Feature Guide

Feature

Feature Callback Methods

To implement a feature, you can choose to provide below methods.

Method NameDescription
setUp(config)Do the setup
finalize(config)Do the finalization
accept(context)If the feature accepts this kind of AST node
run(context)Run the feature against the AST node
groupBy(context)Get the string to group the AST nodes
runGroup(group)Run the feature against the AST node group

AST Node

Most of the job that a feature does is to handle the AST nodes.

You have two ways to do it.

  • Direct Manipulation

You create AST nodes purely from javascript and set all the attributes, which is suitable for simple cases.

Example:

const newNode = {
    name: {
        identifier: "mod",
        node: "SimpleName",
    },
    expression: {
        identifier: "Math",
        node: "SimpleName",
    },
    node: "MethodInvocation",
    arguments: [
        current.leftOperand,
        current.rightOperand,
    ],
    typeArguments: [],
};
  • Parse From String

You construct the string and parse it to create the AST node, preferably to be used in complex cases.

Example:

const newFuncTypeContent =
    `private class ${funcClassName} extends Func {
        public ${funcClassName}() {
            super(${_.size(parameters)});
        }

        public override Object execN(List args) {
            ${castStatements};
            ${lines.join('\n')};
        }
    }`;
const newFuncType = AST.parseTypeDeclaration(newFuncTypeContent);
AST Processing
You can choose either way to create new AST nodes, but when it comes to impacting the existing AST nodes, you have to use the AST utility library to do this.
AST.removeChild(methodDeclaration, 'modifiers', annotation);
AST.removeChildren(methodDeclaration.body, 'statements');
Batch Processing
If you want to process a group of AST nodes that have some similarities, you can implement groupBy and runGroup, instead of run.
Check src/features/not_null/index.js for details.
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