fix(cdk): cdk diff --quiet to print stack name when there is diffs

[sakurai-ryo]

Issue # (if applicable)

Closes #27128

Reason for this change

The --quiet flag on the cdk diff command prevents the stack name and default message from being printed when no diff exists.
If diffs exist, the stack name and diffs are expected to be printed, but currently, the stack name is not printed, and it is difficult to determine which stack the diff is for.

for example:

$ cdk diff --quiet
Resources
[~] AWS::S3::Bucket MyFirstBucket MyFirstBucketB8884501
 ├─ [~] DeletionPolicy
 │   ├─ [-] Delete
 │   └─ [+] Retain
 └─ [~] UpdateReplacePolicy
     ├─ [-] Delete
     └─ [+] Retain


✨  Number of stacks with differences: 1

This PR will fix to print the stack name when the --quiet flag is specified and diffs exist.

Description of changes

Changed the position of the fullDiff function call.
It is possible to output the stack name in the printSecurityDiff or printStackDiff functions, but since the message has already been output before these functions are called, the stack name must be output first.
I think it would be more user-friendly to have all messages after the output of the stack name, but if this is not the case, please point this out.

Description of how you validated changes

I added a unit test to confirm to print the stack name when diff exists.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[sakurai-ryo]

I fixed a broken test. Originally, the test assumed there was no difference, but the specification stackNames: ['A', 'A'] actually implied a difference existed. The assertion not.toContain passed due to the presence or absence of ANSI escape sequences. To correct this, I changed the specification to stackNames: ['D'], where no difference exists, and I also removed the ANSI escape sequences from the assertion string.

aws-cdk/packages/aws-cdk/test/diff.test.ts

Line 57 in 10ed194

if (stackArtifact.stackName === 'D') {

[aws-cdk-automation]

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[sakurai-ryo]

Exemption Request: I think the unit tests cover the test for this change.

[sakurai-ryo]

In the previous PR, it was commented that the stack name output should be done in the printSecurityDiff function, but I decided to write it this way because we think it is more user-friendly to write all messages after the stack name output.
Please let me know if you have a better way to write it or if you have another opinion!

#28576 (comment)

[comcalvi]

I agree that we should print all messages after the stack name output, so can we move all of those messages after the stack name output and move the stack name to printSecurityDiff?

[comcalvi]

If not, can you explain which messages are unable to be moved?

[sakurai-ryo]

Thanks @comcalvi.
I think such an implementation is possible.
I have one question:
I forgot to mention that in the current code, the messages generated during the changeset creation are displayed before the stack name.
Is this acceptable?

To fix this issue, it is necessary to control the display of the stack name based on the presence of a diff when the --quiet flag is true.
However, determining the diff requires creating a changeset (though there are cases where it is unnecessary), and messages are output during this process.
While it might be necessary to suppress these messages when the --quiet flag is true, debug messages are also output during the changeset creation process when the -v flag is specified.
We would need to allow cases where messages output during the changeset creation process appear before the stack name.

[sakurai-ryo]

For example, I am thinking of changing the printStackDiff function to look like this

export function printStackDiff(
  oldTemplate: any,
  newTemplate: cxapi.CloudFormationStackArtifact,
  strict: boolean,
  context: number,
  quiet: boolean,
+ stackName?: string,
  changeSet?: DescribeChangeSetOutput,
  isImport?: boolean,
  stream: FormatStream = process.stderr,
  nestedStackTemplates?: { [nestedStackLogicalId: string]: NestedStackTemplates }): number {
  let diff = fullDiff(oldTemplate, newTemplate.template, changeSet, isImport);

+  // must output the stack name if there are differences, even if quiet
+  if (stackName && (!quiet || !diff.isEmpty)) {
+    stream.write(format('Stack %s\n', chalk.bold(stackName)));
+  }

+  if (!quiet && isImport) {
+    stream.write('Parameters and rules created during migration do not affect resource configuration.\n');
+  }

  // detect and filter out mangled characters from the diff
  let filteredChangesCount = 0;
  if (diff.differenceCount && !strict) {
    const mangledNewTemplate = JSON.parse(mangleLikeCloudFormation(JSON.stringify(newTemplate.template)));
    const mangledDiff = fullDiff(oldTemplate, mangledNewTemplate, changeSet);
    filteredChangesCount = Math.max(0, diff.differenceCount - mangledDiff.differenceCount);
    if (filteredChangesCount > 0) {
      diff = mangledDiff;
    }
  }

  // filter out 'AWS::CDK::Metadata' resources from the template
  if (diff.resources && !strict) {
    diff.resources = diff.resources.filter(change => {
      if (!change) { return true; }
      if (change.newResourceType === 'AWS::CDK::Metadata') { return false; }
      if (change.oldResourceType === 'AWS::CDK::Metadata') { return false; }
      return true;
    });
  }

  let stackDiffCount = 0;
  if (!diff.isEmpty) {
    stackDiffCount++;
    formatDifferences(stream, diff, {
      ...logicalIdMapFromTemplate(oldTemplate),
      ...buildLogicalToPathMap(newTemplate),
    }, context);
  } else if (!quiet) {
    print(chalk.green('There were no differences'));
  }
  if (filteredChangesCount > 0) {
    print(chalk.yellow(`Omitted ${filteredChangesCount} changes because they are likely mangled non-ASCII characters. Use --strict to print them.`));
  }

  for (const nestedStackLogicalId of Object.keys(nestedStackTemplates ?? {})) {
    if (!nestedStackTemplates) {
      break;
    }
    const nestedStack = nestedStackTemplates[nestedStackLogicalId];
-    if (!quiet) {
-      stream.write(format('Stack %s\n', chalk.bold(nestedStack.physicalName ?? nestedStackLogicalId)));
-    }


    (newTemplate as any)._template = nestedStack.generatedTemplate;
    stackDiffCount += printStackDiff(
      nestedStack.deployedTemplate,
      newTemplate,
      strict,
      context,
      quiet,
+      nestedStack.physicalName ?? nestedStackLogicalId,
      undefined,
      isImport,
      stream,
      nestedStack.nestedStackTemplates,
    );
  }

  return stackDiffCount;
}

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[comcalvi]

I agree that we should print all messages after the stack name output, so can we move all of those messages after the stack name output and move the stack name to printSecurityDiff?

[comcalvi]

We should not be calling fullDiff across both this method and printSecurityDiff. I'd prefer we keep fullDiff in printSecurityDiff, and then move the stack print to printSecurityDiff.

[comcalvi]

If not, can you explain which messages are unable to be moved?