Acceleo/Specifications/Parser Improvements

Evolution Specification: Improvements of the Acceleo Parser

Current status is DRAFT

Preamble

This page will be used to discuss the evolution of the Acceleo parser.

The possible status are (roughly inspired by PEP-0001):

• DRAFT: Initial version and revisions based on internal feedback and discussions. DRAFT versions should never be made available outside of Obeo. They have version numbers 0.x.
• PROPOSAL: When the document is considered ready for discussion with the client, it becomes a PROPOSAL. The first such version is numbered 1.0. Feedback from the client are integrated in further versions 1.x which are still PROPOSALs. Changes from one version to the next should be documented inside the document (as the client does not have access to the source repository).
• ACCEPTED: Once agreement has been reached with the client, the document becomes ACCEPTED.This version becomes the authoritative one for guiding the evolution's actual implementation. It should normally be considered freezed. Any change to it should be exceptional and subject to approval by the project manager. Such changes must be clearly documented and justified.
• ARCHIVED: Once the evolution has been implemented _and_ its specification has been integrated into the reference documentation, this document is ARCHIVED. Any further change to the same features should be another Viewpoint Evolution .

Relevant tickets

• Bug 350219 - Introduce a cache to improve performances of the compilation and the tooling

Introduction

Several solutions are considered to improve the performances of the Acceleo Parser:

• introduction of Google Collection based caches
• removal of the CST in the parser
• improved the incremental compilation to minimize the recompilation of Acceleo modules

Detailed Specification

The Acceleo parser contains two separate data structures used during the parsing. This proposition aims at the removal of the CST to only keep the AST. This removal would have for consequence a simplification of the Acceleo parser and of some parts of the Acceleo tooling.

This specification also aims at the improvement of the performances of the Acceleo parser with, for example, the introduction of a Google Collection based cache.

Backward Compatibility and Migration Paths

All the mentioned changes should not in any way affect the backward compatibility for those who have created an Acceleo generator.

Metamodel Changes

The removal of the CST would remove its metamodel and all its use in the parser and the tooling. The metamodel used by Acceleo modules (AST) would be intact.

API Changes

API removal: CST API change: The API provided by the Acceleo parser would evolve to reflect the removal of the CST API addition: The new API using only the AST

User Interface Changes

none

Documentation Changes

none

Tests and Non-regression strategy

Parse and save an Acceleo module with the current parser and with the new parser and compare the differences.