glinter

A linter for the Gleam programming language. It parses Gleam source files into ASTs using glance and checks them against a configurable set of rules. Many rules are based on the official Gleam conventions.

Installation

gleam add --dev glinter

Usage

# Lint the src/ directory (default)
gleam run -m glinter

# Lint specific files or directories
gleam run -m glinter src/myapp/ test/

# JSON output
gleam run -m glinter --format json

# Show stats (files, lines, timing)
gleam run -m glinter --stats

# Lint a different project (resolves gleam.toml and paths relative to project dir)
gleam run -m glinter --project /path/to/my/project

The exit code is 1 if any issues are found, 0 otherwise.

Multi-Package Projects

For monorepos with multiple Gleam packages, add glinter as a dev dependency to one package (e.g. server) and lint each package separately using --project:

# From any directory, lint each package
gleam run -m glinter --project server
gleam run -m glinter --project client
gleam run -m glinter --project shared

Each package uses its own gleam.toml for configuration. You can wrap this in a script to lint all packages at once:

#!/bin/sh
# bin/lint
set -e
for pkg in server client shared; do
  echo "Linting $pkg..."
  gleam run -m glinter --project "$pkg"
done

Rules

Code Quality

Error Handling

Type Annotations

Style

Complexity

Labels

Imports

Cross-Module

FFI

Configuration

Configuration lives in your project's gleam.toml under the [tools.glinter] key:

[tools.glinter]
stats = true  # show file count, line count, and timing after each run
include = ["src/", "test/"]  # directories to lint (default: ["src/"])
exclude = ["src/server/sql.gleam"]  # skip generated files entirely

[tools.glinter.rules]
avoid_panic = "error"
avoid_todo = "error"
echo = "warning"
assert_ok_pattern = "warning"
discarded_result = "warning"
short_variable_name = "warning"
unnecessary_variable = "warning"
redundant_case = "warning"
unwrap_used = "warning"
deep_nesting = "warning"
function_complexity = "off"  # off by default
module_complexity = "off"  # off by default
prefer_guard_clause = "warning"
missing_labels = "warning"
label_possible = "warning"
unused_exports = "warning"
missing_type_annotation = "warning"
todo_without_message = "warning"
unqualified_import = "warning"
panic_without_message = "warning"
string_inspect = "warning"
duplicate_import = "warning"
unnecessary_string_concatenation = "warning"
trailing_underscore = "warning"
error_context_lost = "warning"
stringly_typed_error = "warning"
thrown_away_error = "warning"
ffi_usage = "off"  # off by default

Each rule can be set to "error", "warning", or "off".

Excluding Files

Skip files entirely (useful for generated code). Supports globs:

[tools.glinter]
exclude = ["src/server/sql.gleam", "src/generated/**/*.gleam"]

Ignoring Rules Per File

Suppress specific rules for files where they don't make sense. Also supports globs:

[tools.glinter.ignore]
"src/my_complex_module.gleam" = ["deep_nesting", "function_complexity"]
"test/**/*.gleam" = ["assert_ok_pattern", "short_variable_name", "missing_type_annotation", "label_possible", "missing_labels", "unqualified_import"]

Output Formats

Text (default)

src/app.gleam:12: [error] avoid_panic: Use of 'panic' is discouraged
src/app.gleam:25: [warning] echo: Use of 'echo' is discouraged

JSON

gleam run -m glinter --format json
{
  "results": [
    {
      "rule": "avoid_panic",
      "severity": "error",
      "file": "src/app.gleam",
      "line": 12,
      "message": "Use of 'panic' is discouraged"
    }
  ],
  "summary": {
    "total": 1,
    "errors": 1,
    "warnings": 0
  }
}

When --stats is enabled, a stats object is included:

{
  "stats": {
    "files": 23,
    "lines": 2544,
    "elapsed_ms": 45
  }
}

Running Tests

gleam test

License

MIT