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eslint-template-visitor
Advanced tools
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Simplify eslint rules by visiting templates
npm install eslint-template-visitor
# or
yarn add eslint-template-visitor
+const eslintTemplateVisitor = require('eslint-template-visitor');
+
+const templates = eslintTemplateVisitor();
+
+const objectVariable = templates.variable();
+const argumentsVariable = templates.spreadVariable();
+
+const substrCallTemplate = templates.template`${objectVariable}.substr(${argumentsVariable})`;
const create = context => {
const sourceCode = context.getSourceCode();
- return {
- CallExpression(node) {
- if (node.callee.type !== 'MemberExpression'
- || node.callee.property.type !== 'Identifier'
- || node.callee.property.name !== 'substr'
- ) {
- return;
- }
-
- const objectNode = node.callee.object;
+ return templates.visitor({
+ [substrCallTemplate](node) {
+ const objectNode = substrCallTemplate.context.getMatch(objectVariable);
+ const argumentNodes = substrCallTemplate.context.getMatch(argumentsVariable);
const problem = {
node,
message: 'Prefer `String#slice()` over `String#substr()`.',
};
- const canFix = node.arguments.length === 0;
+ const canFix = argumentNodes.length === 0;
if (canFix) {
problem.fix = fixer => fixer.replaceText(node, sourceCode.getText(objectNode) + '.slice()');
}
context.report(problem);
},
- };
+ });
};
See examples for more.
eslintTemplateVisitor(options?)
Craete a template visitor.
Example:
const eslintTemplateVisitor = require('eslint-template-visitor');
const templates = eslintTemplateVisitor();
options
Type: object
parserOptions
Options for the template parser. Passed down to @babel/eslint-parser
.
Example:
const templates = eslintTemplateVisitor({
parserOptions: {
ecmaVersion: 2018,
},
});
templates.variable()
Create a variable to be used in a template. Such a variable can match exactly one AST node.
templates.spreadVariable()
Create a spread variable. Spread variable can match an array of AST nodes.
This is useful for matching a number of arguments in a call or a number of statements in a block.
templates.variableDeclarationVariable()
Create a variable declaration variable. Variable declaration variable can match any type of variable declaration node.
This is useful for matching any variable declaration, be it const
, let
or var
.
Use it in place of a variable declaration keyword:
const variableDeclarationVariable = templates.variableDeclarationVariable();
const template = templates.template`() => {
${variableDeclarationVariable} x = y;
}`;
templates.template
tagCreates a template possibly containing variables.
Example:
const objectVariable = templates.variable();
const argumentsVariable = templates.spreadVariable();
const substrCallTemplate = templates.template`${objectVariable}.substr(${argumentsVariable})`;
const create = () => templates.visitor({
[substrCallTemplate](node) {
// `node` here is the matching `.substr` call (i.e. `CallExpression`)
}
});
templates.visitor({ /* visitors */ })
Used to merge template visitors with common ESLint visitors.
Example:
const create = () => templates.visitor({
[substrCallTemplate](node) {
// Template visitor
},
FunctionDeclaration(node) {
// Simple node type visitor
},
'IfStatement > BlockStatement'(node) {
// ESLint selector visitor
},
});
template.context
A template match context. This property is defined only within a visitor call (in other words, only when working on a matching node).
Example:
const create = () => templates.visitor({
[substrCallTemplate](node) {
// `substrCallTemplate.context` can be used here
},
FunctionDeclaration(node) {
// `substrCallTemplate.context` is not defined here, and it does not make sense to use it here,
// since we `substrCallTemplate` did not match an AST node.
},
});
template.context.getMatch(variable)
Used to get a match for a variable.
Example:
const objectVariable = templates.variable();
const argumentsVariable = templates.spreadVariable();
const substrCallTemplate = templates.template`${objectVariable}.substr(${argumentsVariable})`;
const create = () => templates.visitor({
[substrCallTemplate](node) {
const objectNode = substrCallTemplate.context.getMatch(objectVariable);
// For example, let's check if `objectNode` is an `Identifier`: `objectNode.type === 'Identifier'`
const argumentNodes = substrCallTemplate.context.getMatch(argumentsVariable);
// `Array.isArray(argumentNodes) === true`
},
});
template.narrow(selector, targetMatchIndex = 0)
Narrow the template to a part of the AST matching the selector.
Sometimes you can not define a wanted template at the top level due to JS syntax limitations.
For example, you can't have await
or yield
at the top level of a script.
Use a wrapper function in the template and then narrow
it to a wanted AST node:
const template = templates.template`
async () => { await 1; }
`.narrow('BlockStatement > :has(AwaitExpression)');
The template
above is equivalent to this:
const template = templates.template`await 1`;
Except the latter can not be defined directly due to espree
limitations.
FAQs
[![Build Status](https://travis-ci.org/futpib/eslint-template-visitor.svg?branch=master)](https://travis-ci.org/futpib/eslint-template-visitor) [![Coverage Status](https://coveralls.io/repos/github/futpib/eslint-template-visitor/badge.svg?branch=master)](
The npm package eslint-template-visitor receives a total of 234,815 weekly downloads. As such, eslint-template-visitor popularity was classified as popular.
We found that eslint-template-visitor demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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