Launch: env takes priority over envFile (#5537)

This PR changes the way debug/no-debug launch works with the C# extension so that environment variables added via `env` will take precedence over environment variables added via `envFile`.

This resolves #5413

Author: askazakov

src/coreclr-debug/ParsedEnvironmentFile.ts

@@ -26,14 +26,19 @@ export class ParsedEnvironmentFile {
         }
 
         let parseErrors: string[] = [];
-        let env = initialEnv ?? {};
+        let safeInitialEnv = initialEnv ?? {};
+        let env = {...safeInitialEnv};
 
         content.split("\n").forEach(line => {
             // Split the line between key and value
             const match = line.match(/^\s*([\w\.\-]+)\s*=\s*(.*)?\s*$/);
 
             if (match !== null) {
                 const key = match[1];
+                if (safeInitialEnv[key] !== undefined) {
+                    return;
+                }
+
                 let value = match[2] ?? "";
                 if (value.length > 0 && value.charAt(0) === '"' && value.charAt(value.length - 1) === '"') {
                     value = value.replace(/\\n/gm, "\n");

test/unitTests/ParsedEnvironmentFile.test.ts

@@ -46,24 +46,35 @@ MyName2=Value2
         result.Env["MyName2"].should.equal("Value2");
     });
 
-    test("Update variable", () => {
+    test("Not override variables", () => {
         const content = `
-MyName1=Value1
+CommonKey=NewValue
 MyName2=Value2
 
 `;
         const initialEnv = {
-            "MyName1": "Value7",
+            "CommonKey": "InitialValue",
             "ThisShouldNotChange": "StillHere"
         };
         const result = ParsedEnvironmentFile.CreateFromContent(content, "TestEnvFileName", initialEnv);
 
         expect(result.Warning).to.be.undefined;
-        result.Env["MyName1"].should.equal("Value1");
+        result.Env["CommonKey"].should.equal("InitialValue");
         result.Env["MyName2"].should.equal("Value2");
         result.Env["ThisShouldNotChange"].should.equal("StillHere");
     });
 
+    test("Take last value", () => {
+        const content = `
+Key=FirstValue
+Key=SecondValue
+`;
+        const result = ParsedEnvironmentFile.CreateFromContent(content, "TestEnvFileName", undefined);
+
+        expect(result.Warning).to.be.undefined;
+        result.Env["Key"].should.equal("SecondValue");
+    });
+
     test("Handle comments", () => {
         const content = `# This is an environment file
 MyName1=Value1