fix(cli-integ): interactive cdk import test is unstable (#76)

Various enhancements in this PR:

- Don't register a callback on `stderr` because it creates duplicate
output.
- Shift the interactions array before writing to `stdin` to prevent
possible interaction reuse.
- On interaction match, reset the `lastLine` we match on to prevent
repeated matches due to tty echoing.
- Make prompt matching in `cdk import` test be more specific to the
requested input.

Author: iliapolo

packages/@aws-cdk-testing/cli-integ/lib/process.ts

@@ -90,9 +90,9 @@ class PtyProcess implements IProcess {
     this.process.onData((e) => callback(Buffer.from(e)));
   }
 
-  public onStderr(callback: (chunk: Buffer) => void): void {
-    // in a pty all streams are the same
-    return this.onStdout(callback);
+  public onStderr(_callback: (chunk: Buffer) => void): void {
+    // https://github.com/microsoft/node-pty/issues/71
+    throw new Error(`Cannot register callback for 'stderr'. A tty does not have separate output and error channels`);
   }
 
   public onExit(callback: (exitCode: number) => void): void {

packages/@aws-cdk-testing/cli-integ/lib/shell.ts

@@ -60,27 +60,42 @@ export async function shell(command: string[], options: ShellOptions = {}): Prom
       if (interaction) {
 
         if (interaction.prompt.test(lastLine.get())) {
+
           // subprocess expects a user input now.
-          // we have to write the input AFTER the child has started
-          // reading, so we do this with a small delay.
+          // first, shift the interactions to ensure the same interaction is not reused
+          remainingInteractions.shift();
+
+          // then, reset the last line to prevent repeated matches caused by tty echoing
+          lastLine.reset();
+
+          // now write the input with a slight delay to ensure
+          // the child process has already started reading.
           setTimeout(() => {
             child.writeStdin(interaction.input + (interaction.end ?? os.EOL));
-            remainingInteractions.shift();
           }, 500);
         }
 
       }
 
     });
 
-    child.onStderr(chunk => {
-      if (show === 'always') {
-        writeToOutputs(chunk.toString('utf-8'));
-      }
-      if (options.captureStderr ?? true) {
-        stderr.push(chunk);
-      }
-    });
+    if (tty && options.captureStderr === false) {
+      // in a tty stderr goes to the same fd as stdout
+      throw new Error(`Cannot disable 'captureStderr' in tty`);
+    }
+
+    if (!tty) {
+      // in a tty stderr goes to the same fd as stdout, so onStdout
+      // is sufficient.
+      child.onStderr(chunk => {
+        if (show === 'always') {
+          writeToOutputs(chunk.toString('utf-8'));
+        }
+        if (options.captureStderr ?? true) {
+          stderr.push(chunk);
+        }
+      });
+    }
 
     child.onError(reject);
 
@@ -309,4 +324,8 @@ class LastLine {
   public get(): string {
     return this.lastLine;
   }
+
+  public reset() {
+    this.lastLine = '';
+  }
 }

packages/@aws-cdk-testing/cli-integ/tests/cli-integ-tests/cdk-import-interactive.integtest.ts

@@ -27,14 +27,18 @@ integTest('cdk import prompts the user for sns topic arns', withDefaultFixture(a
     await fixture.cdk(['import', fullStackName], {
       interact: [
         {
-          prompt: /\(empty to skip\)/,
+          prompt: /Topic1.*\(empty to skip\):/,
           input: topic1Arn,
         },
         {
-          prompt: /\(empty to skip\)/,
+          prompt: /Topic2.*\(empty to skip\):/,
           input: topic2Arn,
         }
-      ]
+      ],
+      modEnv: {
+        // disable coloring because it messes up prompt matching.
+        FORCE_COLOR: '0'
+      }
     });
 
     // assert the stack now has the two topics