CDK StableNameStack

StableNameStack.ts

import { CfnElement, CfnResource, Stack } from "@aws-cdk/core";
import { makeUniqueId } from "@aws-cdk/core/lib/private/uniqueid";
import { Node } from "constructs";
import * as assert from "assert";

const PINNED_RESOURCE_NAMES_CONTEXT_KEY = "pinnedLogicalIds";

type PinnedLogicalIds = { [segment: string]: PinnedLogicalIds | string };

export class StableNameStack extends Stack {
  protected allocateLogicalId(element: CfnElement): string {
    const pinnedLogicalIds: PinnedLogicalIds = Node.of(this).tryGetContext(PINNED_RESOURCE_NAMES_CONTEXT_KEY) ?? {};
    if (CfnResource.isCfnResource(element)) {
      const path = element.node.path;
      const found = find(pinnedLogicalIds, path.split("/"), element);
      if (found) {
        return found;
      }
    }

    return super.allocateLogicalId(element);
  }
}

function find(pinnedLogicalIds: PinnedLogicalIds, pathSegments: string[], resource: CfnResource): string | undefined {
  // You can match type with "!AWS::EC2::VPC", or "!EC2::VPC", or "!VPC", if it is not ambiguous
  const typeSegments = resource.cfnResourceType.split("::");
  for (let i = typeSegments.length - 1; i >= 0; i--) {
    const tails = typeSegments.slice(i).join("::");
    const findByType = pinnedLogicalIds[`!${tails}`];
    if (findByType !== undefined) {
      assert(typeof findByType === "string");
      return findByType;
    }
  }

  for (let i = pathSegments.length; i > 0; i--) {
    const prefix = pathSegments.slice(0, i).join("/");
    const rest = pathSegments.slice(i);
    const lookup = pinnedLogicalIds[prefix];
    if (typeof lookup === "string") {
      if (lookup.startsWith("@")) {
        // path prefix rewrite
        const path = lookup.slice(1).split("/");
        return makeUniqueId([...path, ...rest]);
      }
      return lookup;
    } else if (lookup !== undefined) {
      const found = find(lookup, rest, resource);
      if (found) {
        return found;
      }
    }
  }

  return undefined;
}

In cdk.json, you can pin logical Ids.

{
  "context": {
    "pinnedLogicalIds": {
      // You can pin a resource name in a path
      "StackA/Path/To/Resource": "OldNameToKeep",
      "StackA/Path": {
        "To/Construct": {
          // You can match type with '!'.
          // 'AWS::EC2::VPC' type resource that matches 'StackA/Path/To/Construct/*' will get 'Vpc'.
          "!AWS::EC2::VPC": "Vpc",
          // You can omit 'EC2', 'AWS' if they are not ambiguous in this context.
          "!EC2::InternetGateway": "IGW",
          "!VPCGatewayAttachment": "VPCGW",
          // You can pin a tree with '@'.
          // All resources 'StackA/Path/To/Construct/Of/Construct/*' will named as if they were in 'StackA/Previous/Path/Construct/*'
          "Of/Construct": "@Previous/Path/Construct"
        }
      }
    }
  }
}

What about stack.renameLogicalId()

I wanted to rename all resources in a construct tree, and wanted to make less changes as possible. What would be different with it?

Got it, so what I would recommend is overriding Stack.allocateLogicalId.

Thanks 👍

I'll share my modification:

     if (typeof lookup === 'string') {
       if (lookup.startsWith('@')) {
         // path prefix rewrite
-        const path = lookup.slice(1).split("/");
+        const path = lookup.slice(1).split("/").filter(s => !!s);
         return makeUniqueId([...path, ...rest]);
       }
       return lookup;

to handle configuration like:

{
  "context": {
    "pinnedLogicalIds": {
      "Stack/A": "@"
    }
  }
}

CDK v2 version:

import { CfnElement, CfnResource, Names, Stack } from 'aws-cdk-lib/core';
import { Construct } from 'constructs';
import * as assert from 'node:assert';

const PINNED_RESOURCE_NAMES_CONTEXT_KEY = 'pinnedLogicalIds';

type PinnedLogicalIds = { [segment: string]: PinnedLogicalIds | string };

export class StableNameStack extends Stack {
  protected allocateLogicalId(element: CfnElement): string {
    const pinnedLogicalIds: PinnedLogicalIds = this.node.tryGetContext(PINNED_RESOURCE_NAMES_CONTEXT_KEY) ?? {};
    if (CfnResource.isCfnResource(element)) {
      const path = element.node.path;
      const found = find(pinnedLogicalIds, path.split('/'), element);
      if (found) {
        return found;
      }
    }

    return super.allocateLogicalId(element);
  }
}

function find(pinnedLogicalIds: PinnedLogicalIds, pathSegments: string[], resource: CfnResource): string | undefined {
  // You can match type with '!AWS::EC2::VPC', or '!EC2::VPC', or '!VPC', if it is not ambiguous
  const typeSegments = resource.cfnResourceType.split('::');
  for (let i = typeSegments.length - 1; i >= 0; i--) {
    const tails = typeSegments.slice(i).join('::');
    const findByType = pinnedLogicalIds[`!${tails}`];
    if (findByType !== undefined) {
      assert.ok(typeof findByType === 'string');
      return findByType;
    }
  }

  for (let i = pathSegments.length; i > 0; i--) {
    const prefix = pathSegments.slice(0, i).join('/');
    const rest = pathSegments.slice(i);
    const lookup = pinnedLogicalIds[prefix];
    if (typeof lookup === 'string') {
      if (lookup.startsWith('@')) {
        // path prefix rewrite
        const path = lookup.slice(1).split('/').filter(s => !!s);;
        return makeUniqueId([...path, ...rest]);
      }
      return lookup;
    } else if (lookup !== undefined) {
      const found = find(lookup, rest, resource);
      if (found) {
        return found;
      }
    }
  }

  return undefined;
}

// makeUniqueId function must behave the same as the one at core lib.
// https://github.com/aws/aws-cdk/blob/7373cb9fd35cd4b0ddcbab3837c18babfd8e1b6f/packages/aws-cdk-lib/core/lib/private/uniqueid.ts#L32
export function makeUniqueId(components: string[]) {
  const tree = dummyConstructTree(components);
  if (tree == undefined) return '';
  return Names.uniqueId(tree);
}

function dummyConstructTree(components: string[]): Construct {
  const last = components.at(-1);
  if (last == undefined) return new Construct(undefined as any, 'dummy');
  return new Construct(dummyConstructTree(components.slice(0, -1)), last);
}