Deprewriter: On the fly rewriting method deprecations.

Abstract

Deprecations are a common way to indicate that a given feature or API will not be available in subsequent versions of a library or framework. While raising deprecation warnings lets developers of libraries evolve their APIs, the developers of client applications often have to manually rewrite their applications to adapt to the deprecation (removal, new APIs. . . ). Some may use static analysis tools to support the rewriting. However, dynamically-typed languages or the use of reflective features often produce incorrect rewrite candidates. This is a costly activity that can lead to bug introductions.In this article, we present a method deprecation approach and a tool called DEPREWRITER that can automatically rewrite the callers of deprecated methods during program execution. Clients of a deprecated API execute their program and associated tests, and DEPREWRITER dynamically rewrites the source code of methods that called a deprecated API to use the new API.The implementation of DEPREWRITER is based on dynamic program transformation: when a deprecated method is executed, a program transformation engine rewrites and recompiles the caller's code before continuing the execution.The approach presented in this article has been developed by the Pharo consortium. Since 2016, DEPREWRITER is used in production in multiple distributions of the Pharo programming language: Pharo 6, 7, 8, and 9 alpha. This article presents and validates this approach.The validation is done in two steps: first with an analysis of deprecations available in Pharo 8 and second with an open survey of software developers about DEPREWRITER. We studied 367 Pharo 8 deprecations, among which we analyzed the 218 rewriting deprecations that use transformation rules. We identified the validity conditions and reported defects to the community. We also proposed 33 transformation rules to be added to the non-rewriting deprecations. Both contributions were accepted into Pharo 9 alpha. We classified the rules and identified possible points of improvement. In addition, we performed a user survey and collected information from 46 software developers: some of them used existing DEPREWRITER' rules and executed them on their code, others used DEPREWRITER to create rewriting deprecations, and finally, some were not aware of DEPREWRITER. 28 of 46 developers (60%) reported that the rewriting deprecations helped them, while 10 stated the inverse and 8 were uncertain.After discussing the current implementation, we sketch possible implementations for other languages than Pharo, showing that the approach is general enough to be applied to other languages.

DepMiner: Automatic Recommendation of Transformation Rules for Method Deprecation

“…Pharo allows developers to enrich deprecations with code transformation rules [13]. If a client system invokes the deprecated method, its source code is automatically fixed during execution to call the replacement: ↑ s e l f needsFullDefinition Lines 2-5 of the code above demonstrate the syntax of transforming deprecations in Pharo: method isSpecial (name in the first line) is deprecated with a message for the user 'Renamed to #needsFullDefinition' and a transformation rule that replaces method calls to isSpectial with calls to needsFullDefinition.…”

“…To support this practice, Java provides the @Deprecated annotation as well as the @deprecated Javadoc tag that can mark a method or class as deprecated while the @link or @see tags can reference the correct replacement in the source code [18]. Pharo 3 has a powerful deprecation engine called Deprewriter [13]. It allows library developers to add transformation rules to their method deprecations specifying the replacements.…”

How Libraries Evolve: A Survey of Two Industrial Companies and an Open-Source Community

“…Others are hard and may require a week or more. The answers to the second question about the time to update could have been influenced by Deprewriter [12] the automatic deprecation update mechanism that is used by the Pharo community. It allows library developers to annotate method deprecations with transformation rules that will be used to automatically rewrite the call-sites in the client code.…”

“…For example, when we asked how much time it takes for clients to update, the answer could depend on how much of the API was used by a particular client. • The transforming deprecation mechanism of Pharo [12] may have affected how Pharo developers answered this survey. • Inside the three mentioned communities, the surveys were public and participation was optional.…”

“…Some of those approaches are designed for client developers: they allow them to infer the modifications that need to be applied to their systems either by calculating the textual and structural similarity between the source code of the two versions of the library [5], [6] or by mining frequent method call replacements either in library itself [7], [8] or in other client systems that were already updated [9], [10]. Other approaches help library developers support their clients by annotating changed functions with transformation rules [11], [12] or recording the refactorings that were performed on the library to later "replay" them on client systems [13].…”