fix: fix snippet compilation bugs

src/main/java/spoon/support/compiler/SnippetCompilationHelper.java

@@ -29,14 +29,15 @@
 import spoon.reflect.reference.CtTypeReference;
 import spoon.reflect.visitor.filter.TypeFilter;
 import spoon.support.compiler.jdt.JDTSnippetCompiler;
+import spoon.support.compiler.jdt.PositionBuilder;
 import spoon.support.reflect.declaration.CtElementImpl;
-
 import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.Arrays;
 
 /** Helper class for working with snippets */
 public class SnippetCompilationHelper {
@@ -54,11 +55,14 @@ private SnippetCompilationHelper() { }
 	 *
 	 */
 	public static void compileAndReplaceSnippetsIn(CtType<?> initialClass) {
-
 		Map<CtPath, CtElement> elements2before = new HashMap<>();
 		Map<CtPath, CtElement> elements2after = new HashMap<>();
 		for (Object o : initialClass.filterChildren(new TypeFilter<>(CtCodeSnippet.class)).list()) {
 			CtElement el = (CtElement) o;
+			if (el instanceof CtCodeSnippetStatement && containsOnlyWhiteSpace(el)) {
+				replaceComments((CtStatement) el);
+				continue;
+			}
 			elements2before.put(el.getPath(), el);
 		}
 		Factory f = initialClass.getFactory();
@@ -75,9 +79,14 @@ public static void compileAndReplaceSnippetsIn(CtType<?> initialClass) {
 		// add dummy statements for each comment so paths are same for initial and new class
 		CtType<?> clonedInitialClass = initialClass.clone();
 		addDummyStatements(clonedInitialClass);
+		removeIllegalDummyStatements(clonedInitialClass);
 
+		String pkg = initialClass.getPackage().getQualifiedName();
+		if (!pkg.equals("")) {
+			pkg = "package " + pkg + ";";
+		}
 		try {
-			build(f, "package " + initialClass.getPackage().getQualifiedName() + ";" + clonedInitialClass.toString());
+			build(f, pkg + clonedInitialClass.toString());
 		} finally {
 			// restore modifiers
 			initialClass.setModifiers(backup);
@@ -101,16 +110,67 @@ public static void compileAndReplaceSnippetsIn(CtType<?> initialClass) {
 		}
 	}
 
+	private static boolean containsOnlyWhiteSpace(CtElement element) {
+		char[] snippet = (element.toString() + '\n').toCharArray();
+		int next = PositionBuilder.findNextNonWhitespace(snippet, snippet.length - 1, 0);
+		if (next == -1) {
+			return true;
+		} else {
+			return false;
+		}
+	}
+
+	private static void replaceComments(CtStatement element) {
+		replaceComments(element, (element.toString() + '\n').toCharArray());
+		element.delete();
+	}
+
+	private static void replaceComments(CtStatement element, char[] snippet) {
+		Factory factory = element.getFactory();
+		CtComment comment;
+		for (int i = 0; i < snippet.length; i++) {
+			if (Character.isWhitespace(snippet[i])) {
+				continue;
+			}
+			int end = PositionBuilder.getEndOfComment(snippet, snippet.length - 1, i);
+			if (snippet[i + 1] == '*') {
+				comment = factory.createComment(new String(Arrays.copyOfRange(snippet, i + 2, end - 1)), CtComment.CommentType.BLOCK);
+			} else {
+				comment = factory.createComment(new String(Arrays.copyOfRange(snippet, i + 2, end)), CtComment.CommentType.INLINE);
+			}
+			element.insertBefore(comment);
+			if (end + 1 < snippet.length) {
+				replaceComments(element, Arrays.copyOfRange(snippet, end + 1, snippet.length));
+			}
+			break;
+		}
+	}
+
 	private static void addDummyStatements(CtType<?> clonedInitialClass) {
 		Factory factory = clonedInitialClass.getFactory();
-		CtConstructorCall call = factory.createConstructorCall(factory.createCtTypeReference(Object.class));
 		List<CtComment> list = clonedInitialClass.filterChildren(new TypeFilter<>(CtComment.class)).list();
 		for (CtComment comment : list) {
+			CtConstructorCall call = factory.createConstructorCall(factory.createCtTypeReference(Object.class));
 			comment.insertBefore(call);
 			comment.delete();
 		}
 	}
 
+	private static void removeIllegalDummyStatements(CtType<?> clonedInitialClass) {
+		for (Object o : clonedInitialClass.filterChildren(new TypeFilter<>(CtReturn.class)).list()) {
+			CtStatement returnStmt = (CtStatement) o;
+			CtBlock block = (CtBlock) returnStmt.getParent();
+			for (int i = block.getStatements().size() - 1; i > 0; i--) {
+				CtStatement currentStatement = block.getStatement(i);
+				if (currentStatement == returnStmt) {
+					break;
+				} else {
+					currentStatement.delete();
+				}
+			}
+		}
+	}
+
 	public static CtStatement compileStatement(CtCodeSnippetStatement st)
 			throws SnippetCompilationError {
 		return internalCompileStatement(st, st.getFactory().Type().VOID_PRIMITIVE);

src/main/java/spoon/support/compiler/jdt/PositionBuilder.java

@@ -662,13 +662,15 @@ static int findNextChar(char[] contents, int maxOff, int off, char expectedChar)
 	}
 
