Log Format String Companion (VS Code)

Flags a log call whose placeholder count doesn't match its argument count — SLF4J-style {} (Java/Kotlin) and Python %-style logging. No data leaves your editor.

v0.1, pilot. Part of the Gap Hunter Labs VS Code workstream, ported from the IntelliJ-family log-format-string-companion.

What it does

Live in .java/.kt/.py files, on any log.info(...)/ logger.warn(...)/etc. call (receiver must be named log or logger, exactly — not a substring match, so catalog/dialog don't trip it):

• SLF4J-style: log.info("User {} logged in from {}", userId, ipAddress) — counts {} in the message, compares against the trailing arguments.
• Python %-style: logger.info("User %s logged in", user_id) — counts %s/%d/%r/etc. (never a literal %% escape).

The SLF4J trailing-Throwable special case, ported faithfully: SLF4J treats a trailing Throwable argument as the exception to log, not a placeholder argument — log.error("Failed for {}", userId, exception) (1 placeholder, 2 arguments) is correct, never flagged. An excess of exactly 1 argument is only flagged when its own syntax makes it unambiguous that it can't be a Throwable (a string/number/ boolean literal) — an identifier or method call is left alone (false negative preferred over false positive).

Python f-strings are deliberately NOT scanned (same as the original): an f-string's interpolations are inline expressions, not separate arguments, so there's no placeholder-count-vs-argument-count mismatch to detect in this shape.

v0.1 scope, honestly noted: a message literal built by concatenation/interpolation instead of a plain string constant is out of scope — reliably counting placeholders needs a literal the scanner can read directly.

Privacy

See PRIVACY.md — zero network calls, everything runs against files already open in your editor.

Development

npm install
npm run compile   # or: npm run watch
npm test

To build an installable package without publishing:

npx @vscode/vsce package

License

Apache License 2.0 — see LICENSE.