dmypy only formats output in json the first time it's executed

[johnfn]

Bug Report

dmypy only outputs in json the first time it's invoked with --output=json.

To Reproduce

dmypy stop
dmypy run -- --output=json
dmypy run -- --output=json

Expected Behavior

Every invocation returns JSON.

Actual Behavior

Only the first one does.

$ dmypy run -- --output=json
Daemon started
{"file": "myfile.py", "line": 3, "column": 0, "message": "Function is missing a type annotation", "hint": null, "code": "no-untyped-def", "severity": "error"}

$ dmypy run -- --output=json
a_different_file.py:22: error: Missing type parameters for generic type "Query"  [type-arg]

Your Environment

mypy --version
mypy 1.15.0 (compiled: yes)

python --version
Python 3.11.11