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valid-expect-in-promise.js
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valid-expect-in-promise.js
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'use strict';
const getDocsUrl = require('./util').getDocsUrl;
const isFunction = require('./util').isFunction;
const reportMsg =
'Promise should be returned to test its fulfillment or rejection';
const isThenOrCatch = node => {
return (
node.property &&
(node.property.name === 'then' || node.property.name === 'catch')
);
};
const isExpectCallPresentInFunction = body => {
if (body.type === 'BlockStatement') {
return body.body.find(line => {
if (line.type === 'ExpressionStatement')
return isExpectCall(line.expression);
if (line.type === 'ReturnStatement') return isExpectCall(line.argument);
});
} else {
return isExpectCall(body);
}
};
const isExpectCall = expression => {
return (
expression &&
expression.type === 'CallExpression' &&
expression.callee.type === 'MemberExpression' &&
expression.callee.object.type === 'CallExpression' &&
expression.callee.object.callee.name === 'expect'
);
};
const reportReturnRequired = (context, node) => {
context.report({
loc: {
end: {
column: node.parent.parent.loc.end.column,
line: node.parent.parent.loc.end.line,
},
start: node.parent.parent.loc.start,
},
message: reportMsg,
node,
});
};
const isPromiseReturnedLater = (node, testFunctionBody) => {
let promiseName;
if (node.parent.parent.type === 'ExpressionStatement') {
promiseName = node.parent.parent.expression.callee.object.name;
} else if (node.parent.parent.type === 'VariableDeclarator') {
promiseName = node.parent.parent.id.name;
}
const lastLineInTestFunc = testFunctionBody[testFunctionBody.length - 1];
return (
lastLineInTestFunc.type === 'ReturnStatement' &&
lastLineInTestFunc.argument.name === promiseName
);
};
const isTestFunc = node => {
return (
node.type === 'CallExpression' &&
(node.callee.name === 'it' || node.callee.name === 'test')
);
};
const getFunctionBody = func => {
if (func.body.type === 'BlockStatement') return func.body.body;
return func.body; //arrow-short-hand-fn
};
const getTestFunction = node => {
let parent = node.parent;
while (parent) {
if (isFunction(parent) && isTestFunc(parent.parent)) {
return parent;
}
parent = parent.parent;
}
};
const isParentThenOrPromiseReturned = (node, testFunctionBody) => {
return (
testFunctionBody.type === 'CallExpression' ||
node.parent.parent.type === 'ReturnStatement' ||
isPromiseReturnedLater(node, testFunctionBody) ||
isThenOrCatch(node.parent.parent)
);
};
const verifyExpectWithReturn = (
promiseCallbacks,
node,
context,
testFunctionBody
) => {
promiseCallbacks.some(promiseCallback => {
if (promiseCallback && isFunction(promiseCallback)) {
if (
isExpectCallPresentInFunction(promiseCallback.body) &&
!isParentThenOrPromiseReturned(node, testFunctionBody)
) {
reportReturnRequired(context, node);
return true;
}
}
});
};
const isAwaitExpression = node => {
return node.parent.parent && node.parent.parent.type === 'AwaitExpression';
};
const isHavingAsyncCallBackParam = testFunction => {
try {
return testFunction.params[0].type === 'Identifier';
} catch (e) {
return false;
}
};
module.exports = {
meta: {
docs: {
url: getDocsUrl('valid-expect-in-promise.md'),
},
},
create(context) {
return {
MemberExpression(node) {
if (
node.type === 'MemberExpression' &&
isThenOrCatch(node) &&
node.parent.type === 'CallExpression' &&
!isAwaitExpression(node)
) {
const testFunction = getTestFunction(node);
if (testFunction && !isHavingAsyncCallBackParam(testFunction)) {
const testFunctionBody = getFunctionBody(testFunction);
const parent = node.parent;
const fulfillmentCallback = parent.arguments[0];
const rejectionCallback = parent.arguments[1];
// then block can have two args, fulfillment & rejection
// then block can have one args, fulfillment
// catch block can have one args, rejection
// ref: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise
verifyExpectWithReturn(
[fulfillmentCallback, rejectionCallback],
node,
context,
testFunctionBody
);
}
}
},
};
},
};