Add exception on implicit empty config

examples/base-plugin/failure-cases/forbid-implicit-no-build-config/build.gradle.kts

@@ -0,0 +1,13 @@
+plugins {
+    `java-library`
+    id("software.amazon.smithy.gradle.smithy-base").version("0.10.0")
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+dependencies {
+    implementation("software.amazon.smithy:smithy-aws-traits:[1.0, 2.0[")
+}

examples/base-plugin/failure-cases/forbid-implicit-no-build-config/model/main.smithy

@@ -0,0 +1,9 @@
+namespace smithy.example
+
+structure Foo {
+    foo: String
+}
+
+@aws.auth#unsignedPayload
+operation Bar {
+}

examples/base-plugin/failure-cases/forbid-implicit-no-build-config/settings.gradle.kts

@@ -0,0 +1,8 @@
+rootProject.name = "forbid-dependency-resolution"
+
+pluginManagement {
+    repositories {
+        mavenLocal()
+        mavenCentral()
+    }
+}

examples/jar-plugin/custom-trait/consumer/build.gradle.kts

@@ -14,4 +14,8 @@ repositories {
 
 dependencies {
     implementation(project(":custom-string-trait"))
-}
+}
+
+smithy {
+    noBuildConfig.set(true)
+}

examples/jar-plugin/multi-project/consumer/build.gradle.kts

@@ -6,3 +6,7 @@ dependencies {
     implementation(project(":producer1"))
     implementation(project(":producer2"))
 }
+
+smithy {
+    noBuildConfig.set(true)
+}

examples/jar-plugin/multiple-sources/smithy-build.json

@@ -0,0 +1,3 @@
+{
+  "version": "1.0"
+}

smithy-base/src/it/java/software/amazon/smithy/gradle/ForbidImplicitNoBuildConfigTest.java

@@ -0,0 +1,24 @@
+package software.amazon.smithy.gradle;
+
+import org.gradle.testkit.runner.BuildResult;
+import org.gradle.testkit.runner.GradleRunner;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class ForbidImplicitNoBuildConfigTest {
+    @Test
+    public void testExceptionThrows() {
+        Utils.withCopy("base-plugin/failure-cases/forbid-implicit-no-build-config", buildDir -> {
+            BuildResult result = GradleRunner.create()
+                    .forwardOutput()
+                    .withProjectDir(buildDir)
+                    .withArguments("clean", "build", "--stacktrace")
+                    .buildAndFail();
+
+            Assertions.assertTrue(result.getOutput()
+                    .contains("No smithy-build configs found. If this was intentional, set the `noBuildConfigs` flag to `true`."));
+            Utils.assertArtifactsNotCreated(buildDir,
+                    "build/smithyprojections/forbid-implicit-no-build-config/source/build-info/smithy-build-info.json");
+        });
+    }
+}

smithy-base/src/main/java/software/amazon/smithy/gradle/SmithyBasePlugin.java

@@ -195,6 +195,7 @@ private TaskProvider<SmithyBuildTask> addBuildTaskForSourceSet(SourceSet sourceS
                             build.getSmithyBuildConfigs().set(extension.getSmithyBuildConfigs());
                             build.getSourceProjection().set(extension.getSourceProjection());
                             build.getProjectionSourceTags().set(extension.getProjectionSourceTags());
+                            build.getNoBuildConfig().set(extension.getNoBuildConfig());
                             build.getOutputDir().set(extension.getOutputDirectory());
 
                             // Add smithy configurations as classpaths for build task

smithy-base/src/main/java/software/amazon/smithy/gradle/SmithyExtension.java

@@ -54,6 +54,7 @@ private void configureDefaults(Project project) {
         getSourceProjection().convention(SMITHY_SOURCE_PROJECTION_DEFAULT);
         getFork().convention(false);
         getFormat().convention(true);
+        getNoBuildConfig().convention(false);
         getAllowUnknownTraits().convention(false);
         getOutputDirectory().convention(getDefaultOutputDirectory(project));
 
@@ -143,6 +144,17 @@ public NamedDomainObjectContainer<SmithySourceDirectorySet> getSourceSets() {
      */
     public abstract Property<Boolean> getFork();
 
+    /**
+     * Gets whether unknown traits in the model should be ignored.
+     *
+     * <p>By default, the build will fail if no config is provided.
+     * This can be set to true to allow the build task to execute
+     * with an empty config when no smithy-build config is provided.
+     *
+     * @return Returns true if no config should be provided.
+     */
+    public abstract Property<Boolean> getNoBuildConfig();
+
     /**
      * Gets the output directory for running Smithy build.
      *

smithy-base/src/main/java/software/amazon/smithy/gradle/tasks/SmithyBuildTask.java

@@ -10,10 +10,12 @@
 import java.util.List;
 import java.util.stream.Collectors;
 import javax.inject.Inject;
+import org.gradle.api.GradleException;
 import org.gradle.api.file.DirectoryProperty;
 import org.gradle.api.file.FileCollection;
 import org.gradle.api.model.ObjectFactory;
 import org.gradle.api.provider.Property;
+import org.gradle.api.provider.Provider;
 import org.gradle.api.provider.SetProperty;
 import org.gradle.api.tasks.Input;
 import org.gradle.api.tasks.InputFiles;
@@ -37,6 +39,7 @@ public SmithyBuildTask(ObjectFactory objectFactory) {
         super(objectFactory);
 
         getSourceProjection().convention("source");
+        getNoBuildConfig().convention(false);
         getOutputDir().convention(SmithyUtils.getProjectionOutputDirProperty(getProject()));
     }
 
@@ -57,13 +60,24 @@ public SmithyBuildTask(ObjectFactory objectFactory) {
     public abstract SetProperty<String> getProjectionSourceTags();
 
 
-    /** Smithy build configs to use for building models.
+    /**
+     * Smithy build configs to use for building models.
      *
      * @return list of smithy-build config json files
      */
     @InputFiles
     public abstract Property<FileCollection> getSmithyBuildConfigs();
 
+    /**
+     * Sets whether to allow the build to continue if no build config is set.
+     *
+     * <p> Defaults to false.
+     *
+     * @return flag indicating if build should continue if no build configs are found.
+     */
+    @Input
+    @Optional
+    public abstract Property<Boolean> getNoBuildConfig();
 
     /**
      * Sets whether to fail a {@link SmithyBuildTask} if an unknown trait is encountered.
@@ -104,9 +118,20 @@ List<String> getModelAbsolutePaths() {
                 .collect(Collectors.toList());
     }
 
+    /**
+     * Read-only property.
+     *
+     * @return Returns true if at least one of the specified build configs exists.
+     */
+    @Internal
+    Provider<Boolean> getSmithyBuildConfigsExist() {
+        return getSmithyBuildConfigs().map(files -> !files.filter(File::exists).isEmpty());
+    }
+
     @TaskAction
     public void execute() {
         writeHeading("Running smithy build");
+        validateBuildConfigs();
 
         BuildParameterBuilder builder = new BuildParameterBuilder();
 
@@ -139,4 +164,13 @@ public void execute() {
                 getFork().get()
         );
     }
+
+    private void validateBuildConfigs() {
+        // If none of the specified Smithy build configs exist and
+        // the `noBuildConfigs` flag is false then throw an error
+        if (!getSmithyBuildConfigsExist().get() && !getNoBuildConfig().get()) {
+            throw new GradleException("No smithy-build configs found. "
+                    + "If this was intentional, set the `noBuildConfigs` flag to `true`.");
+        }
+    }
 }