From b94a2829d40257cf97615353ada8ee46c2fd2e43 Mon Sep 17 00:00:00 2001
From: WMDE-Fisch <christoph.jauera@wikimedia.de>
Date: Thu, 29 Dec 2016 15:08:54 +0100
Subject: [PATCH] Get conflict results from diff3

This patch extends the global wfMerge function to also return the
result of the first merge attempt that detects merge conflicts.

The additional output explicitly names the conflicting lines and
could help when solving edit conflicts.

Bug: T151320
Change-Id: I97acebdc87b31779200c7fde4dd4449cd1ee8ead
---
 includes/GlobalFunctions.php                  | 18 ++++++----
 .../includes/GlobalFunctions/GlobalTest.php   | 34 +++++++++++++++++--
 2 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/includes/GlobalFunctions.php b/includes/GlobalFunctions.php
index bb1951d528..1a33b76357 100644
--- a/includes/GlobalFunctions.php
+++ b/includes/GlobalFunctions.php
@@ -2404,9 +2404,10 @@ function wfShellWikiCmd( $script, array $parameters = [], array $options = [] )
  * @param string $mine
  * @param string $yours
  * @param string &$result
+ * @param string &$mergeAttemptResult
  * @return bool
  */
-function wfMerge( $old, $mine, $yours, &$result ) {
+function wfMerge( $old, $mine, $yours, &$result, &$mergeAttemptResult = null ) {
 	global $wgDiff3;
 
 	# This check may also protect against code injection in
@@ -2442,13 +2443,18 @@ function wfMerge( $old, $mine, $yours, &$result ) {
 		$oldtextName, $yourtextName );
 	$handle = popen( $cmd, 'r' );
 
-	if ( fgets( $handle, 1024 ) ) {
-		$conflict = true;
-	} else {
-		$conflict = false;
-	}
+	$mergeAttemptResult = '';
+	do {
+		$data = fread( $handle, 8192 );
+		if ( strlen( $data ) == 0 ) {
+			break;
+		}
+		$mergeAttemptResult .= $data;
+	} while ( true );
 	pclose( $handle );
 
+	$conflict = $mergeAttemptResult !== '';
+
 	# Merge differences
 	$cmd = Shell::escape( $wgDiff3, '-a', '-e', '--merge', $mytextName,
 		$oldtextName, $yourtextName );
diff --git a/tests/phpunit/includes/GlobalFunctions/GlobalTest.php b/tests/phpunit/includes/GlobalFunctions/GlobalTest.php
index 5e54b8d436..d961e415e3 100644
--- a/tests/phpunit/includes/GlobalFunctions/GlobalTest.php
+++ b/tests/phpunit/includes/GlobalFunctions/GlobalTest.php
@@ -473,26 +473,46 @@ class GlobalTest extends MediaWikiTestCase {
 		];
 	}
 
+	/**
+	 * @covers ::wfMerge
+	 */
+	public function testMerge_worksWithLessParameters() {
+		$this->markTestSkippedIfNoDiff3();
+
+		$mergedText = null;
+		$successfulMerge = wfMerge( "old1\n\nold2", "old1\n\nnew2", "new1\n\nold2", $mergedText );
+
+		$mergedText = null;
+		$conflictingMerge = wfMerge( 'old', 'old and mine', 'old and yours', $mergedText );
+
+		$this->assertEquals( true, $successfulMerge );
+		$this->assertEquals( false, $conflictingMerge );
+	}
+
 	/**
 	 * @param string $old Text as it was in the database
 	 * @param string $mine Text submitted while user was editing
 	 * @param string $yours Text submitted by the user
 	 * @param bool $expectedMergeResult Whether the merge should be a success
 	 * @param string $expectedText Text after merge has been completed
+	 * @param string $expectedMergeAttemptResult Diff3 output if conflicts occur
 	 *
 	 * @dataProvider provideMerge()
 	 * @group medium
 	 * @covers ::wfMerge
 	 */
-	public function testMerge( $old, $mine, $yours, $expectedMergeResult, $expectedText ) {
+	public function testMerge( $old, $mine, $yours, $expectedMergeResult, $expectedText,
+							   $expectedMergeAttemptResult ) {
 		$this->markTestSkippedIfNoDiff3();
 
 		$mergedText = null;
-		$isMerged = wfMerge( $old, $mine, $yours, $mergedText );
+		$attemptMergeResult = null;
+		$isMerged = wfMerge( $old, $mine, $yours, $mergedText, $mergeAttemptResult );
 
 		$msg = 'Merge should be a ';
 		$msg .= $expectedMergeResult ? 'success' : 'failure';
 		$this->assertEquals( $expectedMergeResult, $isMerged, $msg );
+		$this->assertEquals( $expectedMergeAttemptResult, $mergeAttemptResult );
 
 		if ( $isMerged ) {
 			// Verify the merged text
@@ -530,6 +550,9 @@ class GlobalTest extends MediaWikiTestCase {
 				"one one one ONE ONE\n" .
 					"\n" .
 					"two two TWO TWO\n", // note: will always end in a newline
+
+				// mergeAttemptResult:
+				"",
 			],
 
 			// #1: conflict, fail
@@ -552,6 +575,13 @@ class GlobalTest extends MediaWikiTestCase {
 
 				// result:
 				null,
+
+				// mergeAttemptResult:
+				"1,3c\n" .
+				"one one one\n" .
+				"\n" .
+				"two two\n" .
+				".\n",
 			],
 		];
 	}
-- 
2.20.1