Static analysis cache: rely on content hash

Author: Slamdunk

src/StaticAnalysis/CachingFileAnalyser.php

@@ -16,7 +16,7 @@
  */
 final class CachingFileAnalyser implements FileAnalyser
 {
-    private const CACHE_FORMAT_VERSION = 2;
+    private const CACHE_FORMAT_VERSION = 3;
 
     /**
      * @var FileAnalyser
@@ -41,6 +41,15 @@ public function __construct(string $directory, FileAnalyser $analyser)
         $this->directory = $directory;
     }
 
+    public function hash(string $filename): int
+    {
+        if (!isset($this->cache[$filename])) {
+            $this->process($filename);
+        }
+
+        return $this->cache[$filename]['hash'];
+    }
+
     public function classesIn(string $filename): array
     {
         if (!isset($this->cache[$filename])) {
@@ -100,13 +109,18 @@ public function ignoredLinesFor(string $filename): array
 
     public function process(string $filename): void
     {
-        if ($this->has($filename)) {
-            $this->cache[$filename] = $this->read($filename);
+        if (false !== ($cache = $this->read($filename))) {
+            $hash = ParsingFileAnalyser::computeHashForSource(file_get_contents($filename));
+
+            if ($hash === $cache['hash']) {
+                $this->cache[$filename] = $cache;
 
-            return;
+                return;
+            }
         }
 
         $this->cache[$filename] = [
+            'hash'              => $this->analyser->hash($filename),
             'classesIn'         => $this->analyser->classesIn($filename),
             'traitsIn'          => $this->analyser->traitsIn($filename),
             'functionsIn'       => $this->analyser->functionsIn($filename),
@@ -118,29 +132,20 @@ public function process(string $filename): void
         $this->write($filename, $this->cache[$filename]);
     }
 
-    private function has(string $filename): bool
+    /**
+     * @return mixed
+     */
+    private function read(string $filename)
     {
         $cacheFile = $this->cacheFile($filename);
 
         if (!is_file($cacheFile)) {
             return false;
         }
 
-        if (filemtime($cacheFile) < filemtime($filename)) {
-            return false;
-        }
-
-        return true;
-    }
-
-    /**
-     * @return mixed
-     */
-    private function read(string $filename)
-    {
         return unserialize(
             file_get_contents(
-                $this->cacheFile($filename)
+                $cacheFile
             ),
             ['allowed_classes' => false]
         );

src/StaticAnalysis/FileAnalyser.php

@@ -14,6 +14,8 @@
  */
 interface FileAnalyser
 {
+    public function hash(string $filename): int;
+
     public function classesIn(string $filename): array;
 
     public function traitsIn(string $filename): array;

src/StaticAnalysis/ParsingFileAnalyser.php

@@ -31,6 +31,11 @@
  */
 final class ParsingFileAnalyser implements FileAnalyser
 {
+    /**
+     * @var array
+     */
+    private $hash = [];
+
     /**
      * @var array
      */
@@ -71,12 +76,24 @@ final class ParsingFileAnalyser implements FileAnalyser
      */
     private $ignoreDeprecatedCode;
 
+    public static function computeHashForSource(string $source): int
+    {
+        return crc32($source);
+    }
+
     public function __construct(bool $useAnnotationsForIgnoringCode, bool $ignoreDeprecatedCode)
     {
         $this->useAnnotationsForIgnoringCode = $useAnnotationsForIgnoringCode;
         $this->ignoreDeprecatedCode          = $ignoreDeprecatedCode;
     }
 
+    public function hash(string $filename): int
+    {
+        $this->analyse($filename);
+
+        return $this->hash[$filename];
+    }
+
     public function classesIn(string $filename): array
     {
         $this->analyse($filename);
@@ -177,6 +194,7 @@ private function analyse(string $filename): void
         }
         // @codeCoverageIgnoreEnd
 
+        $this->hash[$filename]            = self::computeHashForSource($source);
         $this->classes[$filename]         = $codeUnitFindingVisitor->classes();
         $this->traits[$filename]          = $codeUnitFindingVisitor->traits();
         $this->functions[$filename]       = $codeUnitFindingVisitor->functions();