clang-format adds spurious binding to JSON file with DisableFormat: true

[Andrew-William-Smith]

With clang-format built from the head of main and the following .clang-format file, which should fully disable formatting for JSON files:

---
Language: Json
DisableFormat: true

The following file:

{
  "key": "value"
}

Is reformatted as follows, with a spurious binding that results in invalid JSON:

x = {
  "key": "value"
}

With DisableFormat: false or no .clang-format file at all, the binding is not added to the file.

---

Research note: This issue is a result of the way that clang-format implements JSON formatting by adding a binding to the top-level object in order to force clang::format to treat the code as plain JavaScript. I have already tracked down the issue and am currently preparing a patch.

[Andrew-William-Smith]

Here's an initial diff that fixes this issue: https://reviews.llvm.org/D115769