Panic message on malformed JSON causes Vim to replace file content with panic message

[ssokolow]

I like to use jsonfmt as my equalprg filter for JSON files in Vim so I can reindent a file with a simple ==. However, if the file is malformed (eg. a hand-edited JSON file where I neglected to remove an extra comma after reordering a list), then that'll result in the JSON in my Vim buffer being replaced with jsonfmt's panic message.

As you might guess, this also makes it completely unsuitable for automatic format-on-save.

Would you be willing to consider something like a command-line switch which causes it to echo out the input unchanged and without any error messages if serde_json fails to parse the input?