[Filesystem] Add the readFile() method

Author: derrabus

CHANGELOG.md

@@ -1,6 +1,11 @@
 CHANGELOG
 =========
 
+7.1
+---
+
+ * Add the `Filesystem::readFile()` method
+
 7.0
 ---
 

Filesystem.php

@@ -694,6 +694,25 @@ public function appendToFile(string $filename, $content, bool $lock = false): vo
         }
     }
 
+    /**
+     * Returns the content of a file as a string.
+     *
+     * @throws IOException If the file cannot be read
+     */
+    public function readFile(string $filename): string
+    {
+        if (is_dir($filename)) {
+            throw new IOException(sprintf('Failed to read file "%s": File is a directory.', $filename));
+        }
+
+        $content = self::box('file_get_contents', $filename);
+        if (false === $content) {
+            throw new IOException(sprintf('Failed to read file "%s": ', $filename).self::$lastError, 0, null, $filename);
+        }
+
+        return $content;
+    }
+
     private function toIterable(string|iterable $files): iterable
     {
         return is_iterable($files) ? $files : [$files];

Tests/FilesystemTest.php

@@ -1802,6 +1802,43 @@ public function testDumpKeepsExistingPermissionsWhenOverwritingAnExistingFile()
         $this->assertFilePermissions(745, $filename);
     }
 
+    public function testReadFile()
+    {
+        $licenseFile = \dirname(__DIR__).'/LICENSE';
+
+        $this->assertStringEqualsFile($licenseFile, $this->filesystem->readFile($licenseFile));
+    }
+
+    public function testReadNonExistentFile()
+    {
+        $this->expectException(IOException::class);
+        $this->expectExceptionMessageMatches('#^Failed to read file ".+/Tests/invalid"\\: file_get_contents\\(.+/Tests/invalid\\)\\: Failed to open stream\\: No such file or directory$#');
+
+        $this->filesystem->readFile(__DIR__.'/invalid');
+    }
+
+    public function testReadDirectory()
+    {
+        $this->expectException(IOException::class);
+        $this->expectExceptionMessageMatches('#^Failed to read file ".+/Tests"\\: File is a directory\\.$#');
+
+        $this->filesystem->readFile(__DIR__);
+    }
+
+    public function testReadUnreadableFile()
+    {
+        $this->markAsSkippedIfChmodIsMissing();
+
+        $filename = $this->workspace.'/unreadable.txt';
+        file_put_contents($filename, 'Hello World');
+        chmod($filename, 0o000);
+
+        $this->expectException(IOException::class);
+        $this->expectExceptionMessageMatches('#^Failed to read file ".+/unreadable.txt"\\: file_get_contents\\(.+/unreadable.txt\\)\\: Failed to open stream\\: Permission denied$#');
+
+        $this->filesystem->readFile($filename);
+    }
+
     public function testCopyShouldKeepExecutionPermission()
     {
         $this->markAsSkippedIfChmodIsMissing();