config-loader: add support for serializing and deserializing schema

packages/config-loader/src/index.ts

@@ -15,5 +15,6 @@
  */
 
 export { readEnvConfig, loadConfigSchema } from './lib';
+export type { ConfigSchema } from './lib';
 export { loadConfig } from './loader';
 export type { LoadConfigOptions } from './loader';

packages/config-loader/src/lib/index.ts

@@ -17,4 +17,4 @@
 export { readConfigFile } from './reader';
 export { readEnvConfig } from './env';
 export { readSecret } from './secrets';
-export { loadConfigSchema } from './schema';
+export * from './schema';

packages/config-loader/src/lib/schema/collect.ts

@@ -15,7 +15,11 @@
  */
 
 import fs from 'fs-extra';
-import { resolve as resolvePath, dirname } from 'path';
+import {
+  resolve as resolvePath,
+  relative as relativePath,
+  dirname,
+} from 'path';
 import { ConfigSchemaPackageEntry } from './types';
 
 type Item = {
@@ -36,8 +40,9 @@ export async function collectConfigSchemas(
 ): Promise<ConfigSchemaPackageEntry[]> {
   const visitedPackages = new Set<string>();
   const schemas = Array<ConfigSchemaPackageEntry>();
+  const currentDir = process.cwd();
 
-  async function process({ name, parentPath }: Item) {
+  async function processItem({ name, parentPath }: Item) {
     // Ensures that we only process each package once. We don't bother with
     // loading in schemas from duplicates of different versions, as that's not
     // supported by Backstage right now anyway. We may want to change that in
@@ -81,22 +86,22 @@ export async function collectConfigSchemas(
         );
         schemas.push({
           value,
-          path: pkgPath,
+          path: relativePath(currentDir, pkgPath),
         });
       } else {
         schemas.push({
           value: pkg.configSchema,
-          path: pkgPath,
+          path: relativePath(currentDir, pkgPath),
         });
       }
     }
 
     await Promise.all(
-      depNames.map(name => process({ name, parentPath: pkgPath })),
+      depNames.map(name => processItem({ name, parentPath: pkgPath })),
     );
   }
 
-  await Promise.all(packageNames.map(name => process({ name })));
+  await Promise.all(packageNames.map(name => processItem({ name })));
 
   return schemas;
 }

packages/config-loader/src/lib/schema/index.ts

@@ -15,3 +15,4 @@
  */
 
 export { loadConfigSchema } from './load';
+export type { ConfigSchema } from './types';

packages/config-loader/src/lib/schema/load.ts

@@ -14,15 +14,19 @@
  * limitations under the License.
  */
 
-import { AppConfig } from '@backstage/config';
+import { AppConfig, JsonObject } from '@backstage/config';
 import { compileConfigSchemas } from './compile';
 import { collectConfigSchemas } from './collect';
 import { filterByVisibility } from './filtering';
-import { ConfigSchema } from './types';
+import { ConfigSchema, ConfigSchemaPackageEntry } from './types';
 
-type Options = {
-  dependencies: string[];
-};
+type Options =
+  | {
+      dependencies: string[];
+    }
+  | {
+      serialized: JsonObject;
+    };
 
 /**
  * Loads config schema for a Backstage instance.
@@ -30,7 +34,19 @@ type Options = {
 export async function loadConfigSchema(
   options: Options,
 ): Promise<ConfigSchema> {
-  const schemas = await collectConfigSchemas(options.dependencies);
+  let schemas: ConfigSchemaPackageEntry[];
+
+  if ('dependencies' in options) {
+    schemas = await collectConfigSchemas(options.dependencies);
+  } else {
+    const { serialized } = options;
+    if (serialized?.backstageConfigSchemaVersion !== 1) {
+      throw new Error(
+        'Serialized configuration schema is invalid or has an invalid version number',
+      );
+    }
+    schemas = serialized.schemas as ConfigSchemaPackageEntry[];
+  }
 
   const validate = compileConfigSchemas(schemas);
 
@@ -54,5 +70,11 @@ export async function loadConfigSchema(
 
       return processedConfigs;
     },
+    serialize(): JsonObject {
+      return {
+        schemas,
+        backstageConfigSchemaVersion: 1,
+      };
+    },
   };
 }

packages/config-loader/src/lib/schema/types.ts

@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-import { AppConfig } from '@backstage/config';
-import { JSONSchema7 as JSONSchema } from 'json-schema';
+import { AppConfig, JsonObject } from '@backstage/config';
 
 /**
  * An sub-set of configuration schema.
@@ -24,7 +23,7 @@ export type ConfigSchemaPackageEntry = {
   /**
    * The configuration schema itself, as JSONSchema draft-07
    */
-  value: JSONSchema;
+  value: JsonObject;
   /**
    * The path that the configuration schema was discovered at.
    */
@@ -91,4 +90,6 @@ export type ConfigSchema = {
     appConfigs: AppConfig[],
     options?: ConfigProcessingOptions,
   ): AppConfig[];
+
+  serialize(): JsonObject;
 };