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Keep exception stacktrace when an assertion fails
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Fixes chaijs#268
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@blastrock
blastrock committed Jul 20, 2021
1 parent 39bfd34 commit 6a16f20
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Showing 3 changed files with 79 additions and 33 deletions.
85 changes: 52 additions & 33 deletions lib/chai-as-promised.js
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,18 @@ module.exports = (chai, utils) => {
promise.then(() => done(), done);
}

function replaceExceptionStack(f, originalError) {
try {
f();
} catch (e) {
if (originalError) {
const messageLines = (originalError.message.match(/\n/g) || []).length + 1;
e.stack = e.message + "\n" + originalError.stack.split("\n").slice(messageLines).join("\n");
}
throw e;
}
}

// These are for clarity and to bypass Chai refusing to allow `undefined` as actual when used with `assert`.
function assertIfNegated(assertion, message, extra) {
assertion.assert(true, null, message, extra.expected, extra.actual);
Expand Down Expand Up @@ -98,9 +110,11 @@ module.exports = (chai, utils) => {
return value;
},
reason => {
assertIfNotNegated(this,
"expected promise to be fulfilled but it was rejected with #{act}",
{ actual: getReasonName(reason) });
replaceExceptionStack(() =>
assertIfNotNegated(this,
"expected promise to be fulfilled but it was rejected with #{act}",
{ actual: getReasonName(reason) }),
reason);
return reason;
}
);
Expand All @@ -118,9 +132,12 @@ module.exports = (chai, utils) => {
return value;
},
reason => {
assertIfNegated(this,
"expected promise not to be rejected but it was rejected with #{act}",
{ actual: getReasonName(reason) });
replaceExceptionStack(() =>
assertIfNegated(this,
"expected promise not to be rejected but it was rejected with #{act}",
{ actual: getReasonName(reason) },
reason),
reason);

// Return the reason, transforming this into a fulfillment, to allow further assertions, e.g.
// `promise.should.be.rejected.and.eventually.equal("reason")`.
Expand Down Expand Up @@ -192,34 +209,36 @@ module.exports = (chai, utils) => {

const reasonName = getReasonName(reason);

if (negate && everyArgIsDefined) {
if (errorLikeCompatible && errMsgMatcherCompatible) {
this.assert(true,
null,
"expected promise not to be rejected with #{exp} but it was rejected " +
"with #{act}",
errorLikeName,
reasonName);
}
} else {
if (errorLike) {
this.assert(errorLikeCompatible,
"expected promise to be rejected with #{exp} but it was rejected with #{act}",
"expected promise not to be rejected with #{exp} but it was rejected " +
"with #{act}",
errorLikeName,
reasonName);
replaceExceptionStack(() => {
if (negate && everyArgIsDefined) {
if (errorLikeCompatible && errMsgMatcherCompatible) {
this.assert(true,
null,
"expected promise not to be rejected with #{exp} but it was rejected " +
"with #{act}",
errorLikeName,
reasonName);
}
} else {
if (errorLike) {
this.assert(errorLikeCompatible,
"expected promise to be rejected with #{exp} but it was rejected with #{act}",
"expected promise not to be rejected with #{exp} but it was rejected " +
"with #{act}",
errorLikeName,
reasonName);
}

if (errMsgMatcher) {
this.assert(errMsgMatcherCompatible,
`expected promise to be rejected with an error ${matcherRelation} #{exp} ` +
`but got #{act}`,
`expected promise not to be rejected with an error ${matcherRelation} #{exp}`,
errMsgMatcher,
checkError.getMessage(reason));
}
}

if (errMsgMatcher) {
this.assert(errMsgMatcherCompatible,
`expected promise to be rejected with an error ${matcherRelation} #{exp} but got ` +
`#{act}`,
`expected promise not to be rejected with an error ${matcherRelation} #{exp}`,
errMsgMatcher,
checkError.getMessage(reason));
}
}
}, reason);

return reason;
}
Expand Down
21 changes: 21 additions & 0 deletions test/should-promise-specific.js
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Original file line number Diff line number Diff line change
Expand Up @@ -156,6 +156,13 @@ describe("Promise-specific extensions:", () => {
});
});

describe(".fulfilled should keep the exception stack", () => {
shouldFail({
op: () => promise.should.be.fulfilled,
stack: "should-promise-specific.js"
});
});

describe(".not.fulfilled", () => {
shouldPass(() => promise.should.not.be.fulfilled);
});
Expand Down Expand Up @@ -194,13 +201,27 @@ describe("Promise-specific extensions:", () => {
shouldPass(() => promise.should.be.rejectedWith(error));
});

describe(".rejectedWith(differentError) should keep the exception stack if the assertion fails", () => {
shouldFail({
op: () => promise.should.be.rejectedWith(new Error()),
stack: "should-promise-specific.js"
});
});

describe(".not.rejectedWith(theError)", () => {
shouldFail({
op: () => promise.should.not.be.rejectedWith(error),
message: "not to be rejected with 'Error: boo'"
});
});

describe(".not.rejectedWith(theError) should keep the exception stack if the assertion fails", () => {
shouldFail({
op: () => promise.should.not.be.rejectedWith(error),
stack: "should-promise-specific.js"
});
});

describe(".rejectedWith(theError) should allow chaining", () => {
shouldPass(() => promise.should.be.rejectedWith(error).and.eventually.have.property("myProp"));
});
Expand Down
6 changes: 6 additions & 0 deletions test/support/common.js
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@ exports.shouldFail = options => {
const promiseProducer = options.op;
const desiredMessageSubstring = options.message;
const nonDesiredMessageSubstring = options.notMessage;
const desiredStackSubstring = options.stack;

it("should return a promise rejected with an assertion error", done => {
promiseProducer().then(
Expand All @@ -34,6 +35,11 @@ exports.shouldFail = options => {
throw new Error(`Expected promise to be rejected with an AssertionError not containing ` +
`"${nonDesiredMessageSubstring}" but it was rejected with ${reason}`);
}

if (desiredStackSubstring && !reason.stack.includes(desiredStackSubstring)) {
throw new Error(`Expected promise to be rejected with an AssertionError with a stack containing ` +
`"${desiredStackSubstring}" but it was rejected with ${reason}: ${reason.stack}`);
}
}
).then(done, done);
});
Expand Down

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