[Feature] Direct AST-based format-preserving source-code transformation

[lisachenko]

Current version of framework installs the PHP stream filter php_user_filter defined in the SourceTransformingLoader which creates a Data-Transfer-Object StreamMetaData, triggers the transformation process and returns the transformed code back from filter call:

$metadata = new StreamMetaData($this->stream, $this->data);
self::transformCode($metadata);
....
$bucket = stream_bucket_new($this->stream, $metadata->source);
stream_bucket_append($out, $bucket);

StreamMetaData uses goaop/parser-reflection and underlying nikic/parser-reflection library to parse source code into AST and tokens:

$this->syntaxTree = ReflectionEngine::parseFile($this->uri, $source);
$this->setTokenStreamFromRawTokens(...ReflectionEngine::getParser()->getTokens());

goaop/parser-reflection has implemented the format-preserving AST transformation and pretty-printing in goaop/parser-reflection#137 according to the https://github.com/nikic/PHP-Parser/blob/master/doc/component/Pretty_printing.markdown

ClassLoading and Transformer namespaces and classes inside should be refactored into traditional AST node walkers/transformers instead of token manipulation. And once AST will be transformed into $newStmts, PrettyPrinter will be used together with $oldStmts, $oldTokens to pretty-print transformed version of code back. It is important to ensure that line numbers in original source code and transformed should match, so if change is introduced in line - it should remain in that line. StreamMetadata->source should be removed, as new version will work around AST.

Code and tests should pass phpunit tests and phpstan analysis.

[lisachenko]

Looks like this will not work, as even pretty-printing of AST causes some lines to be removed and not preserved. Intermediate result is here: https://github.com/goaop/framework/tree/wip/copilot-ast-based-transforming-attempt