feat(cli): support multiple env file argument (#26527)

Closes #26425 

## Overview

This PR adds support for specifying multiple environment files as
arguments when using the Deno CLI. Subsequent files override
pre-existing variables defined in previous files.

If the same variable is defined in the environment and in the file, the
value from the environment takes precedence.

## Example Usage
```bash
deno run --allow-env --env-file --env-file=".env.one" --env-file=".env.two" script.ts
```

---------

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

cli/args/flags.rs

@@ -613,7 +613,7 @@ pub struct Flags {
   pub internal: InternalFlags,
   pub ignore: Vec<String>,
   pub import_map_path: Option<String>,
-  pub env_file: Option<String>,
+  pub env_file: Option<Vec<String>>,
   pub inspect_brk: Option<SocketAddr>,
   pub inspect_wait: Option<SocketAddr>,
   pub inspect: Option<SocketAddr>,
@@ -3775,12 +3775,14 @@ fn env_file_arg() -> Arg {
     .help(cstr!(
       "Load environment variables from local file
   <p(245)>Only the first environment variable with a given key is used.
-  Existing process environment variables are not overwritten.</>"
+  Existing process environment variables are not overwritten, so if variables with the same names already exist in the environment, their values will be preserved.
+  Where multiple declarations for the same environment variable exist in your .env file, the first one encountered is applied. This is determined by the order of the files you pass as arguments.</>"
     ))
     .value_hint(ValueHint::FilePath)
     .default_missing_value(".env")
     .require_equals(true)
     .num_args(0..=1)
+    .action(ArgAction::Append)
 }
 
 fn reload_arg() -> Arg {
@@ -5487,7 +5489,9 @@ fn import_map_arg_parse(flags: &mut Flags, matches: &mut ArgMatches) {
 }
 
 fn env_file_arg_parse(flags: &mut Flags, matches: &mut ArgMatches) {
-  flags.env_file = matches.remove_one::<String>("env-file");
+  flags.env_file = matches
+    .get_many::<String>("env-file")
+    .map(|values| values.cloned().collect());
 }
 
 fn reload_arg_parse(
@@ -7423,7 +7427,7 @@ mod tests {
           allow_all: true,
           ..Default::default()
         },
-        env_file: Some(".example.env".to_owned()),
+        env_file: Some(vec![".example.env".to_owned()]),
         ..Flags::default()
       }
     );
@@ -7517,7 +7521,7 @@ mod tests {
           allow_all: true,
           ..Default::default()
         },
-        env_file: Some(".example.env".to_owned()),
+        env_file: Some(vec![".example.env".to_owned()]),
         unsafely_ignore_certificate_errors: Some(vec![]),
         ..Flags::default()
       }
@@ -8165,7 +8169,7 @@ mod tests {
         subcommand: DenoSubcommand::Run(RunFlags::new_default(
           "script.ts".to_string(),
         )),
-        env_file: Some(".env".to_owned()),
+        env_file: Some(vec![".env".to_owned()]),
         code_cache_enabled: true,
         ..Flags::default()
       }
@@ -8181,7 +8185,7 @@ mod tests {
         subcommand: DenoSubcommand::Run(RunFlags::new_default(
           "script.ts".to_string(),
         )),
-        env_file: Some(".env".to_owned()),
+        env_file: Some(vec![".env".to_owned()]),
         code_cache_enabled: true,
         ..Flags::default()
       }
@@ -8214,7 +8218,7 @@ mod tests {
         subcommand: DenoSubcommand::Run(RunFlags::new_default(
           "script.ts".to_string(),
         )),
-        env_file: Some(".another_env".to_owned()),
+        env_file: Some(vec![".another_env".to_owned()]),
         code_cache_enabled: true,
         ..Flags::default()
       }
@@ -8235,7 +8239,29 @@ mod tests {
         subcommand: DenoSubcommand::Run(RunFlags::new_default(
           "script.ts".to_string(),
         )),
-        env_file: Some(".another_env".to_owned()),
+        env_file: Some(vec![".another_env".to_owned()]),
+        code_cache_enabled: true,
+        ..Flags::default()
+      }
+    );
+  }
+
+  #[test]
+  fn run_multiple_env_file_defined() {
+    let r = flags_from_vec(svec![
+      "deno",
+      "run",
+      "--env-file",
+      "--env-file=.two_env",
+      "script.ts"
+    ]);
+    assert_eq!(
+      r.unwrap(),
+      Flags {
+        subcommand: DenoSubcommand::Run(RunFlags::new_default(
+          "script.ts".to_string(),
+        )),
+        env_file: Some(vec![".env".to_owned(), ".two_env".to_owned()]),
         code_cache_enabled: true,
         ..Flags::default()
       }
@@ -8378,7 +8404,7 @@ mod tests {
           allow_read: Some(vec![]),
           ..Default::default()
         },
-        env_file: Some(".example.env".to_owned()),
+        env_file: Some(vec![".example.env".to_owned()]),
         ..Flags::default()
       }
     );
@@ -10053,7 +10079,7 @@ mod tests {
         unsafely_ignore_certificate_errors: Some(vec![]),
         v8_flags: svec!["--help", "--random-seed=1"],
         seed: Some(1),
-        env_file: Some(".example.env".to_owned()),
+        env_file: Some(vec![".example.env".to_owned()]),
         ..Flags::default()
       }
     );

cli/args/mod.rs

@@ -1128,7 +1128,7 @@ impl CliOptions {
     self.flags.otel_config()
   }
 
-  pub fn env_file_name(&self) -> Option<&String> {
+  pub fn env_file_name(&self) -> Option<&Vec<String>> {
     self.flags.env_file.as_ref()
   }
 
