src: add built-in .env file support

doc/api/cli.md

@@ -984,6 +984,41 @@ surface on other platforms, but the performance impact may be severe.
 This flag is inherited from V8 and is subject to change upstream. It may
 disappear in a non-semver-major release.
 
+### `--env-file=config`
+
+> Stability: 1.1 - Active development
+
+<!-- YAML
+added: REPLACEME
+-->
+
+Loads environment variables from a file relative to the current directory,
+making them available to applications on `process.env`. The [environment
+variables which configure Node.js][environment_variables], such as `NODE_OPTIONS`,
+are parsed and applied. If the same variable is defined in the environment and
+in the file, the value from the environment takes precedence.
+
+The format of the file should be one line per key-value pair of environment
+variable name and value separated by `=`:
+
+```text
+PORT=3000
+```
+
+Any text after a `#` is treated as a comment:
+
+```text
+# This is a comment
+PORT=3000 # This is also a comment
+```
+
+Values can start and end with the following quotes: `\`, `"` or `'`.
+They are omitted from the values.
+
+```text
+USERNAME="nodejs" # will result in `nodejs` as the value.
+```
+
 ### `--max-http-header-size=size`
 
 <!-- YAML
@@ -2647,6 +2682,7 @@ done
 [debugger]: debugger.md
 [debugging security implications]: https://nodejs.org/en/docs/guides/debugging-getting-started/#security-implications
 [emit_warning]: process.md#processemitwarningwarning-options
+[environment_variables]: #environment-variables
 [filtering tests by name]: test.md#filtering-tests-by-name
 [jitless]: https://v8.dev/blog/jitless
 [libuv threadpool documentation]: https://docs.libuv.org/en/latest/threadpool.html

node.gyp

@@ -100,6 +100,7 @@
       'src/node_contextify.cc',
       'src/node_credentials.cc',
       'src/node_dir.cc',
+      'src/node_dotenv.cc',
       'src/node_env_var.cc',
       'src/node_errors.cc',
       'src/node_external_reference.cc',
@@ -214,6 +215,7 @@
       'src/node_context_data.h',
       'src/node_contextify.h',
       'src/node_dir.h',
+      'src/node_dotenv.h',
       'src/node_errors.h',
       'src/node_exit_code.h',
       'src/node_external_reference.h',

src/env.cc

@@ -683,7 +683,7 @@ void Environment::TryLoadAddon(
   }
 }
 
-std::string Environment::GetCwd() {
+std::string Environment::GetCwd(const std::string& exec_path) {
   char cwd[PATH_MAX_BYTES];
   size_t size = PATH_MAX_BYTES;
   const int err = uv_cwd(cwd, &size);
@@ -695,7 +695,6 @@ std::string Environment::GetCwd() {
 
   // This can fail if the cwd is deleted. In that case, fall back to
   // exec_path.
-  const std::string& exec_path = exec_path_;
   return exec_path.substr(0, exec_path.find_last_of(kPathSeparator));
 }
 
@@ -729,7 +728,7 @@ std::unique_ptr<v8::BackingStore> Environment::release_managed_buffer(
   return bs;
 }
 
-std::string GetExecPath(const std::vector<std::string>& argv) {
+std::string Environment::GetExecPath(const std::vector<std::string>& argv) {
   char exec_path_buf[2 * PATH_MAX];
   size_t exec_path_len = sizeof(exec_path_buf);
   std::string exec_path;
@@ -771,7 +770,7 @@ Environment::Environment(IsolateData* isolate_data,
       timer_base_(uv_now(isolate_data->event_loop())),
       exec_argv_(exec_args),
       argv_(args),
-      exec_path_(GetExecPath(args)),
+      exec_path_(Environment::GetExecPath(args)),
       exit_info_(
           isolate_, kExitInfoFieldCount, MAYBE_FIELD_PTR(env_info, exit_info)),
       should_abort_on_uncaught_toggle_(
@@ -1921,7 +1920,7 @@ size_t Environment::NearHeapLimitCallback(void* data,
 
   std::string dir = env->options()->diagnostic_dir;
   if (dir.empty()) {
-    dir = env->GetCwd();
+    dir = Environment::GetCwd(env->exec_path_);
   }
   DiagnosticFilename name(env, "Heap", "heapsnapshot");
   std::string filename = dir + kPathSeparator + (*name);

src/env.h

@@ -588,6 +588,9 @@ class Environment : public MemoryRetainer {
 
   SET_MEMORY_INFO_NAME(Environment)
 
+  static std::string GetExecPath(const std::vector<std::string>& argv);
+  static std::string GetCwd(const std::string& exec_path);
+
   inline size_t SelfSize() const override;
   bool IsRootNode() const override { return true; }
   void MemoryInfo(MemoryTracker* tracker) const override;
@@ -604,8 +607,6 @@ class Environment : public MemoryRetainer {
   // Should be called before InitializeInspector()
   void InitializeDiagnostics();
 
