Add exception on implicit empty config (#123)

Add exception on implicit empty config and require that an empty list be provided in order for an implicit smithy-build.json to be used.

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 {
+    smithyBuildConfigs.set(project.files())
+}

examples/jar-plugin/multi-project/consumer/smithy-build.json

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

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 `smithyBuildConfigs` property to an empty list."));
+            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/SmithyExtension.java

@@ -56,7 +56,6 @@ private void configureDefaults(Project project) {
         getFormat().convention(true);
         getAllowUnknownTraits().convention(false);
         getOutputDirectory().convention(getDefaultOutputDirectory(project));
-
     }
 
     /**

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;
@@ -57,14 +59,14 @@ 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 fail a {@link SmithyBuildTask} if an unknown trait is encountered.
      *
@@ -104,10 +106,27 @@ 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> getSmithyBuildConfigsMissing() {
+        return getSmithyBuildConfigs().map(
+                files -> !files.isEmpty() && files.filter(File::exists).isEmpty()
+        );
+    }
+
     @TaskAction
     public void execute() {
         writeHeading("Running smithy build");
 
+        if (getSmithyBuildConfigsMissing().get()) {
+            throw new GradleException("No smithy-build configs found. "
+                    + "If this was intentional, set the `smithyBuildConfigs` property to an empty list.");
+        }
+
         BuildParameterBuilder builder = new BuildParameterBuilder();
 
         // Model discovery classpath