fix: "duplicate Export names" error deploying nested stacks with Fn::Join exports#1307
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aws-cdk-automation merged 5 commits intomainfrom Apr 3, 2026
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…oin exports\n\nWhen IncludeNestedStacks is true, CloudFormation collapses all Fn::Join\nexport names to {{IntrinsicFunction://Fn::Join}}, causing a false\nduplicate export name error when multiple nested stacks have Fn::Join\nexports with runtime references.
…eation\n\nCloudFormation cannot resolve intrinsic functions (like Fn::Join) in\nexport names at validation time when IncludeNestedStacks is true. It\ncollapses all such exports to the same placeholder, causing a false\n\"duplicate Export names\" error.\n\nReverts the IncludeNestedStacks addition from the deploy changeset path.\nThe diff changeset path retains it since --method=auto already falls\nback to template-based diff on error.
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Internal reference: D423570178 |
mrgrain
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mrgrain
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…stedStacks in deploy path" This reverts commit 7409264.
…tedStacks The --force deploy assertion expected CloudFormation to report "no changes" for nested stacks, which only works with IncludeNestedStacks. Without it, CloudFormation always executes the changeset for nested stacks. Update the assertion to expect a new changeset instead.
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CDK CLI v2.1116.0 added
IncludeNestedStacks: trueto the deploy changeset creation path (PR #1292). This tells CloudFormation to validate all nested stack templates together when creating a changeset.However, CloudFormation cannot resolve intrinsic functions at changeset validation time. When multiple nested stacks use
Fn::Join(or similar intrinsics) to build export names with runtime references, CloudFormation collapses all of them to the same placeholder{{IntrinsicFunction://Fn::Join}}and reports a false "duplicate Export names" error. This affects patterns like the Amplify GraphQL API construct which usesFn::Joinwith an API ID to generate unique export names across nested stacks.This PR removes
IncludeNestedStacksfrom the deploy changeset path, reverting to the pre-v2.1116.0 behavior. The diff changeset path (cdk diff --method=change-set) retainsIncludeNestedStackssince--method=auto(the default) already falls back to template-based diff on error, and changeset diff didn't work for any nested stacks in previous versions so the current behavior is strictly an improvement.Internal reference D423570178
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