fix(#1224): accept --pr 0 placeholder at changeset creation (#1231)

* fix(#1224): accept --pr 0 placeholder at changeset creation

The required-field guard `!opts.pr` treated the integer 0 as falsy,
rejecting the documented `pr: 0` two-push placeholder with a usage
error (exit 2). Non-numeric `--pr abc` (NaN) was also silently
accepted before (passes `!NaN === true`... actually `!NaN` is true, so
NaN would trigger the guard already). The new explicit checks use
`opts.pr === null` for missing flag and `Number.isNaN` for non-numeric
input, accepting all finite integer values including 0.

The merge-time safety net in parse.cjs (`pr <= 0` → INVALID_PR) is
unchanged — a pr:0 fragment is still rejected at lint/render time.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* chore(#1224): backfill changeset PR number (#1231)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

tests/changeset-new.test.cjs

@@ -6,15 +6,19 @@ const assert = require('node:assert/strict');
 const fs = require('node:fs');
 const os = require('node:os');
 const path = require('node:path');
+const { spawnSync } = require('node:child_process');
 
 const ROOT = path.join(__dirname, '..');
-const { generateFragmentName, scaffoldFragment, parseFragment } = (() => {
+const { generateFragmentName, scaffoldFragment, parseFragment, parseArgs } = (() => {
   const newCs = require(path.join(ROOT, 'scripts', 'changeset', 'new.cjs'));
   const parse = require(path.join(ROOT, 'scripts', 'changeset', 'parse.cjs'));
   return { ...newCs, parseFragment: parse.parseFragment };
 })();
+const { FRAGMENT_ERROR } = require(path.join(ROOT, 'scripts', 'changeset', 'parse.cjs'));
 const { cleanup } = require('./helpers.cjs');
 
+const NEW_CJS = path.join(ROOT, 'scripts', 'changeset', 'new.cjs');
+
 let tmp;
 before(() => { tmp = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-new-changeset-')); });
 after(() => { cleanup(tmp); });
@@ -95,3 +99,85 @@ describe('changeset new: name generator + scaffold writer (#2975)', () => {
     assert.deepEqual(r.opts, { type: 'Fixed', pr: 42, body: 'a body', repo: '/tmp/x' });
   });
 });
+
+describe('changeset new: --pr 0 placeholder acceptance (bug #1224)', () => {
+  // (a) The headline bug: `main()` (not just parseArgs) must ACCEPT --pr 0.
+  //     We exercise the end-to-end CLI path via spawnSync so that main()'s guard
+  //     is on the critical path. Old code had `if (!opts.pr)` which treated 0 as
+  //     falsy and exited with code 2. Fixed code uses explicit `=== null` / isNaN
+  //     guards and must exit 0 and write a fragment file with pr: 0 in frontmatter.
+  test('(a) CLI main() accepts --pr 0 (exit 0) and writes a pr:0 fragment rejected at lint time', () => {
+    // Use an isolated temp dir per invocation to avoid .changeset/ pollution
+    // from other tests sharing `tmp`.
+    const isolatedDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-new-cs-a-'));
+    try {
+      const result = spawnSync(
+        process.execPath,
+        [NEW_CJS, '--type', 'Fixed', '--pr', '0', '--body', 'placeholder for pr-zero.', '--repo', isolatedDir],
+        { encoding: 'utf8', timeout: 10000 },
+      );
+
+      // The bug: old main() did `if (!opts.pr)` → exit 2. Fixed: exit 0.
+      assert.equal(result.status, 0,
+        `CLI main() must exit 0 for --pr 0; got status=${result.status} stderr=${result.stderr}`);
+
+      // A fragment file must exist under .changeset/
+      const csDir = path.join(isolatedDir, '.changeset');
+      const files = fs.readdirSync(csDir).filter(f => f.endsWith('.md'));
+      assert.equal(files.length, 1,
+        `Expected exactly one fragment file in ${csDir}, got: ${JSON.stringify(files)}`);
+
+      // The written fragment must round-trip through parseFragment as INVALID_PR,
+      // confirming pr:0 was embedded (not absent, NaN, or a positive integer).
+      const src = fs.readFileSync(path.join(csDir, files[0]), 'utf8');
+      const parsed = parseFragment(src);
+      assert.equal(parsed.ok, false, 'parseFragment must reject a pr:0 fragment at lint time');
+      assert.equal(parsed.reason, FRAGMENT_ERROR.INVALID_PR,
+        `expected INVALID_PR, got: ${parsed.reason}`);
+    } finally {
+      cleanup(isolatedDir);
+    }
+  });
+
+  // (b) missing --pr: parseArgs leaves opts.pr as null, causing main() to reject.
+  test('(b) missing --pr leaves opts.pr as null (rejected by main validation)', () => {
+    const r = parseArgs(['--type', 'Fixed', '--body', 'body without pr flag.', '--repo', tmp]);
+    assert.equal(r.ok, true, 'parseArgs itself succeeds; rejection is in main()');
+    assert.equal(r.opts.pr, null, `opts.pr should be null when --pr is omitted, got: ${r.opts.pr}`);
+    // prMissing = opts.pr === null → would trigger rejection in main()
+    assert.equal(r.opts.pr === null, true, 'prMissing condition must be true');
+  });
+
+  // (c) --pr abc: non-numeric input normalised to NaN by parseArgs.
+  test('(c) --pr abc (non-numeric) produces NaN in opts.pr (rejected by main validation)', () => {
+    const r = parseArgs(['--type', 'Fixed', '--pr', 'abc', '--body', 'body.', '--repo', tmp]);
+    assert.equal(r.ok, true, 'parseArgs itself succeeds; rejection is in main()');
+    assert.equal(Number.isNaN(r.opts.pr), true,
+      `opts.pr should be NaN for non-numeric input, got: ${r.opts.pr}`);
+  });
+
+  // (d1) --pr "" (empty string): trimmed to "", /^\d+$/ fails → NaN.
+  test('(d1) --pr "" (empty string) produces NaN in opts.pr (rejected by main validation)', () => {
+    const r = parseArgs(['--type', 'Fixed', '--pr', '', '--body', 'body.', '--repo', tmp]);
+    assert.equal(r.ok, true, 'parseArgs itself succeeds; rejection is in main()');
+    assert.equal(Number.isNaN(r.opts.pr), true,
+      `opts.pr should be NaN for empty string, got: ${r.opts.pr}`);
+  });
+
+  // (d2) --pr "   " (whitespace-only): trimmed to "", /^\d+$/ fails → NaN.
+  test('(d2) --pr "   " (whitespace-only) produces NaN in opts.pr (rejected by main validation)', () => {
+    const r = parseArgs(['--type', 'Fixed', '--pr', '   ', '--body', 'body.', '--repo', tmp]);
+    assert.equal(r.ok, true, 'parseArgs itself succeeds; rejection is in main()');
+    assert.equal(Number.isNaN(r.opts.pr), true,
+      `opts.pr should be NaN for whitespace-only input, got: ${r.opts.pr}`);
+  });
+
+  // (e) parse.cjs rejects a pr:0 fragment — the merge-time lint safety net is intact.
+  test('(e) parseFragment rejects a pr:0 fragment with INVALID_PR (lint safety net intact)', () => {
+    const fragmentContent = `---\ntype: Fixed\npr: 0\n---\nsome body text.\n`;
+    const result = parseFragment(fragmentContent);
+    assert.equal(result.ok, false, 'parseFragment must reject pr:0 at lint time');
+    assert.equal(result.reason, FRAGMENT_ERROR.INVALID_PR,
+      `expected INVALID_PR reason, got: ${result.reason}`);
+  });
+});