Repository: nodejs/node
Pull request: src: improve node::Dotenv trimming

the trimming functionality that the dotenv parsing uses currently only takes into consideration plain spaces (' '), other type of space characters such as tabs and newlines are not trimmed, this can cause subtle bugs, so the changes here make sure that such characters get trimmed as well

Fixes #56686 

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Changed files:
filename: src/node_dotenv.cc
patch: @@ -105,15 +105,22 @@ Local<Object> Dotenv::ToObject(Environment* env) const {
   return result;
 }
 
+// Removes space characters (spaces, tabs and newlines) from
+// the start and end of a given input string
 std::string_view trim_spaces(std::string_view input) {
   if (input.empty()) return "";
-  if (input.front() == ' ') {
-    input.remove_prefix(input.find_first_not_of(' '));
+
+  auto pos_start = input.find_first_not_of(" \t\n");
+  if (pos_start == std::string_view::npos) {
+    return "";
   }
-  if (!input.empty() && input.back() == ' ') {
-    input = input.substr(0, input.find_last_not_of(' ') + 1);
+
+  auto pos_end = input.find_last_not_of(" \t\n");
+  if (pos_end == std::string_view::npos) {
+    return input.substr(pos_start);
   }
-  return input;
+
+  return input.substr(pos_start, pos_end - pos_start + 1);
 }
 
 void Dotenv::ParseContent(const std::string_view input) {
@@ -147,6 +154,13 @@ void Dotenv::ParseContent(const std::string_view input) {
     key = content.substr(0, equal);
     content.remove_prefix(equal + 1);
     key = trim_spaces(key);
+
+    // If the value is not present (e.g. KEY=) set is to an empty string
+    if (content.front() == '\n') {
+      store_.insert_or_assign(std::string(key), "");
+      continue;
+    }
+
     content = trim_spaces(content);
 
     if (key.empty()) {

filename: test/fixtures/dotenv/lines-with-only-spaces.env
patch: @@ -0,0 +1,8 @@
+
+EMPTY_LINE='value after an empty line'
+      
+SPACES_LINE='value after a line with just some spaces'
+				
+TABS_LINE='value after a line with just some tabs'
+	    			
+SPACES_TABS_LINE='value after a line with just some spaces and tabs'

filename: test/parallel/test-dotenv-edge-cases.js
patch: @@ -137,6 +137,25 @@ describe('.env supports edge cases', () => {
     assert.strictEqual(child.code, 0);
   });
 
+  it('should handle lines that come after lines with only spaces (and tabs)', async () => {
+    // Ref: https://github.com/nodejs/node/issues/56686
+    const code = `
+      process.loadEnvFile('./lines-with-only-spaces.env');
+      assert.strictEqual(process.env.EMPTY_LINE, 'value after an empty line');
+      assert.strictEqual(process.env.SPACES_LINE, 'value after a line with just some spaces');
+      assert.strictEqual(process.env.TABS_LINE, 'value after a line with just some tabs');
+      assert.strictEqual(process.env.SPACES_TABS_LINE, 'value after a line with just some spaces and tabs');
+    `.trim();
+    const child = await common.spawnPromisified(
+      process.execPath,
+      [ '--eval', code ],
+      { cwd: fixtures.path('dotenv') },
+    );
+    assert.strictEqual(child.stdout, '');
+    assert.strictEqual(child.stderr, '');
+    assert.strictEqual(child.code, 0);
+  });
+
   it('should handle when --env-file is passed along with --', async () => {
     const child = await common.spawnPromisified(
       process.execPath,