Make snippet directory resolution more robust

The previous approach had (at least) two problems:

 - A Gradle build run from a directory that also contains a pom.xml
   would result in the resolver incorrectly identifing that Maven was
   being used
 - A Maven build run from a directory that did not could a pom and
   that used -f to provide the path to a pom would result in the
   resolver incorretly indentifying that Gradle was being used

With this commit, the resolver now uses the presence of the maven.home
system property to identify that Maven is being used. When Maven
is being used, rather than looking for a pom.xml in the working
directory, the resolver now locates the pom.xml by searching up the
directory hierarchy from the docdir.

Closes gh-297

spring-restdocs-asciidoctor/src/main/java/org/springframework/restdocs/asciidoctor/DefaultAttributesPreprocessor.java

@@ -16,8 +16,6 @@
 
 package org.springframework.restdocs.asciidoctor;
 
-import java.io.File;
-
 import org.asciidoctor.ast.Document;
 import org.asciidoctor.extension.Preprocessor;
 import org.asciidoctor.extension.PreprocessorReader;
@@ -30,8 +28,7 @@ import org.asciidoctor.extension.PreprocessorReader;
  */
 final class DefaultAttributesPreprocessor extends Preprocessor {
 
-	private final SnippetsDirectoryResolver snippetsDirectoryResolver = new SnippetsDirectoryResolver(
-			new File("."));
+	private final SnippetsDirectoryResolver snippetsDirectoryResolver = new SnippetsDirectoryResolver();
 
 	@Override
 	public PreprocessorReader process(Document document, PreprocessorReader reader) {

spring-restdocs-asciidoctor/src/main/java/org/springframework/restdocs/asciidoctor/SnippetsDirectoryResolver.java

@@ -17,6 +17,7 @@
 package org.springframework.restdocs.asciidoctor;
 
 import java.io.File;
+import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.Map;
@@ -30,29 +31,42 @@ import java.util.Map;
  */
 class SnippetsDirectoryResolver {
 
-	private final File root;
-
-	SnippetsDirectoryResolver(File root) {
-		this.root = root;
-	}
-
 	File getSnippetsDirectory(Map<String, Object> attributes) {
-		if (new File(this.root, "pom.xml").exists()) {
+		if (System.getProperty("maven.home") != null) {
 			return getMavenSnippetsDirectory(attributes);
 		}
 		return getGradleSnippetsDirectory(attributes);
 	}
 
 	private File getMavenSnippetsDirectory(Map<String, Object> attributes) {
-		Path rootPath = Paths.get(this.root.getAbsolutePath());
-		Path docDirPath = Paths.get((String) attributes.get("docdir"));
-		Path relativePath = docDirPath.relativize(rootPath);
-		return new File(relativePath.toFile(), "target/generated-snippets");
+		Path docdir = Paths.get(getRequiredAttribute(attributes, "docdir"));
+		return new File(docdir.relativize(findPom(docdir).getParent()).toFile(),
+				"target/generated-snippets");
+	}
+
+	private Path findPom(Path docdir) {
+		Path path = docdir;
+		while (path != null) {
+			Path pom = path.resolve("pom.xml");
+			if (Files.isRegularFile(pom)) {
+				return pom;
+			}
+			path = path.getParent();
+		}
+		throw new IllegalStateException("pom.xml not found in '" + docdir + "' or above");
 	}
 
 	private File getGradleSnippetsDirectory(Map<String, Object> attributes) {
-		return new File((String) attributes.get("projectdir"),
+		return new File(getRequiredAttribute(attributes, "projectdir"),
 				"build/generated-snippets");
 	}
 
+	private String getRequiredAttribute(Map<String, Object> attributes, String name) {
+		String attribute = (String) attributes.get(name);
+		if (attribute == null || attribute.length() == 0) {
+			throw new IllegalStateException(name + " attribute not found");
+		}
+		return attribute;
+	}
+
 }

spring-restdocs-asciidoctor/src/test/java/org/springframework/restdocs/asciidoctor/DefaultAttributesPreprocessorTests.java

