Fix #4440, #3549 - Request ignores false, 0 and '' as body values

[visortelle]

Axios is frequently used to make requests to REST APIs that are under client's control.

There are APIs that expect boolean values like false, or number values 0 as both are valid JSON values.

I see no reason why it shouldn't work. If there are, please point me to it.

If the authors will approve this PR, I can make the same changes to 0.x and 1.x branches.

Thank you.

---

Related issues:

• Axios 0.25.0 put request ignores 0 and false as a request payload #4440
• Axios 0.21.1 post request ignores false as a request payload #3549

[visortelle]

CI failed with the error unrelated to PR.

Run actions/setup-node@v2
Found in cache @ /opt/hostedtoolcache/node/14.19.3/x64
/opt/hostedtoolcache/node/14.1[9](https://github.com/axios/axios/runs/6856026000?check_suite_focus=true#step:3:10).3/x64/bin/npm config get cache
/home/runner/.npm
Error: getCacheEntry failed: Cache service responded with 503

Maybe rerun can help?

[visortelle]

Ping @jasonsaayman

[jasonsaayman]

Cool passes CI merging

[DigitalBrainJS]

Hmm. This PR does not seem to fix anything - Axios will send valid JSON values with a valid content-type header (application/json) rather than the default application/x-www-form-urlencoded. All value conversions are done in the default request resolver/transformer to match between http and xhr adapters.
Even if Axios didn't support this, this behavior shouldn't be hard-coded inside the adapter, especially without considering the content-type header.
After conversions, the xhr adapter expected to get a payload of one of these types, supported by XMLHttpRequest:

void send();
void send(ArrayBuffer data);
void send(ArrayBufferView data);
void send(Blob data);
void send(Document data);
void send(DOMString? data);
void send(FormData data);

Calls: send(), send(null) and send('') are equal, so simple if(!requestData) was a valid condition.

In addition, the PR does not handle these values in the right way:

• '' (empty string) will be sent as an empty response, as it was before. The JSON string primitive requires quotes ("") for an [empty] string, but not every empty string needs to be encoded as a JSON string only if content-type is set to application/json;
• null will be handled as an empty response too (as it was)

@jasonsaayman maybe this needs to be reviewed again?

[jasonsaayman]

Yeah, I am going to rever this as I should have looked into it a bit more. Thanks for the catch.