[fix] Fix false positive conflict in line-based merge on pure addition

src/main/java/se/kth/spork/util/LineBasedMerge.java

@@ -31,6 +31,12 @@ public class LineBasedMerge {
      * @return A pair containing the merge and the amount of conflicts.
      */
     public static Pair<String, Integer> merge(String base, String left, String right) {
+        if (base.isEmpty() && (left.isEmpty() || right.isEmpty())) {
+            // For some reason, this merge implementation reports a conflict on pure additions.
+            // This is an easy fix for that. See #144 for details.
+            return Pair.of(left.isEmpty() ? right : left, 0);
+        }
+
         RawText baseRaw = new RawText(base.getBytes());
         RawText leftRaw = new RawText(left.getBytes());
         RawText rightRaw = new RawText(right.getBytes());

src/test/java/se/kth/spork/cli/CliTest.java

@@ -132,6 +132,8 @@ private static void runTestMerge(Util.TestSources sources, Path tempDir) throws
 
         Object expectedImports = mergeTree.getMetadata(Parser.IMPORT_STATEMENTS);
         assert expectedImports != null;
+        Object expectedCuComment = mergeTree.getMetadata(Parser.COMPILATION_UNIT_COMMENT);
+        assert expectedCuComment != null;
 
         String expectedPrettyPrint = Cli.prettyPrint(mergeTree);
 
@@ -140,12 +142,14 @@ private static void runTestMerge(Util.TestSources sources, Path tempDir) throws
 
         CtModule reParsedMerge = Parser.parse(outFile);
         Object reParsedImports = reParsedMerge.getMetadata(Parser.IMPORT_STATEMENTS);
+        Object reparsedCuComment = reParsedMerge.getMetadata(Parser.COMPILATION_UNIT_COMMENT);
 
         System.out.println(Cli.prettyPrint(mergeTree));
         assertEquals(Cli.prettyPrint(mergeTree), expectedPrettyPrint);
 
         assertEquals(mergeTree, reParsedMerge);
 
         assertEquals(reParsedImports, expectedImports);
+        assertEquals(reparsedCuComment, expectedCuComment);
     }
 }

src/test/resources/clean/both_modified/add_file_header/Base.java

@@ -0,0 +1,7 @@
+package se.kth.spork;
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("Hello, world!");
+    }
+}

src/test/resources/clean/both_modified/add_file_header/Expected.java

@@ -0,0 +1,33 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020, Simon Larsén
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package se.kth.spork;
+
+/**
+ * This is the main class :)
+ */
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("Hello, world!");
+    }
+}

src/test/resources/clean/both_modified/add_file_header/Left.java

@@ -0,0 +1,10 @@
+package se.kth.spork;
+
+/**
+ * This is the main class :)
+ */
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("Hello, world!");
+    }
+}

src/test/resources/clean/both_modified/add_file_header/Right.java

@@ -0,0 +1,30 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2020, Simon Larsén
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package se.kth.spork;
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("Hello, world!");
+    }
+}