feat(unstable): `--unstable-detect-cjs` for respecting explicit `"type": "commonjs"` (#26149)

When using the `--unstable-detect-cjs` flag or adding `"unstable":
["detect-cjs"]` to a deno.json, it will make a JS file CJS if the
closest package.json contains `"type": "commonjs"` and the file is not
an ESM module (no TLA, no `import.meta`, no `import`/`export`).

1 files changed, 16 insertions, 15 deletions

diff --git a/cli/args/mod.rs b/cli/args/mod.rs
index 07906a86a..f905e186b 100644
--- a/cli/args/mod.rs
+++ b/cli/args/mod.rs
@@ -1576,6 +1576,11 @@ impl CliOptions {
       || self.workspace().has_unstable("bare-node-builtins")
   }
 
+  pub fn unstable_detect_cjs(&self) -> bool {
+    self.flags.unstable_config.detect_cjs
+      || self.workspace().has_unstable("detect-cjs")
+  }
+
   fn byonm_enabled(&self) -> bool {
     // check if enabled via unstable
     self.node_modules_dir().ok().flatten() == Some(NodeModulesDirMode::Manual)
@@ -1620,21 +1625,17 @@ impl CliOptions {
       });
 
     if !from_config_file.is_empty() {
-      // collect unstable granular flags
-      let mut all_valid_unstable_flags: Vec<&str> =
-        crate::UNSTABLE_GRANULAR_FLAGS
-          .iter()
-          .map(|granular_flag| granular_flag.name)
-          .collect();
-
-      let mut another_unstable_flags = Vec::from([
-        "sloppy-imports",
-        "byonm",
-        "bare-node-builtins",
-        "fmt-component",
-      ]);
-      // add more unstable flags to the same vector holding granular flags
-      all_valid_unstable_flags.append(&mut another_unstable_flags);
+      let all_valid_unstable_flags: Vec<&str> = crate::UNSTABLE_GRANULAR_FLAGS
+        .iter()
+        .map(|granular_flag| granular_flag.name)
+        .chain([
+          "sloppy-imports",
+          "byonm",
+          "bare-node-builtins",
+          "fmt-component",
+          "detect-cjs",
+        ])
+        .collect();
 
       // check and warn if the unstable flag of config file isn't supported, by
       // iterating through the vector holding the unstable flags