fix(compile): prevent setting unstable feature twice (#24381)

Prevent panic when enabling a feature that is already enabled by
removing duplicate features.

Closes #22015

---------

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

cli/args/mod.rs

@@ -1773,14 +1773,28 @@ impl CliOptions {
       .map(|c| c.json.unstable.clone())
       .unwrap_or_default();
 
-    from_config_file.extend_from_slice(&self.flags.unstable_config.features);
+    self
+      .flags
+      .unstable_config
+      .features
+      .iter()
+      .for_each(|feature| {
+        if !from_config_file.contains(feature) {
+          from_config_file.push(feature.to_string());
+        }
+      });
 
     if *DENO_FUTURE {
-      from_config_file.extend_from_slice(&[
+      let future_features = [
         deno_runtime::deno_ffi::UNSTABLE_FEATURE_NAME.to_string(),
         deno_runtime::deno_fs::UNSTABLE_FEATURE_NAME.to_string(),
         deno_runtime::deno_webgpu::UNSTABLE_FEATURE_NAME.to_string(),
-      ]);
+      ];
+      future_features.iter().for_each(|future_feature| {
+        if !from_config_file.contains(future_feature) {
+          from_config_file.push(future_feature.to_string());
+        }
+      });
     }
 
     from_config_file

tests/specs/compile/repetitive_unstable_flag/.gitignore

@@ -0,0 +1,2 @@
+out.exe
+out

tests/specs/compile/repetitive_unstable_flag/__test__.jsonc

@@ -0,0 +1,13 @@
+{
+  "steps": [
+    {
+      "args": "compile --unstable-kv -A --output out main.ts",
+      "output": "compile.out"
+    },
+    {
+      "commandName": "./out",
+      "args": [],
+      "output": "main.out"
+    }
+  ]
+}

tests/specs/compile/repetitive_unstable_flag/compile.out

@@ -0,0 +1,2 @@
+Check [WILDCARD]main.ts
+Compile [WILDCARD]main.ts to out[WILDCARD]

tests/specs/compile/repetitive_unstable_flag/deno.json

@@ -0,0 +1,3 @@
+{
+  "unstable": ["kv"]
+}

tests/specs/compile/repetitive_unstable_flag/main.out

@@ -0,0 +1 @@
+Duplicate unstable feature issue is resolved as you can see

tests/specs/compile/repetitive_unstable_flag/main.ts

@@ -0,0 +1 @@
+console.log("Duplicate unstable feature issue is resolved as you can see");