Persistent SyntaxError: JSON.parse Fails Regardless of HTML or JSON Respons

[misterbredjenn]

I am encountering a SyntaxError in the HTMX library when making requests that return either JSON or HTML responses. Despite the requests being successful (i.e., the server responds with a status code of 200 and the expected data), the following error appears in the console:

SyntaxError: Expected property name or '}' in JSON at position 1 (line 1 column 2)
at JSON.parse ()
at S (htmx.min.js:1:5757)
at bn (htmx.min.js:1:36513)
...

Steps to Reproduce
Set up a view in Django that handles POST requests and returns either a JSON response or an HTML response.
Send a request using HTMX (e.g., via hx-post or hx-get, i try with hx-boost to and still getting the error).
Observe the console for the SyntaxError, even though the request completes successfully.
Expected Behavior
The HTMX request should process the response without throwing a SyntaxError.

Actual Behavior
The error persists in the console regardless of whether the response is HTML or JSON, causing confusion since the request appears to work correctly.

Additional Information
HTMX Version: 2.0.3
Server Response:
For JSON: {"message": "Test success!"}
Any insights into why this error occurs despite successful requests would be greatly appreciated!

[MichaelWest22]

From the exception line/col number it shows that it was trying to parse the json of a HX-Trigger resonse header https://htmx.org/headers/hx-trigger/ that must be returning from the server response with invalid data that is not in the correct JSON format which is expected to fail with a syntax error in this situation.

The htmx code detects if the hx-trigger header in the response starts with the character { and if it does it will try and process it as JSON. It is likely that you have the hx-trigger header set to a dynamic placeholder variable wrapped in {} that is getting sent in error.

When trying to debug problems in htmx it is best to switch to using the un-minified version of htmx.js like in https://htmx.org/docs/#via-a-cdn-e-g-unpkg-com or host the full htmx.js locally as it makes reading the error responses and understanding what function broke trivial.

[misterbredjenn]

my fault, the error was due to invalid JSON syntax in the hx-headers attribute in my HTML template. HTMX expects hx-headers to be a valid JSON object, and I had mistakenly used single quotes instead of double quotes.

To fix it, I updated the hx-headers attribute with proper JSON syntax by replacing single quotes with double quotes

Thanks for the help and insights!