feat(cli): added build field to cdk.json

packages/aws-cdk/README.md

@@ -464,6 +464,7 @@ Some of the interesting keys that can be used in the JSON configuration files:
 ```json5
 {
     "app": "node bin/main.js",        // Command to start the CDK app      (--app='node bin/main.js')
+    "build": "mvn package",           // Specify pre-synth build           (no command line option)
     "context": {                      // Context entries                   (--context=key=value)
         "key": "value"
     },
@@ -473,6 +474,12 @@ Some of the interesting keys that can be used in the JSON configuration files:
 }
 ```
 
+If specified, the command in the `build` key will be executed immediately before synthesis.
+This can be used to build Lambda Functions, CDK Application code, or other assets. 
+`build` cannot be specified on the command line or in the User configuration, 
+and must be specified in the Project configuration. The command specified
+in `build` will be executed by the "watch" process before deployment.
+
 ### Environment
 
 The following environment variables affect aws-cdk:

packages/aws-cdk/lib/api/cxapp/exec.ts

@@ -46,6 +46,11 @@ export async function execProgram(aws: SdkProvider, config: Configuration): Prom
   debug('context:', context);
   env[cxapi.CONTEXT_ENV] = JSON.stringify(context);
 
+  const build = config.settings.get(['build']);
+  if (build) {
+    await exec(commandToArray(build));
+  }
+
   const app = config.settings.get(['app']);
   if (!app) {
     throw new Error(`--app is required either in command-line, in ${PROJECT_CONFIG} or in ${USER_DEFAULTS}`);
@@ -57,7 +62,7 @@ export async function execProgram(aws: SdkProvider, config: Configuration): Prom
     return createAssembly(app);
   }
 
-  const commandLine = await guessExecutable(appToArray(app));
+  const commandLine = await guessExecutable(commandToArray(app));
 
   const outdir = config.settings.get(['output']);
   if (!outdir) {
@@ -74,7 +79,7 @@ export async function execProgram(aws: SdkProvider, config: Configuration): Prom
 
   debug('env:', env);
 
-  await exec();
+  await exec(commandLine);
 
   return createAssembly(outdir);
 
@@ -91,7 +96,7 @@ export async function execProgram(aws: SdkProvider, config: Configuration): Prom
     }
   }
 
-  async function exec() {
+  async function exec(commandAndArgs: string[]) {
     return new Promise<void>((ok, fail) => {
       // We use a slightly lower-level interface to:
       //
@@ -103,7 +108,9 @@ export async function execProgram(aws: SdkProvider, config: Configuration): Prom
       //   anyway, and if the subprocess is printing to it for debugging purposes the
       //   user gets to see it sooner. Plus, capturing doesn't interact nicely with some
       //   processes like Maven.
-      const proc = childProcess.spawn(commandLine[0], commandLine.slice(1), {
+      const command = commandAndArgs[0];
+      const args = commandAndArgs.slice(1);
+      const proc = childProcess.spawn(command, args, {
         stdio: ['ignore', 'inherit', 'inherit'],
         detached: false,
         shell: true,
@@ -150,12 +157,12 @@ async function populateDefaultEnvironmentIfNeeded(aws: SdkProvider, env: { [key:
 }
 
 /**
- * Make sure the 'app' is an array
+ * Make sure the 'command' is an array
  *
  * If it's a string, split on spaces as a trivial way of tokenizing the command line.
  */
-function appToArray(app: any) {
-  return typeof app === 'string' ? app.split(' ') : app;
+function commandToArray(command: any) {
+  return typeof command === 'string' ? command.split(' ') : command;
 }
 
 type CommandGenerator = (file: string) => string[];

packages/aws-cdk/lib/settings.ts

@@ -113,6 +113,10 @@ export class Configuration {
 
     const readUserContext = this.props.readUserContext ?? true;
 
+    if (userConfig.get(['build'])) {
+      throw new Error('The `build` key cannot be specified in the user config (~/.cdk.json), specify it in the project config (cdk.json) instead');
+    }
+
     const contextSources = [
       this.commandLineContext,
       this.projectConfig.subSettings([CONTEXT_KEY]).makeReadOnly(),

packages/aws-cdk/test/api/exec.test.ts

@@ -194,6 +194,36 @@ test('application set in --app is `*.js` and executable', async () => {
   await execProgram(sdkProvider, config);
 });
 
+test('cli throws when the `build` script fails', async () => {
+  // GIVEN
+  config.settings.set(['build'], 'fake-command');
+  mockSpawn({
+    commandLine: ['fake-command'],
+    exitCode: 127,
+  });
+
+  // WHEN
+  await expect(execProgram(sdkProvider, config)).rejects.toEqual(new Error('Subprocess exited with error 127'));
+}, TEN_SECOND_TIMEOUT);
+
+test('cli does not throw when the `build` script succeeds', async () => {
+  // GIVEN
+  config.settings.set(['build'], 'real command');
+  config.settings.set(['app'], 'executable-app.js');
+  mockSpawn({
+    commandLine: ['real', 'command'], // `build` key is split on whitespace
+    exitCode: 0,
+  },
+  {
+    commandLine: ['executable-app.js'],
+    sideEffect: () => writeOutputAssembly(),
+  });
+
+  // WHEN
+  await execProgram(sdkProvider, config);
+}, TEN_SECOND_TIMEOUT);
+
+
 function writeOutputAssembly() {
   const asm = testAssembly({
     stacks: [],

packages/aws-cdk/test/usersettings.test.ts

@@ -69,4 +69,24 @@ test('load context from all 3 files if available', async () => {
   expect(config.context.get('project')).toBe('foobar');
   expect(config.context.get('foo')).toBe('bar');
   expect(config.context.get('test')).toBe('bar');
+});
+
+test('throws an error if the `build` key is specified in the user config', async () => {
+  // GIVEN
+  const GIVEN_CONFIG: Map<string, any> = new Map([
+    [USER_CONFIG, {
+      build: 'foobar',
+    }],
+  ]);
+
+  // WHEN
+  mockedFs.pathExists.mockImplementation(path => {
+    return GIVEN_CONFIG.has(path);
+  });
+  mockedFs.readJSON.mockImplementation(path => {
+    return GIVEN_CONFIG.get(path);
+  });
+
+  // THEN
+  await expect(new Configuration().load()).rejects.toEqual(new Error('The `build` key cannot be specified in the user config (~/.cdk.json), specify it in the project config (cdk.json) instead'));
 });