Fix getGroupedOpcodes(0) should not have leading/trailing OP_EQ blocks

When "context" is set to 0, there should not be any OP_EQ blocks.

Signed-off-by: Jack Cherng <jfcherng@gmail.com>

Author: jfcherng

src/SequenceMatcher.php

@@ -447,6 +447,7 @@ public function getGroupedOpcodes(int $context = 3): array
         }
 
         if ($opcodes[0][0] === self::OP_EQ) {
+            // fix the leading sequence which is out of context.
             $opcodes[0] = [
                 $opcodes[0][0],
                 \max($opcodes[0][1], $opcodes[0][2] - $context),
@@ -459,6 +460,7 @@ public function getGroupedOpcodes(int $context = 3): array
         $lastItem = \count($opcodes) - 1;
         if ($opcodes[$lastItem][0] === self::OP_EQ) {
             [$tag, $i1, $i2, $j1, $j2] = $opcodes[$lastItem];
+            // fix the trailing sequence which is out of context.
             $opcodes[$lastItem] = [
                 $tag,
                 $i1,
@@ -498,6 +500,28 @@ public function getGroupedOpcodes(int $context = 3): array
             $groups[] = $group;
         }
 
+        // there will be at least leading/trailing OP_EQ blocks
+        // if we want really zero-context, we keep only non-equal blocks
+        if ($context <= 0) {
+            $groupsNew = [];
+
+            foreach ($groups as $group) {
+                $groupNew = [];
+
+                foreach ($group as $block) {
+                    if ($block[0] !== self::OP_EQ) {
+                        $groupNew[] = $block;
+                    }
+                }
+
+                if (!empty($groupNew)) {
+                    $groupsNew[] = $groupNew;
+                }
+            }
+
+            return $groupsNew;
+        }
+
         return $groups;
     }
 

tests/SequenceMatcherTest.php

@@ -39,6 +39,23 @@ public function getGroupedOpcodesDataProvider(): array
         return [
             [
                 <<<'EOT'
+A
+B
+C
+D
+EOT
+                ,
+                <<<'EOT'
+A
+B
+C
+D
+EOT
+                ,
+                [],
+            ],
+            [
+                <<<'EOT'
 apples
 oranges
 kiwis
@@ -84,6 +101,75 @@ public function testGetGroupedOpcodes(string $old, string $new, array $expected)
         static::assertSame($expected, $this->sm->getGroupedOpcodes());
     }
 
+    /**
+     * Data provider for SequenceMatcher::getGroupedOpcodes.
+     *
+     * @return array the data provider
+     */
+    public function getGroupedOpcodesWithZeroContextDataProvider(): array
+    {
+        return [
+            [
+                <<<'EOT'
+A
+B
+C
+D
+EOT
+                ,
+                <<<'EOT'
+A
+B
+C
+D
+EOT
+                ,
+                [],
+            ],
+            [
+                <<<'EOT'
+A
+B
+C
+D
+EOT
+                ,
+                <<<'EOT'
+A
+B
+X
+D
+EOT
+                ,
+                [
+                    [
+                        [SequenceMatcher::OP_REP, 2, 3, 2, 3],
+                    ],
+                ],
+            ],
+        ];
+    }
+
+    /**
+     * Test the SequenceMatcher::getGroupedOpcodes.
+     *
+     * @covers       \Jfcherng\Diff\SequenceMatcher::getGroupedOpcodes
+     * @dataProvider getGroupedOpcodesWithZeroContextDataProvider
+     *
+     * @param string $old      the old
+     * @param string $new      the new
+     * @param array  $expected the expected
+     */
+    public function testGetGroupedOpcodesWithZeroContext(string $old, string $new, array $expected): void
+    {
+        $this->sm->setSequences(
+            \explode("\n", $old),
+            \explode("\n", $new)
+        );
+
+        static::assertSame($expected, $this->sm->getGroupedOpcodes(0));
+    }
+
     /**
      * Data provider for SequenceMatcher::getOpcodes.
      *