fix(core): use default account/region when environment is not specified

packages/@aws-cdk/cdk/lib/stack.ts

@@ -505,17 +505,24 @@ export class Stack extends Construct implements ITaggable {
    */
   private parseEnvironment(env: Environment = {}) {
     // if an environment property is explicitly specified when the stack is
-    // created, it will be used as concrete values for all intents.
-    const region = env.region;
-    const account = env.account;
+    // created, it will be used as concrete values for all intents. if not, use
+    // tokens for account and region but they do not need to be scoped, the only
+    // situation in which export/fn::importvalue would work if { Ref:
+    // "AWS::AccountId" } is the same for provider and consumer anyway.
+    const region = env.region || Aws.region;
+    const account = env.account || Aws.accountId;
+
+    // temporary fix for #2853, eventually behavior will be based on #2866.
+    // set the cloud assembly manifest environment spec of this stack to use the
+    // default account/region from the toolkit in case account/region are undefined or
+    // unresolved (i.e. tokens).
+    const envAccount = !Token.isUnresolved(account) ? account : Context.getDefaultAccount(this) || 'unknown-account';
+    const envRegion  = !Token.isUnresolved(region)  ? region  : Context.getDefaultRegion(this)  || 'unknown-region';
 
-    // account and region do not need to be scoped, the only situation in which
-    // export/fn::importvalue would work if { Ref: "AWS::AccountId" } is the
-    // same for provider and consumer anyway.
     return {
       account: account || Aws.accountId,
       region: region || Aws.region,
-      environment: EnvironmentUtils.format(account || 'unknown-account', region || 'unknown-region')
+      environment: EnvironmentUtils.format(envAccount, envRegion)
     };
   }
 
@@ -651,9 +658,11 @@ function cfnElements(node: IConstruct, into: CfnElement[] = []): CfnElement[] {
 import { Arn, ArnComponents } from './arn';
 import { CfnElement } from './cfn-element';
 import { CfnResource, TagType } from './cfn-resource';
+import { Context } from './context';
 import { CfnReference } from './private/cfn-reference';
 import { Aws, ScopedAws } from './pseudo';
 import { ITaggable, TagManager } from './tag-manager';
+import { Token } from './token';
 
 /**
  * Find all resources in a set of constructs

packages/@aws-cdk/cdk/test/test.environment.ts

@@ -1,6 +1,7 @@
 import { DEFAULT_ACCOUNT_CONTEXT_KEY, DEFAULT_REGION_CONTEXT_KEY } from '@aws-cdk/cx-api';
+import cxapi = require('@aws-cdk/cx-api');
 import { Test } from 'nodeunit';
-import { App, Stack, Token } from '../lib';
+import { App, Aws, Stack, Token } from '../lib';
 
 export = {
   'By default, environment region and account are not defined and resolve to intrinsics'(test: Test) {
@@ -40,4 +41,140 @@ export = {
 
