feat(codepipeline): add ability to override env variables in CodeBuild actions (#4502)

Previously, environment variables were always defined on the CodeBuild project level,
which made it difficult to re-use the same project in the pipeline.
Now, you can specify environment variables on the CodeBuild action level,
which will override any project-level settings.

Fixes #4531

Author: skinny85

packages/@aws-cdk/aws-codebuild/lib/project.ts

@@ -617,6 +617,23 @@ export class Project extends ProjectBase {
     return new Import(scope, id);
   }
 
+  /**
+   * Convert the environment variables map of string to {@link BuildEnvironmentVariable},
+   * which is the customer-facing type, to a list of {@link CfnProject.EnvironmentVariableProperty},
+   * which is the representation of environment variables in CloudFormation.
+   *
+   * @param environmentVariables the map of string to environment variables
+   * @returns an array of {@link CfnProject.EnvironmentVariableProperty} instances
+   */
+  public static serializeEnvVariables(environmentVariables: { [name: string]: BuildEnvironmentVariable }):
+      CfnProject.EnvironmentVariableProperty[] {
+    return Object.keys(environmentVariables).map(name => ({
+      name,
+      type: environmentVariables[name].type || BuildEnvironmentVariableType.PLAINTEXT,
+      value: environmentVariables[name].value,
+    }));
+  }
+
   public readonly grantPrincipal: iam.IPrincipal;
 
   /**
@@ -870,11 +887,7 @@ export class Project extends ProjectBase {
         : undefined,
       privilegedMode: env.privileged || false,
       computeType: env.computeType || this.buildImage.defaultComputeType,
-      environmentVariables: !hasEnvironmentVars ? undefined : Object.keys(vars).map(name => ({
-        name,
-        type: vars[name].type || BuildEnvironmentVariableType.PLAINTEXT,
-        value: vars[name].value
-      }))
+      environmentVariables: hasEnvironmentVars ? Project.serializeEnvVariables(vars) : undefined,
     };
   }
 

packages/@aws-cdk/aws-codepipeline-actions/lib/codebuild/build-action.ts

@@ -60,6 +60,15 @@ export interface CodeBuildActionProps extends codepipeline.CommonAwsActionProps
    * @default CodeBuildActionType.BUILD
    */
   readonly type?: CodeBuildActionType;
+
+  /**
+   * The environment variables to pass to the CodeBuild project when this action executes.
+   * If a variable with the same name was set both on the project level, and here,
+   * this value will take precedence.
+   *
+   * @default - No additional environment variables are specified.
+   */
+  readonly environmentVariables?: { [name: string]: codebuild.BuildEnvironmentVariable };
 }
 
 /**
@@ -125,6 +134,8 @@ export class CodeBuildAction extends Action {
 
     const configuration: any = {
       ProjectName: this.props.project.projectName,
+      EnvironmentVariables: this.props.environmentVariables &&
+        cdk.Stack.of(scope).toJsonString(codebuild.Project.serializeEnvVariables(this.props.environmentVariables)),
     };
     if ((this.actionProperties.inputs || []).length > 1) {
       // lazy, because the Artifact name might be generated lazily

packages/@aws-cdk/aws-codepipeline-actions/test/integ.pipeline-code-commit-build.expected.json

@@ -578,7 +578,8 @@
                 "Configuration": {
                   "ProjectName": {
                     "Ref": "MyBuildProject30DB9D6E"
-                  }
+                  },
+                  "EnvironmentVariables": "[{\"name\":\"TEST_ENV_VARIABLE\",\"type\":\"PLAINTEXT\",\"value\":\"test env variable value\"},{\"name\":\"PARAM_STORE_VARIABLE\",\"type\":\"PARAMETER_STORE\",\"value\":\"param_store\"}]"
                 },
                 "InputArtifacts": [
                   {

packages/@aws-cdk/aws-codepipeline-actions/test/integ.pipeline-code-commit-build.ts

@@ -4,6 +4,8 @@ import codepipeline = require('@aws-cdk/aws-codepipeline');
 import cdk = require('@aws-cdk/core');
 import cpactions = require('../lib');
 
+// tslint:disable:object-literal-key-quotes
+
 const app = new cdk.App();
 
 const stack = new cdk.Stack(app, 'aws-cdk-codepipeline-codecommit-codebuild');
@@ -25,6 +27,15 @@ const buildAction = new cpactions.CodeBuildAction({
   project,
   input: sourceOutput,
   outputs: [new codepipeline.Artifact()],
+  environmentVariables: {
+    'TEST_ENV_VARIABLE': {
+      value: 'test env variable value',
+    },
+    'PARAM_STORE_VARIABLE': {
+      value: 'param_store',
+      type: codebuild.BuildEnvironmentVariableType.PARAMETER_STORE,
+    },
+  },
 });
 const testAction = new cpactions.CodeBuildAction({
   type: cpactions.CodeBuildActionType.TEST,