@@ -1935,10 +1935,12 @@ pub fn config_to_deno_graph_workspace_member(
   })
 }
 
-fn load_env_variables_from_env_file(filename: Option<&String>) {
-  let Some(env_file_name) = filename else {
+fn load_env_variables_from_env_file(filename: Option<&Vec<String>>) {
+  let Some(env_file_names) = filename else {
     return;
   };
+
+  for env_file_name in env_file_names.iter().rev() {
     match from_filename(env_file_name) {
       Ok(_) => (),
       Err(error) => {
@@ -1951,6 +1953,7 @@ fn load_env_variables_from_env_file(filename: Option<&String>) {
       }
     }
   }
+}
 
 #[cfg(test)]
 mod test {

cli/standalone/binary.rs

@@ -659,9 +659,15 @@ impl<'a> DenoCompileBinaryWriter<'a> {
     remote_modules_store.add_redirects(&graph.redirects);
 
     let env_vars_from_env_file = match cli_options.env_file_name() {
-      Some(env_filename) => {
+      Some(env_filenames) => {
+        let mut aggregated_env_vars = IndexMap::new();
+        for env_filename in env_filenames.iter().rev() {
           log::info!("{} Environment variables from the file \"{}\" were embedded in the generated executable file", crate::colors::yellow("Warning"), env_filename);
-        get_file_env_vars(env_filename.to_string())?
+
+          let env_vars = get_file_env_vars(env_filename.to_string())?;
+          aggregated_env_vars.extend(env_vars);
+        }
+        aggregated_env_vars
       }
       None => Default::default(),
     };

tests/integration/run_tests.rs

@@ -418,16 +418,6 @@ fn permissions_cache() {
     });
 }
 
-itest!(env_file {
-  args: "run --env=env --allow-env run/env_file.ts",
-  output: "run/env_file.out",
-});
-
-itest!(env_file_missing {
-  args: "run --env=missing --allow-env run/env_file.ts",
-  output: "run/env_file_missing.out",
-});
-
 itest!(lock_write_fetch {
   args:
     "run --quiet --allow-import --allow-read --allow-write --allow-env --allow-run run/lock_write_fetch/main.ts",

tests/specs/run/env_file/__test__.jsonc

@@ -0,0 +1,20 @@
+{
+  "tests": {
+    "basic": {
+      "args": "run --env=./env --allow-env env_file.ts",
+      "output": "env_file.out"
+    },
+    "missing": {
+      "args": "run --env=./missing --allow-env env_file.ts",
+      "output": "env_file_missing.out"
+    },
+    "multiple": {
+      "args": "run --env=./env --env=./env_one --env=./env_two --allow-env env_file.ts",
+      "output": "multiple_env_file.out"
+    },
+    "unparseable": {
+      "args": "run --env=./env_unparseable --allow-env env_file.ts",
+      "output": "env_unparseable.out"
+    }
+  }
+}

tests/specs/run/env_file/env

@@ -0,0 +1,4 @@
+FOO=BAR
+ANOTHER_FOO=ANOTHER_${FOO}
+MULTILINE="First Line
+Second Line"

tests/specs/run/env_file/env_file_missing.out

@@ -1,4 +1,4 @@
-Warning The `--env-file` flag was used, but the environment file specified 'missing' was not found.
+Warning The `--env-file` flag was used, but the environment file specified './missing' was not found.
 undefined
 undefined
 undefined

tests/specs/run/env_file/env_one

@@ -0,0 +1,2 @@
+FOO=BARBAR
+ANOTHER_FOO=OVERRIDEN_BY_ENV_ONE

tests/specs/run/env_file/env_two

@@ -0,0 +1 @@
+FOO=OVERRIDEN_BY_ENV_TWO

tests/specs/run/env_file/env_unparseable.out

@@ -0,0 +1,4 @@
+Warning Parsing failed within the specified environment file: ./env_unparseable at index: 3 of the value: c:\path
+valid
+undefined
+undefined

tests/specs/run/env_file/multiple_env_file.out

@@ -0,0 +1,4 @@
+OVERRIDEN_BY_ENV_TWO
+OVERRIDEN_BY_ENV_ONE
+First Line
+Second Line

tests/specs/run/env_unparsable_file/__test__.jsonc

@@ -1,4 +0,0 @@
-{
-  "args": "run --env=../../../testdata/env_unparsable --allow-env main.js",
-  "output": "main.out"
-}

tests/specs/run/env_unparsable_file/main.js

@@ -1,3 +0,0 @@
-console.log(Deno.env.get("FOO"));
-console.log(Deno.env.get("ANOTHER_FOO"));
-console.log(Deno.env.get("MULTILINE"));

tests/specs/run/env_unparsable_file/main.out

@@ -1,4 +0,0 @@
-Warning Parsing failed within the specified environment file: ../../../testdata/env_unparsable at index: 3 of the value: c:\path
-valid
-undefined
-undefined

tools/lint.js

@@ -219,7 +219,7 @@ async function ensureNoNewITests() {
     "pm_tests.rs": 0,
     "publish_tests.rs": 0,
     "repl_tests.rs": 0,
-    "run_tests.rs": 20,
+    "run_tests.rs": 18,
     "shared_library_tests.rs": 0,
     "task_tests.rs": 2,
     "test_tests.rs": 0,