Merge pull request #4559 from kaos/kaos/cli-config-schema

backstage-cli: add config:schema command.

packages/cli/src/commands/config/schema.ts

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2021 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { Command } from 'commander';
+import { JSONSchema7 as JSONSchema } from 'json-schema';
+import { stringify as stringifyYaml } from 'yaml';
+import { loadCliConfig } from '../../lib/config';
+import { JsonObject } from '@backstage/config';
+import { mergeConfigSchemas } from '@backstage/config-loader';
+
+export default async (cmd: Command) => {
+  const { schema } = await loadCliConfig({
+    args: [],
+    fromPackage: cmd.package,
+    mockEnv: true,
+  });
+
+  const merged = mergeConfigSchemas(
+    (schema.serialize().schemas as JsonObject[]).map(
+      _ => _.value as JSONSchema,
+    ),
+  );
+
+  merged.title = 'Application Configuration Schema';
+  merged.description =
+    'This is the schema describing the structure of the app-config.yaml configuration file.';
+
+  if (cmd.format === 'json') {
+    process.stdout.write(`${JSON.stringify(merged, null, 2)}\n`);
+  } else {
+    process.stdout.write(`${stringifyYaml(merged)}\n`);
+  }
+};

packages/cli/src/commands/index.ts

@@ -170,6 +170,15 @@ export function registerCommands(program: CommanderStatic) {
     )
     .action(lazy(() => import('./config/validate').then(m => m.default)));
 
+  program
+    .command('config:schema')
+    .option(
+      '--package <name>',
+      'Only output config schema that applies to the given package',
+    )
+    .description('Print configuration schema')
+    .action(lazy(() => import('./config/schema').then(m => m.default)));
+
   program
     .command('versions:bump')
     .description('Bump Backstage packages to the latest versions')

packages/cli/src/lib/config.ts

@@ -48,8 +48,10 @@ export async function loadCliConfig(options: Options) {
     configPaths,
   });
 
-  console.log(
-    `Loaded config from ${appConfigs.map(c => c.context).join(', ')}`,
+  // printing to stderr to not clobber stdout in case the cli command
+  // outputs structured data (e.g. as config:schema does)
+  process.stderr.write(
+    `Loaded config from ${appConfigs.map(c => c.context).join(', ')}\n`,
   );
 
   try {