Don't add code if no environment variables (#255)

## Before
<img width="1867" alt="Screenshot 2022-11-28 at 14 38 51"
src="https://user-images.githubusercontent.com/88345179/204292549-70892b09-1381-4de6-b37c-732daea8ac02.png">

## After
<img width="2233" alt="Screenshot 2022-11-28 at 14 39 34"
src="https://user-images.githubusercontent.com/88345179/204292583-fd24809e-0613-4f03-a903-c78c90acec7c.png">

Author: kartikgupta-db

packages/databricks-vscode/src/run/DatabricksRuntime.test.ts

@@ -114,7 +114,7 @@ describe(__filename, () => {
         assert(outputs[5].text.includes("Done"));
     });
 
-    it("should have the right code", async () => {
+    it("should have the right code with env vars", async () => {
         await runtime.start("/Desktop/workspaces/hello.py", [], {TEST: "TEST"});
 
         const code = capture(executionContextMock.execute).first()[0];
@@ -124,6 +124,21 @@ describe(__filename, () => {
 import sys; sys.path.append("/Workspace/Repos/[email protected]/test")
 import sys; sys.argv = ['/Workspace/Repos/[email protected]/test/hello.py'];
 import os; os.environ["TEST"]='TEST';
+import logging; logger = spark._jvm.org.apache.log4j; logging.getLogger("py4j.java_gateway").setLevel(logging.ERROR)
+print('43')`
+        );
+    });
+
+    it("should have the right code without env vars", async () => {
+        await runtime.start("/Desktop/workspaces/hello.py", [], {});
+
+        const code = capture(executionContextMock.execute).first()[0];
+        assert.equal(
+            code,
+            `import os; os.chdir("/Workspace/Repos/[email protected]/test");
+import sys; sys.path.append("/Workspace/Repos/[email protected]/test")
+import sys; sys.argv = ['/Workspace/Repos/[email protected]/test/hello.py'];
+
 import logging; logger = spark._jvm.org.apache.log4j; logging.getLogger("py4j.java_gateway").setLevel(logging.ERROR)
 print('43')`
         );

packages/databricks-vscode/src/run/DatabricksRuntime.ts

@@ -274,7 +274,9 @@ export class DatabricksRuntime implements Disposable {
                 .map((arg) => this.escapePythonString(arg))
                 .join("', '")}'];`,
 
-            `import os; ${envVarSetCmds.join("; ")};`,
+            envVarSetCmds.length !== 0
+                ? `import os; ${envVarSetCmds.join("; ")};`
+                : "",
 
             // Set log level to "ERROR". See https://kb.databricks.com/notebooks/cmd-c-on-object-id-p0.html
             `import logging; logger = spark._jvm.org.apache.log4j; logging.getLogger("py4j.java_gateway").setLevel(logging.ERROR)`,