refactor(migrator): simplify parseNvmrcVersion function and improve alias handling

Author: naokihaba

packages/cli/src/migration/__tests__/migrator.spec.ts

@@ -133,37 +133,36 @@ describe('rewritePackageJson', () => {
 
 describe('parseNvmrcVersion', () => {
   it('strips v prefix', () => {
-    expect(parseNvmrcVersion('v20.5.0\n')).toBe('20.5.0');
     expect(parseNvmrcVersion('v20.5.0')).toBe('20.5.0');
   });
 
   it('passes through version without prefix', () => {
-    expect(parseNvmrcVersion('20.5.0\n')).toBe('20.5.0');
-    expect(parseNvmrcVersion('20\n')).toBe('20');
+    expect(parseNvmrcVersion('20.5.0')).toBe('20.5.0');
+    expect(parseNvmrcVersion('20')).toBe('20');
   });
 
   it('passes through lts aliases', () => {
-    expect(parseNvmrcVersion('lts/*\n')).toBe('lts/*');
-    expect(parseNvmrcVersion('lts/iron\n')).toBe('lts/iron');
-    expect(parseNvmrcVersion('lts/-1\n')).toBe('lts/-1');
+    expect(parseNvmrcVersion('lts/*')).toBe('lts/*');
+    expect(parseNvmrcVersion('lts/iron')).toBe('lts/iron');
+    expect(parseNvmrcVersion('lts/-1')).toBe('lts/-1');
   });
 
   it('converts node/stable aliases to lts/*', () => {
-    expect(parseNvmrcVersion('node\n')).toBe('lts/*');
-    expect(parseNvmrcVersion('stable\n')).toBe('lts/*');
+    expect(parseNvmrcVersion('node')).toBe('lts/*');
+    expect(parseNvmrcVersion('stable')).toBe('lts/*');
   });
 
   it('returns null for untranslatable aliases', () => {
-    expect(parseNvmrcVersion('iojs\n')).toBeNull();
-    expect(parseNvmrcVersion('system\n')).toBeNull();
-    expect(parseNvmrcVersion('default\n')).toBeNull();
+    expect(parseNvmrcVersion('iojs')).toBeNull();
+    expect(parseNvmrcVersion('system')).toBeNull();
+    expect(parseNvmrcVersion('default')).toBeNull();
     expect(parseNvmrcVersion('')).toBeNull();
   });
 
   it('returns null for invalid version strings', () => {
-    expect(parseNvmrcVersion('v\n')).toBeNull();
-    expect(parseNvmrcVersion('laetst\n')).toBeNull();
-    expect(parseNvmrcVersion('20.5.0.1\n')).toBeNull();
+    expect(parseNvmrcVersion('v')).toBeNull();
+    expect(parseNvmrcVersion('laetst')).toBeNull();
+    expect(parseNvmrcVersion('20.5.0.1')).toBeNull();
   });
 });
 

packages/cli/src/migration/migrator.ts

@@ -2002,11 +2002,12 @@ export function detectNodeVersionManagerFile(
 }
 
 /**
- * Parse a version string from a .nvmrc file.
- * Returns null for unsupported aliases like "node", "stable", "system".
+ * Parse a version alias from a .nvmrc file into a .node-version compatible string.
+ * Accepts the first line of .nvmrc (pre-trimmed).
+ * Returns null for unsupported aliases like "system", "default", "iojs".
  */
-export function parseNvmrcVersion(content: string): string | null {
-  const version = content.split('\n')[0]?.trim();
+export function parseNvmrcVersion(alias: string): string | null {
+  const version = alias.trim();
 
   if (!version) {
     return null;
@@ -2049,8 +2050,8 @@ export function migrateNodeVersionManagerFile(
   const sourcePath = path.join(projectPath, '.nvmrc');
   const nodeVersionPath = path.join(projectPath, '.node-version');
   const content = fs.readFileSync(sourcePath, 'utf8');
-  const originalAlias = content.split('\n')[0]?.trim();
-  const version = parseNvmrcVersion(content);
+  const originalAlias = content.split('\n')[0]?.trim() ?? '';
+  const version = parseNvmrcVersion(originalAlias);
 
   if (!version) {
     warnMigration(