-  std::string GetCwd();
-
 #if HAVE_INSPECTOR
   // If the environment is created for a worker, pass parent_handle and
   // the ownership if transferred into the Environment.

src/heap_utils.cc

@@ -456,7 +456,9 @@ void TriggerHeapSnapshot(const FunctionCallbackInfo<Value>& args) {
   if (filename_v->IsUndefined()) {
     DiagnosticFilename name(env, "Heap", "heapsnapshot");
     THROW_IF_INSUFFICIENT_PERMISSIONS(
-        env, permission::PermissionScope::kFileSystemWrite, env->GetCwd());
+        env,
+        permission::PermissionScope::kFileSystemWrite,
+        Environment::GetCwd(env->exec_path()));
     if (WriteSnapshot(env, *name, options).IsNothing()) return;
     if (String::NewFromUtf8(isolate, *name).ToLocal(&filename_v)) {
       args.GetReturnValue().Set(filename_v);

src/inspector_profiler.cc

@@ -431,7 +431,8 @@ void StartProfilers(Environment* env) {
   if (env->options()->cpu_prof) {
     const std::string& dir = env->options()->cpu_prof_dir;
     env->set_cpu_prof_interval(env->options()->cpu_prof_interval);
-    env->set_cpu_prof_dir(dir.empty() ? env->GetCwd() : dir);
+    env->set_cpu_prof_dir(dir.empty() ? Environment::GetCwd(env->exec_path())
+                                      : dir);
     if (env->options()->cpu_prof_name.empty()) {
       DiagnosticFilename filename(env, "CPU", "cpuprofile");
       env->set_cpu_prof_name(*filename);
@@ -446,7 +447,8 @@ void StartProfilers(Environment* env) {
   if (env->options()->heap_prof) {
     const std::string& dir = env->options()->heap_prof_dir;
     env->set_heap_prof_interval(env->options()->heap_prof_interval);
-    env->set_heap_prof_dir(dir.empty() ? env->GetCwd() : dir);
+    env->set_heap_prof_dir(dir.empty() ? Environment::GetCwd(env->exec_path())
+                                       : dir);
     if (env->options()->heap_prof_name.empty()) {
       DiagnosticFilename filename(env, "Heap", "heapprofile");
       env->set_heap_prof_name(*filename);

src/node.cc

@@ -20,6 +20,7 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 #include "node.h"
+#include "node_dotenv.h"
 
 // ========== local headers ==========
 
@@ -140,6 +141,10 @@ using v8::Value;
 
 namespace per_process {
 
+// node_dotenv.h
+// Instance is used to store environment variables including NODE_OPTIONS.
+node::Dotenv dotenv_file = Dotenv();
+
 // node_revert.h
 // Bit flag used to track security reverts.
 unsigned int reverted_cve = 0;
@@ -305,6 +310,10 @@ MaybeLocal<Value> StartExecution(Environment* env, StartExecutionCallback cb) {
   }
 #endif
 
+  if (env->options()->has_env_file_string) {
+    per_process::dotenv_file.SetEnvironment(env);
+  }
+
   // TODO(joyeecheung): move these conditions into JS land and let the
   // deserialize main function take precedence. For workers, we need to
   // move the pre-execution part into a different file that can be
@@ -831,11 +840,22 @@ static ExitCode InitializeNodeWithArgsInternal(
 
   HandleEnvOptions(per_process::cli_options->per_isolate->per_env);
 
+  std::string node_options;
+  auto file_path = node::Dotenv::GetPathFromArgs(*argv);
+
+  if (file_path.has_value()) {
+    auto cwd = Environment::GetCwd(Environment::GetExecPath(*argv));
+    std::string path = cwd + kPathSeparator + file_path.value();
+    CHECK(!per_process::v8_initialized);
+    per_process::dotenv_file.ParsePath(path);
+    per_process::dotenv_file.AssignNodeOptionsIfAvailable(&node_options);
+  }
+
 #if !defined(NODE_WITHOUT_NODE_OPTIONS)
   if (!(flags & ProcessInitializationFlags::kDisableNodeOptionsEnv)) {
-    std::string node_options;
-
-    if (credentials::SafeGetenv("NODE_OPTIONS", &node_options)) {
+    // NODE_OPTIONS environment variable is preferred over the file one.
+    if (credentials::SafeGetenv("NODE_OPTIONS", &node_options) ||
+        !node_options.empty()) {
       std::vector<std::string> env_argv =
           ParseNodeOptionsEnvVar(node_options, errors);
 

