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Breaking: RuleTester Improvements (refs eslint/rfcs#25) (#12955)
* Breaking: RuleTester Improvements (refs eslint/rfcs#25)

* Use Object.defineProperties

* Rename comment to token in error messages
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mdjermanovic committed Mar 28, 2020
1 parent e0f1b6c commit 78c8cda
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Showing 5 changed files with 287 additions and 48 deletions.
2 changes: 1 addition & 1 deletion docs/developer-guide/nodejs-api.md
Expand Up @@ -886,7 +886,7 @@ In addition to the properties above, invalid test cases can also have the follow
* `suggestions` (array): An array of objects with suggestion details to check. See [Testing Suggestions](#testing-suggestions) for details

If a string is provided as an error instead of an object, the string is used to assert the `message` of the error.
* `output` (string, optional): Asserts the output that will be produced when using this rule for a single pass of autofixing (e.g. with the `--fix` command line flag). If this is `null`, asserts that none of the reported problems suggest autofixes.
* `output` (string, required if the rule fixes code): Asserts the output that will be produced when using this rule for a single pass of autofixing (e.g. with the `--fix` command line flag). If this is `null`, asserts that none of the reported problems suggest autofixes.

Any additional properties of a test case will be passed directly to the linter as config options. For example, a test case can have a `parserOptions` property to configure parser behavior:

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87 changes: 80 additions & 7 deletions lib/rule-tester/rule-tester.js
Expand Up @@ -45,16 +45,20 @@ const
path = require("path"),
util = require("util"),
lodash = require("lodash"),
Traverser = require("../../lib/shared/traverser"),
{ getRuleOptionsSchema, validate } = require("../shared/config-validator"),
{ Linter, SourceCodeFixer, interpolate } = require("../linter");

const ajv = require("../shared/ajv")({ strictDefaults: true });

const espreePath = require.resolve("espree");

//------------------------------------------------------------------------------
// Typedefs
//------------------------------------------------------------------------------

/** @typedef {import("../shared/types").Parser} Parser */

/**
* A test case that is expected to pass lint.
* @typedef {Object} ValidTestCase
Expand Down Expand Up @@ -206,6 +210,70 @@ function sanitize(text) {
);
}

/**
* Define `start`/`end` properties as throwing error.
* @param {string} objName Object name used for error messages.
* @param {ASTNode} node The node to define.
* @returns {void}
*/
function defineStartEndAsError(objName, node) {
Object.defineProperties(node, {
start: {
get() {
throw new Error(`Use ${objName}.range[0] instead of ${objName}.start`);
},
configurable: true,
enumerable: false
},
end: {
get() {
throw new Error(`Use ${objName}.range[1] instead of ${objName}.end`);
},
configurable: true,
enumerable: false
}
});
}

/**
* Define `start`/`end` properties of all nodes of the given AST as throwing error.
* @param {ASTNode} ast The root node to errorize `start`/`end` properties.
* @param {Object} [visitorKeys] Visitor keys to be used for traversing the given ast.
* @returns {void}
*/
function defineStartEndAsErrorInTree(ast, visitorKeys) {
Traverser.traverse(ast, { visitorKeys, enter: defineStartEndAsError.bind(null, "node") });
ast.tokens.forEach(defineStartEndAsError.bind(null, "token"));
ast.comments.forEach(defineStartEndAsError.bind(null, "token"));
}

/**
* Wraps the given parser in order to intercept and modify return values from the `parse` and `parseForESLint` methods, for test purposes.
* In particular, to modify ast nodes, tokens and comments to throw on access to their `start` and `end` properties.
* @param {Parser} parser Parser object.
* @returns {Parser} Wrapped parser object.
*/
function wrapParser(parser) {
if (typeof parser.parseForESLint === "function") {
return {
parseForESLint(...args) {
const ret = parser.parseForESLint(...args);

defineStartEndAsErrorInTree(ret.ast, ret.visitorKeys);
return ret;
}
};
}
return {
parse(...args) {
const ast = parser.parse(...args);

defineStartEndAsErrorInTree(ast);
return ast;
}
};
}

//------------------------------------------------------------------------------
// Public Interface
//------------------------------------------------------------------------------
Expand Down Expand Up @@ -450,9 +518,12 @@ class RuleTester {

if (typeof config.parser === "string") {
assert(path.isAbsolute(config.parser), "Parsers provided as strings to RuleTester must be absolute paths");
linter.defineParser(config.parser, require(config.parser));
} else {
config.parser = espreePath;
}

linter.defineParser(config.parser, wrapParser(require(config.parser)));

if (schema) {
ajv.validateSchema(schema);

Expand Down Expand Up @@ -483,13 +554,9 @@ class RuleTester {

// Verify the code.
const messages = linter.verify(code, config, filename);
const fatalErrorMessage = messages.find(m => m.fatal);

// Ignore syntax errors for backward compatibility if `errors` is a number.
if (typeof item.errors !== "number") {
const errorMessage = messages.find(m => m.fatal);

assert(!errorMessage, `A fatal parsing error occurred: ${errorMessage && errorMessage.message}`);
}
assert(!fatalErrorMessage, `A fatal parsing error occurred: ${fatalErrorMessage && fatalErrorMessage.message}`);

// Verify if autofix makes a syntax error or not.
if (messages.some(m => m.fix)) {
Expand Down Expand Up @@ -772,6 +839,12 @@ class RuleTester {
} else {
assert.strictEqual(result.output, item.output, "Output is incorrect.");
}
} else {
assert.strictEqual(
result.output,
item.code,
"The rule fixed the code. Please add 'output' property."
);
}

assertASTDidntChange(result.beforeAST, result.afterAST);
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