Treat all function signature nodes as 1-line range to avoid duplicate…

… TestLocations (#1619)

Previously, `Node` of class `ClassMethod` returned a range for the whole method. Consider the following code:

```
class Test {
    public function findMe() // line 4
    {
        // ...
    } // line 7
}
```

for this code, `ClassMethod` node returned a [4, 7] range instead of [4, 4].

Because of this, later *for each line* (4, 5, 6, 7) we found all the test cases that cover them.

If we have 1 test case `TestClass::test_method_find_me` that covers `findMe()` method, then we returned 4 exactly the same duplicate test cases for `ClassMethod` mutation, one for each of (4, 5, 6, 7) lines.

After this update, only 1 test case is returned for the function signature mutant

src/TestFramework/Coverage/LineRangeCalculator.php

@@ -36,6 +36,7 @@
 namespace Infection\TestFramework\Coverage;
 
 use Infection\PhpParser\Visitor\ParentConnector;
+use Infection\PhpParser\Visitor\ReflectionVisitor;
 use PhpParser\Node;
 
 /**
@@ -47,7 +48,11 @@ public function calculateRange(Node $node): NodeLineRangeData
     {
         $node = $this->getOuterMostArrayNode($node);
 
-        return new NodeLineRangeData($node->getStartLine(), $node->getEndLine());
+        $endLine = $node->getAttribute(ReflectionVisitor::IS_ON_FUNCTION_SIGNATURE, false) === true
+            ? $node->getStartLine() // function signature node should always be 1-line range: (start, start)
+            : $node->getEndLine();
+
+        return new NodeLineRangeData($node->getStartLine(), $endLine);
     }
 
     /**

src/TestFramework/Coverage/XmlReport/TestLocator.php

@@ -40,6 +40,7 @@
 use Infection\TestFramework\Coverage\NodeLineRangeData;
 use Infection\TestFramework\Coverage\SourceMethodLineRange;
 use Infection\TestFramework\Coverage\TestLocations;
+use Webmozart\Assert\Assert;
 
 /**
  * @internal
@@ -85,9 +86,9 @@ public function getAllTestsForMutation(
      */
     private function getTestsForFunctionSignature(NodeLineRangeData $lineRange): iterable
     {
-        foreach ($lineRange->range as $line) {
-            yield from $this->getTestsForExecutedMethodOnLine($line);
-        }
+        Assert::count($lineRange->range, 1); // 1-line range
+
+        yield from $this->getTestsForExecutedMethodOnLine($lineRange->range[0]);
     }
 
     /**

tests/phpunit/TestFramework/Coverage/LineRangeCalculatorTest.php

@@ -36,6 +36,7 @@
 namespace Infection\Tests\TestFramework\Coverage;
 
 use Infection\PhpParser\Visitor\ParentConnectorVisitor;
+use Infection\PhpParser\Visitor\ReflectionVisitor;
 use Infection\TestFramework\Coverage\LineRangeCalculator;
 use Infection\Tests\SingletonContainer;
 use PhpParser\Node;
@@ -136,6 +137,21 @@ function foo(): void
             ,
             [6],
         ];
+
+        yield 'function signature' => [
+            <<<'PHP'
+<?php
+
+class Test {
+    public function findMe() // line 4
+    {
+        // ...
+    }
+}
+PHP
+            ,
+            [4],
+        ];
     }
 
     private function createSpyTraverser()
@@ -144,10 +160,17 @@ private function createSpyTraverser()
             /**
              * @var int[]
              */
-            public $range = [];
+            public array $range = [];
 
             public function leaveNode(Node $node)
             {
+                if ($node instanceof Node\Stmt\ClassMethod && $node->name->name === 'findMe') {
+                    $node->setAttribute(ReflectionVisitor::IS_ON_FUNCTION_SIGNATURE, true);
+
+                    $lineRange = new LineRangeCalculator();
+                    $this->range = $lineRange->calculateRange($node)->range;
+                }
+
                 if ($node instanceof Node\Expr\Variable && $node->name === 'findMe') {
                     $lineRange = new LineRangeCalculator();
                     $this->range = $lineRange->calculateRange($node)->range;

tests/phpunit/TestFramework/Coverage/ProxyTraceTest.php

@@ -178,7 +178,7 @@ public function test_it_exposes_its_test_locations(): void
         $this->assertCount(
             1,
             iterator_to_array($trace->getAllTestsForMutation(
-                new NodeLineRangeData(19, 22),
+                new NodeLineRangeData(19, 19),
                 true
             ))
         );