Add new interface for transformers + add force strict types transformer

Author: AydinHassan

src/Patch/ForceStrictTypes.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace PhpSchool\PhpWorkshop\Patch;
+
+use PhpParser\Node\Scalar\LNumber;
+use PhpParser\Node\Stmt\Declare_;
+use PhpParser\Node\Stmt\DeclareDeclare;
+
+class ForceStrictTypes implements Transformer
+{
+    public function transform(array $ast): array
+    {
+        if ($this->isFirstStatementStrictTypesDeclare($ast)) {
+            return $ast;
+        }
+
+        $declare = new \PhpParser\Node\Stmt\Declare_([
+            new DeclareDeclare(
+                new \PhpParser\Node\Identifier('strict_types'),
+                new LNumber(1)
+            )
+        ]);
+
+        return array_merge([$declare], $ast);
+    }
+
+    public function isFirstStatementStrictTypesDeclare(array $statements): bool
+    {
+        return isset($statements[0]) && $statements[0] instanceof Declare_;
+    }
+}

src/Patch/Transformer.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace PhpSchool\PhpWorkshop\Patch;
+
+interface Transformer
+{
+    public function transform(array $ast): array;
+}

test/Patch/ForceStrictTypesTest.php

@@ -0,0 +1,39 @@
+<?php
+
+namespace PhpSchool\PhpWorkshopTest\Patch;
+
+use PhpParser\ParserFactory;
+use PhpParser\PrettyPrinter\Standard;
+use PhpSchool\PhpWorkshop\Patch\ForceStrictTypes;
+use PHPUnit\Framework\TestCase;
+
+class ForceStrictTypesTest extends TestCase
+{
+    public function testStrictTypesDeclareIsAppended(): void
+    {
+        $parser = (new ParserFactory())->create(ParserFactory::PREFER_PHP7);
+        $ast = $parser->parse("<?php echo 'Hello World';");
+
+        $transformer = new ForceStrictTypes();
+        $ast = $transformer->transform($ast);
+
+        self::assertSame(
+            "declare (strict_types=1);\necho 'Hello World';",
+            (new Standard())->prettyPrint($ast)
+        );
+    }
+
+    public function testStrictTypesDeclareIsNotAppendedIfItAlreadyExists(): void
+    {
+        $parser = (new ParserFactory())->create(ParserFactory::PREFER_PHP7);
+        $ast = $parser->parse("<?php declare (strict_types=1);\necho 'Hello World';");
+        $transformer = new ForceStrictTypes();
+
+        $ast = $transformer->transform($ast);
+
+        self::assertSame(
+            "declare (strict_types=1);\necho 'Hello World';",
+            (new Standard())->prettyPrint($ast)
+        );
+    }
+}