@@ -35,8 +35,9 @@ public class DefaultAttributesPreprocessorTests {
 
 	@Test
 	public void snippetsAttributeIsSet() {
-		String converted = Asciidoctor.Factory.create().convert("{snippets}",
-				new Options());
+		Options options = new Options();
+		options.setAttributes(new Attributes("projectdir=../../.."));
+		String converted = Asciidoctor.Factory.create().convert("{snippets}", options);
 		assertThat(converted,
 				containsString("build" + File.separatorChar + "generated-snippets"));
 	}
@@ -44,7 +45,7 @@ public class DefaultAttributesPreprocessorTests {
 	@Test
 	public void snippetsAttributeFromConvertArgumentIsNotOverridden() {
 		Options options = new Options();
-		options.setAttributes(new Attributes("snippets=custom"));
+		options.setAttributes(new Attributes("snippets=custom projectdir=../../.."));
 		String converted = Asciidoctor.Factory.create().convert("{snippets}", options);
 		assertThat(converted, containsString("custom"));
 	}
@@ -52,7 +53,7 @@ public class DefaultAttributesPreprocessorTests {
 	@Test
 	public void snippetsAttributeFromDocumentPreambleIsNotOverridden() {
 		Options options = new Options();
-		options.setAttributes(new Attributes("snippets=custom"));
+		options.setAttributes(new Attributes("projectdir=../../.."));
 		String converted = Asciidoctor.Factory.create()
 				.convert(":snippets: custom\n{snippets}", options);
 		assertThat(converted, containsString("custom"));

spring-restdocs-asciidoctor/src/test/java/org/springframework/restdocs/asciidoctor/SnippetsDirectoryResolverTests.java

@@ -23,6 +23,7 @@ import java.util.Map;
 
 import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.junit.rules.TemporaryFolder;
 
 import static org.hamcrest.CoreMatchers.equalTo;
@@ -39,30 +40,72 @@ public class SnippetsDirectoryResolverTests {
 	@Rule
 	public TemporaryFolder temporaryFolder = new TemporaryFolder();
 
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
 	@Test
-	public void mavenProjectsUseTargetGeneratedSnippetsRelativeToDocDir()
+	public void mavenProjectsUseTargetGeneratedSnippetsRelativeToDocdir()
 			throws IOException {
 		this.temporaryFolder.newFile("pom.xml");
 		Map<String, Object> attributes = new HashMap<>();
 		attributes.put("docdir",
 				new File(this.temporaryFolder.getRoot(), "src/main/asciidoc")
 						.getAbsolutePath());
-		File snippetsDirectory = new SnippetsDirectoryResolver(
-				this.temporaryFolder.getRoot()).getSnippetsDirectory(attributes);
+		File snippetsDirectory = getMavenSnippetsDirectory(attributes);
 		assertThat(snippetsDirectory.isAbsolute(), is(false));
 		assertThat(snippetsDirectory,
 				equalTo(new File("../../../target/generated-snippets")));
 	}
 
+	@Test
+	public void illegalStateExceptionWhenMavenPomCannotBeFound() throws IOException {
+		Map<String, Object> attributes = new HashMap<>();
+		String docdir = new File(this.temporaryFolder.getRoot(), "src/main/asciidoc")
+				.getAbsolutePath();
+		attributes.put("docdir", docdir);
+		this.thrown.expect(IllegalStateException.class);
+		this.thrown
+				.expectMessage(equalTo("pom.xml not found in '" + docdir + "' or above"));
+		getMavenSnippetsDirectory(attributes);
+	}
+
+	@Test
+	public void illegalStateWhenDocdirAttributeIsNotSetInMavenProject()
+			throws IOException {
+		Map<String, Object> attributes = new HashMap<>();
+		this.thrown.expect(IllegalStateException.class);
+		this.thrown.expectMessage(equalTo("docdir attribute not found"));
+		getMavenSnippetsDirectory(attributes);
+	}
+
 	@Test
 	public void gradleProjectsUseBuildGeneratedSnippetsBeneathProjectDir()
 			throws IOException {
 		Map<String, Object> attributes = new HashMap<>();
 		attributes.put("projectdir", "project/dir");
-		File snippetsDirectory = new SnippetsDirectoryResolver(
-				this.temporaryFolder.getRoot()).getSnippetsDirectory(attributes);
+		File snippetsDirectory = new SnippetsDirectoryResolver()
+				.getSnippetsDirectory(attributes);
 		assertThat(snippetsDirectory,
 				equalTo(new File("project/dir/build/generated-snippets")));
 	}
 
+	@Test
+	public void illegalStateWhenProjectdirAttributeIsNotSetInGradleProject()
+			throws IOException {
+		Map<String, Object> attributes = new HashMap<>();
+		this.thrown.expect(IllegalStateException.class);
+		this.thrown.expectMessage(equalTo("projectdir attribute not found"));
+		new SnippetsDirectoryResolver().getSnippetsDirectory(attributes);
+	}
+
+	private File getMavenSnippetsDirectory(Map<String, Object> attributes) {
+		System.setProperty("maven.home", "/maven/home");
+		try {
+			return new SnippetsDirectoryResolver().getSnippetsDirectory(attributes);
+		}
+		finally {
+			System.clearProperty("maven.home");
+		}
+	}
+
 }