     test.done();
   },
+
+  'environment defaults': {
+    'default-account-unknown-region'(test: Test) {
+      // GIVEN
+      const app = new App();
+
+      // WHEN
+      app.node.setContext(cxapi.DEFAULT_ACCOUNT_CONTEXT_KEY, 'my-default-account');
+      const stack = new Stack(app, 'stack');
+
+      // THEN
+      test.deepEqual(stack.resolve(stack.account), { Ref: 'AWS::AccountId' }); // TODO: after we implement #2866 this should be 'my-default-account'
+      test.deepEqual(stack.resolve(stack.region), { Ref: 'AWS::Region' });
+      test.deepEqual(app.synth().getStack(stack.stackName).environment, {
+        account: 'my-default-account',
+        region: 'unknown-region',
+        name: 'aws://my-default-account/unknown-region'
+      });
+
+      test.done();
+    },
+
+    'default-account-explicit-region'(test: Test) {
+      // GIVEN
+      const app = new App();
+
+      // WHEN
+      app.node.setContext(cxapi.DEFAULT_ACCOUNT_CONTEXT_KEY, 'my-default-account');
+      const stack = new Stack(app, 'stack', { env: { region: 'explicit-region' }});
+
+      // THEN
+      test.deepEqual(stack.resolve(stack.account), { Ref: 'AWS::AccountId' }); // TODO: after we implement #2866 this should be 'my-default-account'
+      test.deepEqual(stack.resolve(stack.region), 'explicit-region');
+      test.deepEqual(app.synth().getStack(stack.stackName).environment, {
+        account: 'my-default-account',
+        region: 'explicit-region',
+        name: 'aws://my-default-account/explicit-region'
+      });
+
+      test.done();
+    },
+
+    'explicit-account-explicit-region'(test: Test) {
+      // GIVEN
+      const app = new App();
+
+      // WHEN
+      app.node.setContext(cxapi.DEFAULT_ACCOUNT_CONTEXT_KEY, 'my-default-account');
+      const stack = new Stack(app, 'stack', { env: {
+        account: 'explicit-account',
+        region: 'explicit-region'
+      }});
+
+      // THEN
+      test.deepEqual(stack.resolve(stack.account), 'explicit-account');
+      test.deepEqual(stack.resolve(stack.region), 'explicit-region');
+      test.deepEqual(app.synth().getStack(stack.stackName).environment, {
+        account: 'explicit-account',
+        region: 'explicit-region',
+        name: 'aws://explicit-account/explicit-region'
+      });
+
+      test.done();
+    },
+
+    'default-account-default-region'(test: Test) {
+      // GIVEN
+      const app = new App();
+
+      // WHEN
+      app.node.setContext(cxapi.DEFAULT_ACCOUNT_CONTEXT_KEY, 'my-default-account');
+      app.node.setContext(cxapi.DEFAULT_REGION_CONTEXT_KEY, 'my-default-region');
+      const stack = new Stack(app, 'stack');
+
+      // THEN
+      test.deepEqual(stack.resolve(stack.account), { Ref: 'AWS::AccountId' }); // TODO: after we implement #2866 this should be 'my-default-account'
+      test.deepEqual(stack.resolve(stack.region), { Ref: 'AWS::Region' });     // TODO: after we implement #2866 this should be 'my-default-region'
+      test.deepEqual(app.synth().getStack(stack.stackName).environment, {
+        account: 'my-default-account',
+        region: 'my-default-region',
+        name: 'aws://my-default-account/my-default-region'
+      });
+
+      test.done();
+    },
+
+    'token-account-token-region-no-defaults'(test: Test) {
+      // GIVEN
+      const app = new App();
+
+      // WHEN
+      app.node.setContext(cxapi.DEFAULT_ACCOUNT_CONTEXT_KEY, 'my-default-account');
+      app.node.setContext(cxapi.DEFAULT_REGION_CONTEXT_KEY, 'my-default-region');
+      const stack = new Stack(app, 'stack', {
+        env: {
+          account: Aws.accountId,
+          region: Aws.region
+        }
+      });
+
+      // THEN
+      test.deepEqual(stack.resolve(stack.account), { Ref: 'AWS::AccountId' });
+      test.deepEqual(stack.resolve(stack.region), { Ref: 'AWS::Region' });
+      test.deepEqual(app.synth().getStack(stack.stackName).environment, {
+        account: 'my-default-account',
+        region: 'my-default-region',
+        name: 'aws://my-default-account/my-default-region'
+      });
+
+      test.done();
+    },
+
+    'token-account-token-region-with-defaults'(test: Test) {
+      // GIVEN
+      const app = new App();
+
+      // WHEN
+      const stack = new Stack(app, 'stack', {
+        env: {
+          account: Aws.accountId,
+          region: Aws.region
+        }
+      });
+
+      // THEN
+      test.deepEqual(stack.resolve(stack.account), { Ref: 'AWS::AccountId' });
+      test.deepEqual(stack.resolve(stack.region), { Ref: 'AWS::Region' });
+      test.deepEqual(app.synth().getStack(stack.stackName).environment, {
+        account: 'unknown-account',
+        region: 'unknown-region',
+        name: 'aws://unknown-account/unknown-region'
+      });
+
+      test.done();
+    }
+  },
 };