src/node_credentials.cc

@@ -123,7 +123,6 @@ bool SafeGetenv(const char* key,
   }
 
 fail:
-  text->clear();
   return false;
 }
 

src/node_dotenv.cc

@@ -0,0 +1,164 @@
+#include "node_dotenv.h"
+#include "env-inl.h"
+#include "node_file.h"
+#include "uv.h"
+
+namespace node {
+
+using v8::NewStringType;
+using v8::String;
+
+std::optional<std::string> Dotenv::GetPathFromArgs(
+    const std::vector<std::string>& args) {
+  std::string_view flag = "--env-file";
+  // Match the last `--env-file`
+  // This is required to imitate the default behavior of Node.js CLI argument
+  // matching.
+  auto path =
+      std::find_if(args.rbegin(), args.rend(), [&flag](const std::string& arg) {
+        return strncmp(arg.c_str(), flag.data(), flag.size()) == 0;
+      });
+
+  if (path == args.rend()) {
+    return std::nullopt;
+  }
+
+  auto equal_char = path->find('=');
+
+  if (equal_char != std::string::npos) {
+    return path->substr(equal_char + 1);
+  }
+
+  auto next_arg = std::prev(path);
+
+  if (next_arg == args.rend()) {
+    return std::nullopt;
+  }
+
+  return *next_arg;
+}
+
+void Dotenv::SetEnvironment(node::Environment* env) {
+  if (store_.empty()) {
+    return;
+  }
+
+  auto isolate = env->isolate();
+
+  for (const auto& entry : store_) {
+    auto key = entry.first;
+    auto value = entry.second;
+    env->env_vars()->Set(
+        isolate,
+        v8::String::NewFromUtf8(
+            isolate, key.data(), NewStringType::kNormal, key.size())
+            .ToLocalChecked(),
+        v8::String::NewFromUtf8(
+            isolate, value.data(), NewStringType::kNormal, value.size())
+            .ToLocalChecked());
+  }
+}
+
+void Dotenv::ParsePath(const std::string_view path) {
+  uv_fs_t req;
+  auto defer_req_cleanup = OnScopeLeave([&req]() { uv_fs_req_cleanup(&req); });
+
+  uv_file file = uv_fs_open(nullptr, &req, path.data(), 0, 438, nullptr);
+  if (req.result < 0) {
+    // req will be cleaned up by scope leave.
+    return;
+  }
+  uv_fs_req_cleanup(&req);
+
+  auto defer_close = OnScopeLeave([file]() {
+    uv_fs_t close_req;
+    CHECK_EQ(0, uv_fs_close(nullptr, &close_req, file, nullptr));
+    uv_fs_req_cleanup(&close_req);
+  });
+
+  std::string result{};
+  char buffer[8192];
+  uv_buf_t buf = uv_buf_init(buffer, sizeof(buffer));
+
+  while (true) {
+    auto r = uv_fs_read(nullptr, &req, file, &buf, 1, -1, nullptr);
+    if (req.result < 0) {
+      // req will be cleaned up by scope leave.
+      return;
+    }
+    uv_fs_req_cleanup(&req);
+    if (r <= 0) {
+      break;
+    }
+    result.append(buf.base, r);
+  }
+
+  using std::string_view_literals::operator""sv;
+  auto lines = SplitString(result, "\n"sv);
+
+  for (const auto& line : lines) {
+    ParseLine(line);
+  }
+}
+
+void Dotenv::AssignNodeOptionsIfAvailable(std::string* node_options) {
+  auto match = store_.find("NODE_OPTIONS");
+
+  if (match != store_.end()) {
+    *node_options = match->second;
+  }
+}
+
+void Dotenv::ParseLine(const std::string_view line) {
+  auto equal_index = line.find('=');
+
+  if (equal_index == std::string_view::npos) {
+    return;
+  }
+
+  auto key = line.substr(0, equal_index);
+
+  // Remove leading and trailing space characters from key.
+  while (!key.empty() && std::isspace(key.front())) key.remove_prefix(1);
+  while (!key.empty() && std::isspace(key.back())) key.remove_suffix(1);
+
+  // Omit lines with comments
+  if (key.front() == '#' || key.empty()) {
+    return;
+  }
+
+  auto value = std::string(line.substr(equal_index + 1));
+
+  // Might start and end with `"' characters.
+  auto quotation_index = value.find_first_of("`\"'");
+
+  if (quotation_index == 0) {
+    auto quote_character = value[quotation_index];
+    value.erase(0, 1);
+
+    auto end_quotation_index = value.find_last_of(quote_character);
+
+    // We couldn't find the closing quotation character. Terminate.
+    if (end_quotation_index == std::string::npos) {
+      return;
+    }
+
+    value.erase(end_quotation_index);
+  } else {
+    auto hash_index = value.find('#');
+
+    // Remove any inline comments
+    if (hash_index != std::string::npos) {
+      value.erase(hash_index);
+    }
+
+    // Remove any leading/trailing spaces from unquoted values.
+    while (!value.empty() && std::isspace(value.front())) value.erase(0, 1);
+    while (!value.empty() && std::isspace(value.back()))
+      value.erase(value.size() - 1);
+  }
+
+  store_.emplace(key, value);
+}
+
+}  // namespace node