fix(cli): stop processing on metadata errors (#3168)

The new stack selection short circuiting broke stack error checking,
which happened further down in that function. Move that functionality
out as an explicit step to the CLI, as opposed to doing it implicitly
as part of 'selectStacks'.

NOTE: no test here, should be an integration test but the test will fail
on the previous release so created a ticket for it.

packages/aws-cdk/bin/cdk.ts

@@ -281,6 +281,8 @@ async function initCommandLine() {
       defaultBehavior: DefaultSelection.AllStacks
     });
 
+    appStacks.processMetadata(stacks);
+
     // if we have a single stack, print it to STDOUT
     if (stacks.length === 1) {
       return stacks[0].template;

packages/aws-cdk/lib/api/cxapp/stacks.ts

@@ -164,9 +164,6 @@ export class AppStacks {
     // Filter original array because it is in the right order
     const selectedList = stacks.filter(s => selectedStacks.has(s.name));
 
-    // Only check selected stacks for errors
-    this.processMessages(selectedList);
-
     return selectedList;
   }
 
@@ -269,7 +266,7 @@ export class AppStacks {
   /**
    * Extracts 'aws:cdk:warning|info|error' metadata entries from the stack synthesis
    */
-  private processMessages(stacks: cxapi.CloudFormationStackArtifact[]) {
+  public processMetadata(stacks: cxapi.CloudFormationStackArtifact[]) {
     let warnings = false;
     let errors = false;
 

packages/aws-cdk/lib/cdk-toolkit.ts

@@ -81,6 +81,8 @@ export class CdkToolkit {
       defaultBehavior: DefaultSelection.OnlySingle
     });
 
+    this.appStacks.processMetadata(stacks);
+
     for (const stack of stacks) {
       if (stacks.length !== 1) { highlight(stack.name); }
       if (!stack.environment) {

packages/aws-cdk/test/api/test.stacks.ts

@@ -14,6 +14,7 @@ export = testCase({
     const selected = await stacks.selectStacks(['withouterrors'], {
       defaultBehavior: DefaultSelection.AllStacks
     });
+    stacks.processMetadata(selected);
 
     // THEN
     test.equal(selected[0].template.resource, 'noerrorresource');
@@ -27,9 +28,10 @@ export = testCase({
 
     // WHEN
     try {
-      await stacks.selectStacks(['witherrors'], {
+      const selected = await stacks.selectStacks(['witherrors'], {
         defaultBehavior: DefaultSelection.AllStacks
       });
+      stacks.processMetadata(selected);
 
       test.ok(false, 'Did not get exception');
     } catch (e) {