= GH_BODY_SAFE) return compact;
+
+  // Still too long (an enormous number of packages) — hard-truncate.
+  const notice = '\n\n> ⚠️ This release list was truncated because it exceeds GitHub’s size limit.';
+  return compact.slice(0, GH_BODY_MAX - notice.length) + notice;
 }
 
 const COMMENT_MARKER = '<!-- bumpy-release-plan -->';

packages/bumpy/test/core/ci-version-pr-body.test.ts

@@ -0,0 +1,69 @@
+import { describe, test, expect } from 'bun:test';
+import { formatVersionPrBody } from '../../src/commands/ci.ts';
+import type { ReleasePlan, PlannedRelease, BumpFile } from '../../src/types.ts';
+
+// GitHub rejects PR bodies longer than 65536 characters. bumpy should degrade
+// gracefully rather than fail the release when there are many packages and/or
+// huge change summaries.
+const GH_LIMIT = 65_536;
+
+function makePlan(count: number, summary: string): ReleasePlan {
+  const releases: PlannedRelease[] = [];
+  const bumpFiles: BumpFile[] = [];
+  for (let i = 0; i < count; i++) {
+    const id = `bump-${i}`;
+    bumpFiles.push({ id, releases: [{ name: `@scope/pkg-${i}`, type: 'minor' }], summary });
+    releases.push({
+      name: `@scope/pkg-${i}`,
+      type: 'minor',
+      oldVersion: '1.0.0',
+      newVersion: '1.1.0',
+      bumpFiles: [id],
+      isDependencyBump: false,
+      isCascadeBump: false,
+      isGroupBump: false,
+      bumpSources: [],
+    });
+  }
+  return { bumpFiles, releases, warnings: [] };
+}
+
+const packageDirs = new Map<string, string>();
+for (let i = 0; i < 200; i++) packageDirs.set(`@scope/pkg-${i}`, `packages/pkg-${i}`);
+
+describe('formatVersionPrBody — within size limit', () => {
+  const body = formatVersionPrBody(makePlan(3, 'Add a feature'), 'Release', packageDirs, 'owner/repo', '42');
+
+  test('includes inline change summaries', () => {
+    expect(body).toContain('Add a feature');
+    expect(body).toContain('@scope/pkg-0');
+    expect(body.length).toBeLessThanOrEqual(GH_LIMIT);
+  });
+});
+
+describe('formatVersionPrBody — exceeds limit via large summaries', () => {
+  // 30 packages each with a multi-KB summary blows past 65536 chars.
+  const bigSummary = 'Detailed change notes. '.repeat(150);
+  const body = formatVersionPrBody(makePlan(30, bigSummary), 'Release', packageDirs, 'owner/repo', '42');
+
+  test('stays under the GitHub limit', () => {
+    expect(body.length).toBeLessThanOrEqual(GH_LIMIT);
+  });
+
+  test('drops the inline summaries but keeps the version-bump list', () => {
+    expect(body).not.toContain('Detailed change notes.');
+    expect(body).toContain('@scope/pkg-0');
+    expect(body).toContain('@scope/pkg-29');
+    expect(body).toContain('too many changes to summarize');
+  });
+});
+
+describe('formatVersionPrBody — exceeds limit even compact', () => {
+  // Thousands of packages: even the header-only list overflows.
+  const body = formatVersionPrBody(makePlan(3000, 'x'), 'Release', packageDirs, 'owner/repo', '42');
+
+  test('hard-truncates to under the GitHub limit', () => {
+    expect(body.length).toBeLessThanOrEqual(GH_LIMIT);
+    expect(body).toContain('truncated');
+  });
+});