feat(cli): metadata can live in a separate file (WIP)

packages/@aws-cdk/cloud-assembly-schema/lib/cloud-assembly/schema.ts

@@ -81,10 +81,24 @@ export interface ArtifactManifest {
   /**
    * Associated metadata.
    *
+   * Metadata can be stored directly in the assembly manifest, as well as in a
+   * separate file (see `additionalMetadataFile`). It should prefer to be stored
+   * in the additional file, as that will reduce the size of the assembly
+   * manifest in cases of a lot of metdata (which CDK does emit by default).
+   *
    * @default - no metadata.
    */
   readonly metadata?: { [path: string]: MetadataEntry[] };
 
+  /**
+   * A file with additional metadata entries.
+   *
+   * The schema of this file is exactly the same as the type of the `metadata` field.
+   *
+   * @default - no additional metadata
+   */
+  readonly additionalMetadataFile?: string;
+
   /**
    * IDs of artifacts that must be deployed before this artifact.
    *

packages/@aws-cdk/cloud-assembly-schema/schema/cloud-assembly.schema.json

@@ -49,7 +49,7 @@
                     "type": "string"
                 },
                 "metadata": {
-                    "description": "Associated metadata. (Default - no metadata.)",
+                    "description": "Associated metadata.\n\nMetadata can be stored directly in the assembly manifest, as well as in a\nseparate file (see `additionalMetadataFile`). It should prefer to be stored\nin the additional file, as that will reduce the size of the assembly\nmanifest in cases of a lot of metdata (which CDK does emit by default). (Default - no metadata.)",
                     "type": "object",
                     "additionalProperties": {
                         "type": "array",
@@ -58,6 +58,10 @@
                         }
                     }
                 },
+                "additionalMetadataFile": {
+                    "description": "A file with additional metadata entries.\n\nThe schema of this file is exactly the same as the type of the `metadata` field. (Default - no additional metadata)",
+                    "type": "string"
+                },
                 "dependencies": {
                     "description": "IDs of artifacts that must be deployed before this artifact. (Default - no dependencies.)",
                     "type": "array",

packages/@aws-cdk/cloud-assembly-schema/schema/version.json

@@ -1,4 +1,4 @@
 {
-  "schemaHash": "96958a4c40e0a00e850f0c14dd6e9c0fc8db0b075f1f155cea41ab198c0514be",
-  "revision": 43
+  "schemaHash": "e03b716ea6f59e089369ce279c03a194917456d466994d434e5f9f366b745f12",
+  "revision": 44
 }

packages/@aws-cdk/toolkit-lib/lib/api/utilities/index.ts

@@ -0,0 +1 @@
+export * from './manifest-reading';

packages/@aws-cdk/toolkit-lib/lib/api/utilities/manifest-reading.ts

@@ -0,0 +1,21 @@
+import * as fs from 'fs';
+import * as path from 'path';
+import type { ArtifactManifest, MetadataEntry } from '@aws-cdk/cloud-assembly-schema';
+
+/**
+ * Read the metadata for the given artifact
+ *
+ * You must use this instead of accessing `ArtifactManifest.metadata`
+ * directly; this can also deal with the case of where the metadata
+ * has been written to a file.
+ */
+export function readArtifactMetadata(assemblyDirectory: string, x: ArtifactManifest): Record<string, MetadataEntry[]> {
+  const ret = {};
+  if (x.additionalMetadataFile) {
+    Object.assign(ret, JSON.parse(fs.readFileSync(path.join(assemblyDirectory, x.additionalMetadataFile), 'utf-8')));
+  }
+  // FIXME: Conflicting paths
+  // FIXME: Rewrite stack tags
+  Object.assign(ret, x.metadata);
+  return ret;
+}