Enable strict validation of dependencies

Previously, if one invokes the service asking for dependency `foo` and
`foo` does not exist we created a starter for it, that is
`spring-boot-starter-foo`. This mechanism was put in place because we
don't know all starters and to offer a nice fallback for users who know
what they're doing.

That statement proved to be wrong since users actually discover new
starters via the service and don't seem to attempt to create such starter
that are located in the `org.springframework.boot` groupId anyway. Most
if not all of those are pilot errors.

This commit enables strict validation of dependencies and generate an
appropriate exception if it isn't defined in the meta-data.

Closes gh-234

initializr-web/src/main/groovy/io/spring/initializr/web/project/AbstractInitializrController.groovy

@@ -17,6 +17,7 @@
 package io.spring.initializr.web.project
 
 import javax.annotation.PostConstruct
+import javax.servlet.http.HttpServletResponse
 
 import io.spring.initializr.generator.InvalidProjectRequestException
 import io.spring.initializr.metadata.InitializrMetadataProvider
@@ -24,7 +25,6 @@ import io.spring.initializr.metadata.InitializrMetadataProvider
 import org.springframework.beans.factory.annotation.Autowired
 import org.springframework.http.HttpStatus
 import org.springframework.web.bind.annotation.ExceptionHandler
-import org.springframework.web.bind.annotation.ResponseStatus
 import org.springframework.web.servlet.support.ServletUriComponentsBuilder
 
 import static io.spring.initializr.util.GroovyTemplate.template
@@ -47,10 +47,9 @@ abstract class AbstractInitializrController {
 		forceSsl = metadataProvider.get().configuration.env.forceSsl
 	}
 
-	@ExceptionHandler(InvalidProjectRequestException)
-	@ResponseStatus(value= HttpStatus.BAD_REQUEST)
-	public void invalidProjectVersion() {
-		// Nothing to do
+	@ExceptionHandler
+	public void invalidProjectRequest(HttpServletResponse response, InvalidProjectRequestException ex) {
+		response.sendError(HttpStatus.BAD_REQUEST.value(), ex.getMessage());
 	}
 
 	/**

initializr-web/src/test/groovy/io/spring/initializr/web/project/MainControllerIntegrationTests.groovy

@@ -16,10 +16,10 @@
 
 package io.spring.initializr.web.project
 
+import groovy.json.JsonSlurper
 import io.spring.initializr.metadata.Dependency
 import io.spring.initializr.web.AbstractInitializrControllerIntegrationTests
 import io.spring.initializr.web.mapper.InitializrMetadataVersion
-import io.spring.initializr.web.project.MainController
 import org.json.JSONObject
 import org.junit.Ignore
 import org.junit.Test
@@ -41,6 +41,7 @@ import static org.junit.Assert.assertFalse
 import static org.junit.Assert.assertNotNull
 import static org.junit.Assert.assertThat
 import static org.junit.Assert.assertTrue
+import static org.junit.Assert.fail
 
 /**
  * @author Stephane Nicoll
@@ -326,15 +327,24 @@ class MainControllerIntegrationTests extends AbstractInitializrControllerIntegra
 	void missingDependencyProperException() {
 		try {
 			downloadArchive('/starter.zip?style=foo:bar')
+			fail("Should have failed")
 		} catch (HttpClientErrorException ex) {
 			assertEquals HttpStatus.BAD_REQUEST, ex.getStatusCode()
+			assertStandardErrorBody(ex.getResponseBodyAsString(),
+					"Unknown dependency 'foo:bar' check project metadata")
 		}
-
 	}
 
 	@Test
-	void downloadWithUnknownSpringBootStarter() { // Simple id are accepted as spring-boot-starter
-		downloadZip('/starter.zip?style=foo').pomAssert().hasSpringBootStarterDependency('foo')
+	void invalidDependencyProperException() {
+		try {
+			downloadArchive('/starter.zip?style=foo')
+			fail("Should have failed")
+		} catch (HttpClientErrorException ex) {
+			assertEquals HttpStatus.BAD_REQUEST, ex.getStatusCode()
+			assertStandardErrorBody(ex.getResponseBodyAsString(),
+					"Unknown dependency 'foo' check project metadata")
+		}
 	}
 
 	@Test
@@ -412,5 +422,10 @@ class MainControllerIntegrationTests extends AbstractInitializrControllerIntegra
 		return new JSONObject(json)
 	}
 
+	private static void assertStandardErrorBody(String body, String message) {
+		assertNotNull "error body must be available", body
+		def model = new JsonSlurper().parseText(body)
+		assertEquals message, model.message
+	}
 
 }