Linter, Formatter and Type Checker Detection — Rules Reference

Rules verified: 2026-10-05 (panopticas 0.0.20) Inventory below generated from: LINTER_RULES in src/panopticas/constants.py

Panopticas detects the configuration and exclusion files of code-quality tooling and tags each with the languages the tool targets, its role, the tool name, and whether the file configures or excludes.

.eslintrc.json   -> ['JavaScript', 'TypeScript', 'linter', 'ESLint', 'config']
.eslintignore    -> ['JavaScript', 'TypeScript', 'linter', 'ESLint', 'ignore']
.rubocop.yml     -> ['Ruby', 'linter', 'formatter', 'RuboCop', 'config']
mypy.ini         -> ['Python', 'typechecker', 'mypy', 'config']
.editorconfig    -> ['formatter', 'EditorConfig', 'config']

This document is the reference and evidence base: what is detected, the source that confirms each convention, and — equally important — what was rejected and why.

How matching works

LINTER_RULES maps a tool to its languages, its roles, and the files that identify it. A single expansion step writes those entries into the same METADATA_RULES tables every other rule uses, so the tags are produced by one code path and the shape cannot drift between tools.

Key	Expands into	Matched against
config	exact_filename_rules	the lowercased basename
ignore	exact_filename_rules	the lowercased basename
path_contains	path_contains_rules	a substring of the path
extensions	extension_rules	the file extension

Tags are languages + roles + [tool] + ["config" or "ignore"]. The three roles are linter, formatter and typechecker; a tool may hold more than one, and several do — Ruff, Biome, RuboCop, Standard and SQLFluff all lint and format.

Unlike AI artifact detection, these rules add tags rather than resolving to a single winner, so eslint.config.js is both JavaScript and an ESLint config.

Detection is path-based only

No rule opens a file. This is the same constraint AI detection works under, and it is what makes the per-language shared config files undetectable:

File	Really can hold	Why it is not tagged
pyproject.toml	Ruff, Black, mypy, isort, yapf, Pylint, Pyright	which tool is inside is not knowable from the path
setup.cfg	Flake8, isort, yapf, mypy	same
tox.ini	Flake8, Pylint	same
package.json	Prettier, ESLint, Stylelint, StandardJS	same

Tagging any of these as a linter config would mislabel every repository that has one, which is most of them. They keep their existing build and dependency tags only.

The rejected list

Each of these was investigated against the tool’s current documentation and deliberately not added. Re-adding one would mislabel repositories.

Candidate	Why rejected
revive (revive.toml)	Auto-discovers only $HOME/revive.toml. A user-level path, not a repository artifact — the same trap AI detection warns about. A project-level config exists but must be passed with -config, under any name.
SpotBugs (spotbugs-exclude.xml)	Filter files are arbitrarily named and passed with -exclude/-include. The documentation’s myExcludeFilter.xml is illustrative, not a convention.
PMD (ruleset.xml)	Ruleset files are arbitrarily named and passed explicitly. No discovered filename.
CodeNarc (codenarc.xml)	Rulesets are arbitrary .xml or .groovy files. Detected indirectly through npm-groovy-lint, which does have a fixed config name.
Black	Configured only in pyproject.toml. No dedicated file exists to match.
StandardJS	Configured only in package.json.
Spotless	Configured only in build.gradle / pom.xml.
gofmt, gofumpt, go vet	No configuration file at all.
pycodestyle	Project-level config lives in setup.cfg or tox.ini; the dedicated file is the user-level ~/.config/pycodestyle.
Sonar, Bandit, Brakeman, GitLeaks	Security scanners, out of scope. GitLeaks is already detected separately via .gitleaksignore.

How dprint was settled

dprint was initially left out because its documentation never enumerates the filenames it discovers. The answer is in the source — POSSIBLE_CONFIG_FILE_NAMES in resolve_main_config_path.rs — which lists exactly four names, searched in order while walking up ancestor directories, with no config/ subdirectory. The setup page corroborates the two hidden variants.

Worth noting against the user-level trap that disqualified revive: dprint also reads a global config at ~/.config/dprint/dprint.jsonc, reusing the dprint.jsonc name. That does not disqualify it. revive’s only auto-discovered config is user-level, so a repository rule would be fiction; dprint’s four names are genuinely project-level, and its global config merely shares a name in a different directory.

Two judgement calls worth knowing

checkstyle.xml is not a documented Checkstyle convention — Checkstyle discovers nothing and takes its config as an argument. It is included because the name is unambiguous in practice, and alongside it sit two names that are documented: google_checks.xml and sun_checks.xml ship with the distribution, and config/checkstyle/ is the Gradle Checkstyle plugin’s documented default directory.

tsconfig.json is a compiler configuration, and the TypeScript handbook is explicit that it does not handle linting. It is tagged typechecker because it is nonetheless where a project’s type checking is actually configured (strict, noImplicitAny), which is the thing worth finding. jsconfig.json is the same file applied to a JavaScript project.

