Inconsistent Handling of Empty JSON Request Body in Hono Validator

[ilshm]

What version of Hono are you using?

4.3.3

What runtime/platform is your app running on?

Bun

What steps can reproduce the bug?

1. Send a request with an empty JSON body to a route utilizing hono/validator middleware.
2. Observe the unexpected 400 Bad Request response due to the middleware's exception handling for empty JSON bodies.

What is the expected behavior?

The hono/validator middleware should gracefully handle empty JSON request bodies, considering them valid without triggering exceptions. This behavior is crucial for scenarios where empty JSON bodies are legitimate or expected.

What do you see instead?

The current behavior negatively affects applications where empty JSON request bodies should be permitted. This inconsistency leads to unexpected errors and hinders the module's usability.

Additional information

This issue is critical for applications relying on hono/validator. A swift resolution or workaround would greatly benefit the developer community.

[monoald]

Hello @ilshm, can you send the code to see how did you setup the middleware, and how are you making the request?

I just reproduce the steps to see the bug, but the request is successful, I have no error.

[ilshm]

Hello @ilshm, can you send the code to see how did you setup the middleware, and how are you making the request?

I just reproduce the steps to see the bug, but the request is successful, I have no error.

Hello again, something like this, as I remember:

const route = app.post(
  '/posts',
  zValidator(
    'json',
    z.object({
      title: z.string().optional(),
    })
  ),
  (c) => {
    const title = c.req.valid("json");
    // ... use your validated data
  }
)

Request was made from cURL and Thunder Client.

Hope this helps!

[monoald]

I thought you were using the hono/validator middleware, but again I have no error.

This is how I made the request with curl:

curl -X POST "http://localhost:8787/posts"  \
     -H "Content-Type: application/json" \
     -d "{}"

[ilshm]

I thought you were using the hono/validator middleware, but again I have no error.

hono/zod-validator relies on hono/validator

This is how I made the request with curl

I made it without any JSON in body, and without any headers, like so:
curl -X POST "http://localhost:8787/posts"

I have no error

I get Invalid HTTP header: Content-Type=undefined

To circumvent this issue, I've adjusted the middleware (hono/validator) as follows:

validator.ts

      case 'json':
        try {
          value = await c.req.json()
        } catch {}
        break

[monoald]

Oh, I didn't know that hono/zod-validator relies on hono/validator

I don't think the behavior should be changed in hono/validator, just send the corresponding Content-Type header and an empty json in the body. those validations are to ensure hono receives the expected values when you set the type in the validation

[Sheharyar566]

I'm also facing this on node-template and using nodejs. However, I think, it'd be a better idea to keep the behavior as is, but update the message it sends back. For example,

in case of empty body, we should send a message like "Expected body, received undefined" or something.. something that makes it a bit clear that the dev should really send body.