feature: add support for Coccinelle-like semantic patches mixing matching (TemplateMatcher) and transformation (Template) together

[monperrus]

Imagine that you want to match a code location and transform it at the same time, this is sometimes called a "semantic patch" (as opposed to a line-based patch).

In the C world, there is an excellent tool for this, called Coccinelle, see http://coccinelle.lip6.fr/.

In Spoon, it would mean creating an abstraction that would gather a TemplateMatcher and Template in a same object. In other terms, we are really close to have "semantic patches" in Spoon.

@pvojtechovsky since you're extensively working on this part, what do you think?

[pvojtechovsky]

I am not sure if I understood you well. But have a look at
https://github.com/pvojtechovsky/spoon/blob/5919ed784e5fde86e4b9246c0ea24c989f269a45/src/test/java/spoon/test/template/CodeReplaceTest.java testTemplateReplace

There are two patterns, first is matching (founds a code location and takes current parameters) and second generates new code (using own template and current parameters) and then old code is replaced by new code.

[pvojtechovsky]

Have a look at https://github.com/pvojtechovsky/spoon/blob/5919ed784e5fde86e4b9246c0ea24c989f269a45/src/main/java/spoon/pattern/node/RootNode.java too
It is the core interface of Pattern node, which shows that Pattern can always do both matching and generating:

public interface RootNode extends Matchers {
/**
	 * Generates zero, one or more target depending on kind of this {@link RootNode}, expected `result` and input `parameters`
	 * @param generator {@link Generator} which drives generation process
	 * @param result holder for the generated objects
	 * @param parameters a {@link ParameterValueProvider} holding parameters
	 */
	<T> void generateTargets(Generator generator, ResultHolder<T> result, ParameterValueProvider parameters);
/**
	 * @param targets to be matched target nodes and input parameters
	 * @param nextMatchers Chain of matchers which has to be processed after this {@link RootNode}
	 * @return new parameters and container with remaining targets
	 */
	TobeMatched matchTargets(TobeMatched targets, Matchers nextMatchers);

[monperrus]

Patterns (#1686) are almost this. The final step is to given then a Coccinelle look'n'feel.

[monperrus]

Documentation about SmPL: http://coccinelle.lip6.fr/documentation.php

[monperrus]

See also
Automating Program Transformation for Java Using Semantic Patches
https://hal.inria.fr/hal-02023368v1

[monperrus]

FYI new version of @JuliaLawall's paper: Semantic Patches for Java Program Transformation

[monperrus]

FYI, a paper on that topic "Semantic Patches for Adaptation of JavaScript Programs to Evolving Libraries." https://cs.au.dk/~amoeller/papers/jsfix/paper.pdf