fix: fix env line endings (#376)

Author: Chrilleweb

.changeset/eighty-hornets-shop.md

@@ -0,0 +1,5 @@
+---
+'dotenv-diff': patch
+---
+
+fix env handle windows styled line endings

packages/cli/src/core/fixEnv.ts

@@ -50,7 +50,9 @@ export function applyFixes(options: ApplyFixesOptions): {
   if (duplicateKeys.length) {
     const duplicateSet = new Set(duplicateKeys);
 
-    const lines = fs.readFileSync(envPath, 'utf-8').split('\n');
+    const raw = fs.readFileSync(envPath, 'utf-8');
+    const eol = raw.includes('\r\n') ? '\r\n' : '\n';
+    const lines = raw.split(eol);
     const seen = new Set<string>();
     const newLines: string[] = [];
 
@@ -69,18 +71,19 @@ export function applyFixes(options: ApplyFixesOptions): {
       newLines.unshift(line);
     }
 
-    fs.writeFileSync(envPath, newLines.join('\n'));
+    fs.writeFileSync(envPath, newLines.join(eol));
     result.removedDuplicates = duplicateKeys;
   }
 
   // --- Add missing keys to .env ---
   if (missingKeys.length) {
     const content = fs.readFileSync(envPath, 'utf-8');
+    const eol = content.includes('\r\n') ? '\r\n' : '\n';
     const newContent =
       content +
-      (content.endsWith('\n') ? '' : '\n') +
-      missingKeys.map((k) => `${k}=`).join('\n') +
-      '\n';
+      (content.endsWith('\n') ? '' : eol) +
+      missingKeys.map((k) => `${k}=`).join(eol) +
+      eol;
     fs.writeFileSync(envPath, newContent);
     result.addedEnv = missingKeys;
   }

packages/cli/test/unit/core/fixEnv.test.ts

@@ -62,7 +62,7 @@ describe('applyFixes', () => {
 
   it('does not duplicate keys in .env.example if already present', () => {
     fs.writeFileSync(examplePath, 'A=\nB=\n');
-    const { changed, result } = applyFixes({
+    const {} = applyFixes({
       envPath,
       missingKeys: ['B'],
       duplicateKeys: [],
@@ -150,7 +150,7 @@ B=2
     });
 
     const env = fs.readFileSync(envPath, 'utf-8');
-    expect(env).toBe(`A=2\nC=1\nB=2\n`);
+    expect(env).toBe('A=2\nC=1\nB=2\n');
   });
 
   it('handles ensureGitignore=true without throwing (best-effort)', () => {
@@ -164,6 +164,53 @@ B=2
     expect(changed).toBe(false);
   });
 
+  describe('line ending preservation', () => {
+    it('preserves CRLF when removing duplicate keys', () => {
+      fs.writeFileSync(envPath, 'A=1\r\nB=2\r\nA=3\r\n');
+
+      applyFixes({ envPath, missingKeys: [], duplicateKeys: ['A'] });
+
+      const finalContent = fs.readFileSync(envPath, 'utf-8');
+      expect(finalContent).toBe('B=2\r\nA=3\r\n');
+    });
+
+    it('preserves LF when removing duplicate keys', () => {
+      fs.writeFileSync(envPath, 'A=1\nB=2\nA=3\n');
+
+      applyFixes({ envPath, missingKeys: [], duplicateKeys: ['A'] });
+
+      const finalContent = fs.readFileSync(envPath, 'utf-8');
+      expect(finalContent).toBe('B=2\nA=3\n');
+    });
+
+    it('preserves CRLF when adding missing keys', () => {
+      fs.writeFileSync(envPath, 'A=1\r\n');
+
+      applyFixes({ envPath, missingKeys: ['B', 'C'], duplicateKeys: [] });
+
+      const finalContent = fs.readFileSync(envPath, 'utf-8');
+      expect(finalContent).toBe('A=1\r\nB=\r\nC=\r\n');
+    });
+
+    it('preserves LF when adding missing keys', () => {
+      fs.writeFileSync(envPath, 'A=1\n');
+
+      applyFixes({ envPath, missingKeys: ['B', 'C'], duplicateKeys: [] });
+
+      const finalContent = fs.readFileSync(envPath, 'utf-8');
+      expect(finalContent).toBe('A=1\nB=\nC=\n');
+    });
+
+    it('uses CRLF separator when file has no trailing newline and CRLF style', () => {
+      fs.writeFileSync(envPath, 'A=1\r\nB=2'); // no trailing newline
+
+      applyFixes({ envPath, missingKeys: ['C'], duplicateKeys: [] });
+
+      const finalContent = fs.readFileSync(envPath, 'utf-8');
+      expect(finalContent).toBe('A=1\r\nB=2\r\nC=\r\n');
+    });
+  });
+
   describe('ensureGitignore functionality', () => {
     it('creates .gitignore when in git repo but no .gitignore exists', () => {
       const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'dotenv-diff-'));
@@ -230,7 +277,7 @@ B=2
       const gitignorePath = path.join(tmpDir, '.gitignore');
       fs.writeFileSync(gitignorePath, '.env\n.env.*\n');
 
-      const { changed, result } = applyFixes({
+      const { result } = applyFixes({
         envPath,
         missingKeys: [],
         duplicateKeys: [],