No Debug Call

Use of functions that are intended primarily for debugging should be avoided.

Rationale

Debug-oriented APIs are invaluable while developing, but they are easy to leave in paths that later run in CI, libraries, or production. They often write to the console, bypass structured logging, or enable heavy tracing—hurting performance, polluting output, and making behavior harder to control than a proper logger configuration.

Note: the specific functions to flag are configured via the debug_functions option.

Rationale for default debug_functions

Defaults favor “obvious debug helpers” and tracing hooks; adjust the list if your project uses some of these intentionally in non-debug code.

• ct:pal/* and ct:print/* — Common Test helpers for interactive runs; they should not appear outside test code.
• erlang:display/1 — Prints to standard output for ad hoc inspection; prefer logging or explicit test assertions.
• io:format/1,2 and io:put_chars/1,2 — Often used as quick prints; production diagnostics should go through logger (or your application’s logging facade) for levels, formatters, and sinks.
• dbg, dyntrace, and instrument (any function) — Low-level tracing and debugging facilities; leaving calls in normal code paths can enable expensive work or surprise operators.

{erlang, display, 1} was added in 1.5.0.

{io, put_chars, 1}, {io, put_chars, 2} was added in 4.0.0.

{dbg, '_'}, {dyntrace, '_'}, {instrument, '_'} was added in 4.1.0.

Options

• debug_functions :: [{module(), function(), arity()} | {module(), function()}]

  • default: [{ct, pal}, {ct, print}, {erlang, display, 1}, {io, format, 1}, {io, format, 2}, {io, put_chars, 1}, {io, put_chars, 2}, {dbg, '_'}, {dyntrace, '_'}, {instrument, '_'}]

Example configuration

{elvis_style, no_debug_call, #{
    debug_functions => [
        {ct, pal},
        {ct, print},
        {erlang, display, 1},
        {io, format, 1},
        {io, format, 2},
        {io, put_chars, 1},
        {io, put_chars, 2},
        {dbg, '_'},
        {dyntrace, '_'},
        {instrument, '_'}
    ]
}}