Infers common credential helper names from target registry. (#64)

CHANGELOG.md

@@ -11,3 +11,4 @@ All notable changes to this project will be documented in this file.
 ## 0.1.1
 ### Added
 - Simple example `helloworld` project under `examples/` ([#62](https://github.com/google/jib/pull/62))
+- Infers common credential helper names (for GCR and ECR) ([#64](https://github.com/google/jib/pull/64))

README.md

@@ -41,29 +41,27 @@ Configure the plugin by changing `registry`, `repository`, and `credentialHelper
 
 #### I am using Google Container Registry (GCR)
 
-*Make sure you have the [`docker-credential-gcr` command line tool](https://cloud.google.com/container-registry/docs/advanced-authentication#docker_credential_helper).*
+*Make sure you have the [`docker-credential-gcr` command line tool](https://cloud.google.com/container-registry/docs/advanced-authentication#docker_credential_helper). Jib automatically uses `docker-credential-gcr` for obtaining credentials. To use a different credential helper, set the [`credentialHelperName`](#extended-usage) configuration.*
 
 For example, to build the image `gcr.io/my-gcp-project/my-app`, the configuration would be:
 
 ```xml
 <configuration>
   <registry>gcr.io</registry>
   <repository>my-gcp-project/my-app</repository>
-  <credentialHelperName>gcr</credentialHelperName>
 </configuration>
 ```
 
 #### I am using Amazon Elastic Container Registry (ECR)
 
-*Make sure you have the [`docker-credential-ecr-login` command line tool](https://github.com/awslabs/amazon-ecr-credential-helper).*
+*Make sure you have the [`docker-credential-ecr-login` command line tool](https://github.com/awslabs/amazon-ecr-credential-helper). Jib automatically uses `docker-credential-ecr-login` for obtaining credentials. To use a different credential helper, set the [`credentialHelperName`](#extended-usage) configuration.*
 
 For example, to build the image `aws_account_id.dkr.ecr.region.amazonaws.com/my-app`, the configuration would be:
 
 ```xml
 <configuration>
   <registry>aws_account_id.dkr.ecr.region.amazonaws.com</registry>
   <repository>my-app</repository>
-  <credentialHelperName>ecr-login</credentialHelperName>
 </configuration>
 ```
 

jib-maven-plugin/src/main/java/com/google/cloud/tools/jib/maven/BuildImageMojo.java

@@ -55,6 +55,19 @@ public class BuildImageMojo extends AbstractMojo {
   /** {@code User-Agent} header suffix to send to the registry. */
   private static final String USER_AGENT_SUFFIX = "jib-maven-plugin";
 
+  /** Attempts to infer a known credential helper name from a specified registry. */
+  @VisibleForTesting
+  @Nullable
+  static String inferCredentialHelperName(String registry) {
+    if (registry.endsWith("gcr.io")) {
+      return "gcr";
+
+    } else if (registry.endsWith("amazonaws.com")) {
+      return "ecr-login";
+    }
+    return null;
+  }
+
   @Parameter(defaultValue = "${project}", readonly = true)
   private MavenProject project;
 
@@ -101,6 +114,18 @@ public void execute() throws MojoExecutionException, MojoFailureException {
     // Parse 'from' into image reference.
     ImageReference baseImage = getImageReference();
 
+    // Infer common credential helper names if credentialHelperName is not set.
+    if (credentialHelperName == null) {
+      credentialHelperName = inferCredentialHelperName(registry);
+      if (credentialHelperName != null) {
+        getLog()
+            .info(
+                "Using docker-credential-"
+                    + credentialHelperName
+                    + " for authentication - specify a 'credentialHelperName' to override");
+      }
+    }
+
     BuildConfiguration buildConfiguration =
         BuildConfiguration.builder()
             .setBuildLogger(new MavenBuildLogger(getLog()))

jib-maven-plugin/src/test/java/com/google/cloud/tools/jib/maven/BuildImageMojoTest.java

@@ -42,6 +42,17 @@ public class BuildImageMojoTest {
 
   private final BuildImageMojo testBuildImageMojo = new BuildImageMojo();
 
+  @Test
+  public void testInferCredentialHelperName() {
+    Assert.assertEquals("gcr", BuildImageMojo.inferCredentialHelperName("gcr.io"));
+    Assert.assertEquals("gcr", BuildImageMojo.inferCredentialHelperName("asia.gcr.io"));
+    Assert.assertEquals("ecr-login", BuildImageMojo.inferCredentialHelperName("amazonaws.com"));
+    Assert.assertEquals(
+        "ecr-login",
+        BuildImageMojo.inferCredentialHelperName("aws_account_id.dkr.ecr.region.amazonaws.com"));
+    Assert.assertNull(BuildImageMojo.inferCredentialHelperName("localhost"));
+  }
+
   @Test
   public void testBuildImage_pass() throws MojoExecutionException {
     testBuildImageMojo.buildImage(mockBuildImageSteps);