 	/**
-	 * @param maxOff maximum acceptable return value
+	 * @param content the character array on which the search will be performed.
+	 * @param maxOff maximum acceptable return value.
+	 * @param off the offset of {@code content} where the search begins.
 	 * @return index of first non whitespace char, searching forward.
 	 * Can return 'off' if it is non whitespace.
 	 * Note: all kinds of java comments are understood as whitespace too.
 	 * The search must start out of comment or on the first character of the comment
 	 */
-	static int findNextNonWhitespace(char[] content, int maxOff, int off) {
+	public static int findNextNonWhitespace(char[] content, int maxOff, int off) {
 		return findNextNonWhitespace(true, content, maxOff, off);
 	}
 
@@ -775,11 +777,13 @@ static int findPrevWhitespace(char[] content, int minOff, int off) {
 		return -1;
 	}
 	/**
-	 * @param maxOff maximum acceptable return value
+	 * @param content the character array on which the search will be performed.
+	 * @param maxOff maximum acceptable return value.
+	 * @param off the offset of {@code content} where the search begins.
 	 * @return if the off points at start of comment then it returns offset which points on last character of the comment
 	 * if the off does not point at start of comment then it returns -1
 	 */
-	static int getEndOfComment(char[] content, int maxOff, int off) {
+	public static int getEndOfComment(char[] content, int maxOff, int off) {
 		maxOff = Math.min(maxOff, content.length - 1);
 		if (off + 1 <= maxOff) {
 			if (content[off] == '/' && content[off + 1] == '*') {

src/test/java/spoon/test/snippets/SnippetTest.java

@@ -181,9 +181,7 @@ public void testCompileSnippetsWithCtComment() {
 		CtBlock innerBlock = body.getStatement(0);
 		innerBlock.addStatement(0,factory.createCodeSnippetStatement("invokedMethod()"));
 		body.addStatement(0,factory.createComment("block comment", CtComment.CommentType.BLOCK));
-
 		testClass.compileAndReplaceSnippets();
-
 		assertTrue(body.getStatements().get(0) instanceof CtComment);
 		assertTrue(body.getStatements().get(1) instanceof CtBlock);
 		assertTrue(body.getStatements().get(2) instanceof CtComment);
@@ -197,4 +195,48 @@ public void testCompileSnippetsWithCtComment() {
 		assertEquals(0,body.getStatements().get(2).getComments().size());
 		assertEquals(0,body.getStatements().get(3).getComments().size());
 	}
+
+	@Test
+	public void testCommentSnippetCompilation() {
+		// contract: a snippet with only comments should be replaced with corresponding CtComments
+		Launcher launcher = new Launcher();
+		Factory factory = launcher.getFactory();
+		launcher.addInputResource("src/test/resources/snippet/SnippetCommentResource.java");
+		launcher.buildModel();
+		CtClass<?> snippetClass = factory.Class().get("snippet.test.resources.SnippetCommentResource");
+		CtMethod method = snippetClass.getMethodsByName("methodForCommentOnlySnippet").get(0);
+		CtBlock body = method.getBody();
+		body.addStatement(1,factory.createCodeSnippetStatement("/* a \n block \n comment */\n// inline"));
+		body.addStatement(0,factory.createCodeSnippetStatement("/* a \n block \n comment */"));
+		body.addStatement(0,factory.createCodeSnippetStatement("int x"));
+		body.addStatement(0,factory.createCodeSnippetStatement("  // inline"));
+		snippetClass.compileAndReplaceSnippets();
+		assertTrue(body.getStatements().get(0) instanceof CtComment);
+		assertTrue(body.getStatements().get(1) instanceof CtLocalVariable);
+		assertTrue(body.getStatements().get(2) instanceof CtComment);
+		assertTrue(body.getStatements().get(3) instanceof CtReturn);
+		assertTrue(body.getStatements().get(4) instanceof CtComment);
+		assertTrue(body.getStatements().get(5) instanceof CtComment);
+		assertEquals(CtComment.CommentType.INLINE,((CtComment) body.getStatements().get(0)).getCommentType());
+		assertEquals(CtComment.CommentType.BLOCK,((CtComment) body.getStatements().get(2)).getCommentType());
+		assertEquals(CtComment.CommentType.BLOCK,((CtComment) body.getStatements().get(4)).getCommentType());
+		assertEquals(CtComment.CommentType.INLINE,((CtComment) body.getStatements().get(5)).getCommentType());
+		assertEquals(6,body.getStatements().size());
+	}
+
+	@Test
+	public void testSnippetCompilationInUnnamedPackage() {
+		// contract: a snippet can be successfully compiled in a class with an unnamed package
+		Launcher launcher = new Launcher();
+		Factory factory = launcher.getFactory();
+		launcher.addInputResource("src/test/resources/snippet/UnnamedPackageSnippetResource.java");
+		launcher.buildModel();
+		CtClass<?> snippetClass = factory.Class().get("UnnamedPackageSnippetResource");
+		CtMethod method = snippetClass.getMethodsByName("method").get(0);
+		CtBlock body = method.getBody();
+		body.addStatement(0,factory.createCodeSnippetStatement("int x"));
+		snippetClass.compileAndReplaceSnippets();
+		assertTrue(body.getStatements().get(0) instanceof CtLocalVariable);
+		assertEquals(1,body.getStatements().size()); 
+	}
 }

src/test/resources/snippet/SnippetCommentResource.java

@@ -10,4 +10,8 @@ public void modifiedMethod() {
 
     void invokedMethod() {
     }
+
+    public void methodForCommentOnlySnippet(){
+        return;
+    }
 }

src/test/resources/snippet/UnnamedPackageSnippetResource.java

@@ -0,0 +1,6 @@
+public class UnnamedPackageSnippetResource {
+
+    public void method() {
+
+    }
+}