Never replace

Author: Kartik Raj

.vscode/launch.json

@@ -160,7 +160,7 @@
                 "--ui=tdd",
                 "--recursive",
                 "--colors",
-                //"--grep", "<suite name>",
+                "--grep", "Terminal Environment Variable Collection",
                 "--timeout=300000"
             ],
             "outFiles": ["${workspaceFolder}/out/**/*.js", "!${workspaceFolder}/**/node_modules**/*"],

src/test/interpreters/activation/terminalEnvVarCollectionService.unit.test.ts

@@ -216,7 +216,7 @@ suite('Terminal Environment Variable Collection Service', () => {
         assert.deepEqual(opts, { applyAtProcessCreation: false, applyAtShellIntegration: true });
     });
 
-    test('Prepend PATH instead of replacing it, where possible', async () => {
+    test('Prepend only "prepend portion of PATH" where applicable', async () => {
         const processEnv = { PATH: 'hello/1/2/3' };
         reset(environmentActivationService);
         when(environmentActivationService.getProcessEnvironmentVariables(anything(), anything())).thenResolve(
@@ -248,6 +248,38 @@ suite('Terminal Environment Variable Collection Service', () => {
         assert.deepEqual(opts, { applyAtProcessCreation: true, applyAtShellIntegration: true });
     });
 
+    test('Prepend full PATH otherwise', async () => {
+        const processEnv = { PATH: 'hello/1/2/3' };
+        reset(environmentActivationService);
+        when(environmentActivationService.getProcessEnvironmentVariables(anything(), anything())).thenResolve(
+            processEnv,
+        );
+        const finalPath = 'hello/3/2/1';
+        const envVars: NodeJS.ProcessEnv = { PATH: finalPath };
+        when(
+            environmentActivationService.getActivatedEnvironmentVariables(
+                anything(),
+                undefined,
+                undefined,
+                customShell,
+            ),
+        ).thenResolve(envVars);
+
+        when(collection.replace(anything(), anything(), anything())).thenResolve();
+        when(collection.delete(anything())).thenResolve();
+        let opts: EnvironmentVariableMutatorOptions | undefined;
+        when(collection.prepend('PATH', anything(), anything())).thenCall((_, _v, o) => {
+            opts = o;
+        });
+
+        await terminalEnvVarCollectionService._applyCollection(undefined, customShell);
+
+        verify(collection.clear()).once();
+        verify(collection.prepend('PATH', finalPath, anything())).once();
+        verify(collection.replace('PATH', anything(), anything())).never();
+        assert.deepEqual(opts, { applyAtProcessCreation: true, applyAtShellIntegration: true });
+    });
+
     test('Verify envs are not applied if env activation is disabled', async () => {
         const envVars: NodeJS.ProcessEnv = { CONDA_PREFIX: 'prefix/to/conda', ...process.env };
         when(