[Filesystem] Add a cross-platform readlink method

tgalopin · tgalopin · commit 22d9cc1cf530 · 2016-01-29T11:26:20.000+01:00
diff --git a/src/Symfony/Component/Filesystem/Filesystem.php b/src/Symfony/Component/Filesystem/Filesystem.php
@@ -316,6 +316,76 @@ public function symlink($originDir, $targetDir, $copyOnWindows = false)
         }
     }
 
+    /**
+     * Return the next direct target of a link.
+     *
+     * Tto recursively follow links until a final target
+     * is reached, use @see Filesystem::realpath($path).
+     *
+     * @param string $path A link path.
+     *
+     * @return string Return the resolved link.
+     *
+     * @throws IOException When the link does not exist or is not readable.
+     */
+    public function readlink($path)
+    {
+        if (!$this->exists($path)) {
+            throw new IOException(sprintf('The link %s does not exist and cannot be read.', $path));
+        }
+
+        if (!is_link($path)) {
+            return $path;
+        }
+
+        // On Windows, transitive links are resolved to the final target by
+        // readlink(). realpath(), however, returns the target link on Windows,
+        // but not on Unix.
+
+        // /link1 -> /link2 -> /file
+
+        // Windows: readlink(/link1) => /file
+        //          realpath(/link1) => /link2
+
+        // Unix:    readlink(/link1) => /link2
+        //          realpath(/link1) => /file
+
+        if ('\\' === DIRECTORY_SEPARATOR) {
+            return realpath($path);
+        }
+
+        return readlink($path);
+    }
+
+    /**
+     * Return the final target of a link by recursively following links.
+     *
+     * To find only the direct next target of a link,
+     * use @see Filesystem::readlink($path).
+     *
+     * @param string $path A link path.
+     *
+     * @return string Return the final target of the link.
+     *
+     * @throws IOException When the link does not exist or is not readable.
+     */
+    public function realpath($path)
+    {
+        if (!$this->exists($path)) {
+            throw new IOException(sprintf('The link %s does not exist and cannot be read.', $path));
+        }
+
+        if (!is_link($path)) {
+            return $path;
+        }
+
+        if ('\\' === DIRECTORY_SEPARATOR) {
+            return readlink($path);
+        }
+
+        return realpath($path);
+    }
+
     /**
      * Given an existing path, convert it to a path relative to a given starting path.
      *
diff --git a/src/Symfony/Component/Filesystem/Tests/FilesystemTest.php b/src/Symfony/Component/Filesystem/Tests/FilesystemTest.php
@@ -767,6 +767,78 @@ public function testSymlinkCreatesTargetDirectoryIfItDoesNotExist()
         $this->assertEquals($file, readlink($link2));
     }
 
+    public function testReadLink()
+    {
+        $this->markAsSkippedIfSymlinkIsMissing();
+
+        $file = $this->workspace.DIRECTORY_SEPARATOR.'file';
+        $link1 = $this->workspace.DIRECTORY_SEPARATOR.'dir'.DIRECTORY_SEPARATOR.'link';
+        $link2 = $this->workspace.DIRECTORY_SEPARATOR.'dir'.DIRECTORY_SEPARATOR.'subdir'.DIRECTORY_SEPARATOR.'link';
+
+        touch($file);
+
+        $this->filesystem->symlink($file, $link1);
+        $this->filesystem->symlink($link1, $link2);
+
+        $this->assertTrue(is_link($link1));
+        $this->assertEquals($file, $this->filesystem->readlink($link1));
+        $this->assertTrue(is_link($link2));
+        $this->assertEquals($link1, $this->filesystem->readlink($link2));
+    }
+
+    public function testReadLinkNotLink()
+    {
+        $file = $this->workspace.DIRECTORY_SEPARATOR.'file';
+
+        touch($file);
+
+        $this->assertEquals($file, $this->filesystem->readlink($file));
+    }
+
+    /**
+     * @expectedException \Symfony\Component\Filesystem\Exception\IOException
+     */
+    public function testReadLinkFails()
+    {
+        $this->filesystem->readlink($this->workspace.DIRECTORY_SEPARATOR.'invalid');
+    }
+
+    public function testRealPath()
+    {
+        $this->markAsSkippedIfSymlinkIsMissing();
+
+        $file = $this->workspace.DIRECTORY_SEPARATOR.'file';
+        $link1 = $this->workspace.DIRECTORY_SEPARATOR.'dir'.DIRECTORY_SEPARATOR.'link';
+        $link2 = $this->workspace.DIRECTORY_SEPARATOR.'dir'.DIRECTORY_SEPARATOR.'subdir'.DIRECTORY_SEPARATOR.'link';
+
+        touch($file);
+
+        $this->filesystem->symlink($file, $link1);
+        $this->filesystem->symlink($link1, $link2);
+
+        $this->assertTrue(is_link($link1));
+        $this->assertEquals($file, $this->filesystem->realpath($link1));
+        $this->assertTrue(is_link($link2));
+        $this->assertEquals($file, $this->filesystem->realpath($link2));
+    }
+
+    public function testRealPathNotLink()
+    {
+        $file = $this->workspace.DIRECTORY_SEPARATOR.'file';
+
+        touch($file);
+
+        $this->assertEquals($file, $this->filesystem->realpath($file));
+    }
+
+    /**
+     * @expectedException \Symfony\Component\Filesystem\Exception\IOException
+     */
+    public function testRealPathFails()
+    {
+        $this->filesystem->realpath($this->workspace.DIRECTORY_SEPARATOR.'invalid');
+    }
+
     /**
      * @dataProvider providePathsForMakePathRelative
      */
