From 3b3a16db765741502b86fa4ee4f60834684aa665 Mon Sep 17 00:00:00 2001
From: Jan Nedbal <janedbal@gmail.com>
Date: Thu, 2 Jul 2026 13:37:04 +0200
Subject: [PATCH] Do not build code unit map when test has no coverage targets

---
 src/CodeCoverage.php             | 8 ++++++--
 tests/tests/CodeCoverageTest.php | 6 ++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/CodeCoverage.php b/src/CodeCoverage.php
index b146899bb..6da9d6051 100644
--- a/src/CodeCoverage.php
+++ b/src/CodeCoverage.php
@@ -259,10 +259,10 @@ public function append(RawCodeCoverageData $rawData, ?string $id = null, bool $a
         $linesToBeUsed    = [];
 
         if ($covers !== false) {
-            $linesToBeCovered = $this->targetMapper()->mapTargets($covers);
+            $linesToBeCovered = $covers->isEmpty() ? [] : $this->targetMapper()->mapTargets($covers);
         }
 
-        if ($linesToBeCovered !== false) {
+        if ($linesToBeCovered !== false && $uses->isNotEmpty()) {
             $linesToBeUsed = $this->targetMapper()->mapTargets($uses);
         }
 
@@ -403,6 +403,10 @@ public function collectsBranchAndPathCoverage(): bool
 
     public function validate(TargetCollection $targets): ValidationResult
     {
+        if ($targets->isEmpty()) {
+            return ValidationResult::success();
+        }
+
         return (new TargetCollectionValidator)->validate($this->targetMapper(), $targets);
     }
 
diff --git a/tests/tests/CodeCoverageTest.php b/tests/tests/CodeCoverageTest.php
index 895be4588..246972b8e 100644
--- a/tests/tests/CodeCoverageTest.php
+++ b/tests/tests/CodeCoverageTest.php
@@ -14,6 +14,7 @@
 use SebastianBergmann\CodeCoverage\Data\RawCodeCoverageData;
 use SebastianBergmann\CodeCoverage\Driver\Driver;
 use SebastianBergmann\CodeCoverage\Driver\Selector;
+use SebastianBergmann\CodeCoverage\Test\Target\TargetCollection;
 use SebastianBergmann\Environment\Runtime;
 
 #[CoversClass(CodeCoverage::class)]
@@ -140,4 +141,9 @@ public function testMerge2(): void
             $coverage->getData()->lineCoverage(),
         );
     }
+
+    public function testEmptyTargetCollectionIsValidWithoutBuildingCodeUnitMap(): void
+    {
+        $this->assertTrue($this->coverage->validate(TargetCollection::fromArray([]))->isSuccess());
+    }
 }