Filetypes, not just tags

Extensionless config dotfiles used to report Unknown. They now resolve on one principle: where a tool documents a single content format, map to that format; where several are accepted, the file gets its own name.

Resolves to its documented format	Gets its own name
.editorconfig, .flake8, .globalconfig, .pylintrc, pylintrc, .isort.cfg, .style.yapf → INI	.eslintrc → ESLintRC (JSON, YAML or JS)
.jshintrc → JSON	.prettierrc → Prettierrc (JSON or YAML)
staticcheck.conf → TOML	.stylelintrc → StylelintRC (JSON or YAML)
.rufo, Steepfile → Ruby (both are evaluated as Ruby)	.eslintignore, .prettierignore, .stylelintignore, .jshintignore, .yapfignore — gitignore-style pattern files
*.ruleset → XML

.cfg and .conf are mapped by basename rather than by extension, because both are used for arbitrary formats elsewhere — the same reasoning that already applied to setup.cfg.

Module extensions

Closing this gap also meant adding four extensions that were missing from EXT_FILETYPES altogether, and which are not linter-specific at all:

Extension	Language	Meaning
.mjs	JavaScript	always an ES module
.cjs	JavaScript	always CommonJS
.mts	TypeScript	TypeScript emitting an ES module
.cts	TypeScript	TypeScript emitting CommonJS

These exist because Node needs to know a file’s module system before parsing it, and .js alone does not say. Config authors reach for them to escape the "type" field in package.json, which is why eslint.config.mjs and .prettierrc.cjs are so common. Both pairs match GitHub Linguist, which types all four as programming.

Sources

Every convention above was checked against the tool’s own current documentation:

Tool	Source
ESLint	Configuration files (flat), v8 configuration files (eslintrc)
Prettier	Configuration file
Stylelint	Configure
Biome	Configure Biome
oxlint	Linter config
TypeScript	tsconfig.json
dprint	Setup and POSSIBLE_CONFIG_FILE_NAMES in resolve_main_config_path.rs
EditorConfig	editorconfig.org
Ruff	Configuration
Flake8	Configuring flake8
Pylint	Running pylint
mypy	The mypy configuration file
Pyright	Configuration
isort	Config files
yapf	README
Prospector	Profiles
golangci-lint	Configuration file
staticcheck	Configuration
RuboCop	Configuration
Standard	README
Reek	README
Rufo	README
erb_lint	README
Steep	README
Sorbet	CLI
Checkstyle	Gradle Checkstyle plugin
npm-groovy-lint	Documentation
Roslyn	Configuration files for code analysis rules
StyleCop	Configuration

Re-verifying

Config filenames change. ESLint replaced .eslintrc with flat config and dropped .eslintignore; Stylelint’s docs warn its legacy locations “may be removed in the future”. Legacy names are kept deliberately — a repository that still has .eslintrc.json is still a repository using ESLint.

When re-verifying, check each source above for new accepted extensions, and re-read the rejected list before adding anything in it.

Inventory

* marks a path fragment rather than a filename.

JavaScript, TypeScript and CSS

Tool	Role	Language tags	Config	Ignore
ESLint	linter	JavaScript, TypeScript	eslint.config.js, eslint.config.mjs, eslint.config.cjs, eslint.config.ts, eslint.config.mts, eslint.config.cts, .eslintrc, .eslintrc.js, .eslintrc.cjs, .eslintrc.yaml, .eslintrc.yml, .eslintrc.json	.eslintignore
Prettier	formatter	JavaScript, TypeScript, CSS	.prettierrc, .prettierrc.json, .prettierrc.yml, .prettierrc.yaml, .prettierrc.json5, .prettierrc.js, .prettierrc.mjs, .prettierrc.cjs, .prettierrc.ts, .prettierrc.mts, .prettierrc.cts, .prettierrc.toml, prettier.config.js, prettier.config.mjs, prettier.config.cjs, prettier.config.ts, prettier.config.mts, prettier.config.cts	.prettierignore
Stylelint	linter	CSS	stylelint.config.js, stylelint.config.mjs, stylelint.config.cjs, stylelint.config.ts, .stylelintrc, .stylelintrc.js, .stylelintrc.mjs, .stylelintrc.cjs, .stylelintrc.yml, .stylelintrc.yaml, .stylelintrc.json	.stylelintignore
Biome	linter, formatter	JavaScript, TypeScript, CSS	biome.json, biome.jsonc, .biome.json, .biome.jsonc	—
oxlint	linter	JavaScript, TypeScript	.oxlintrc.json, .oxlintrc.jsonc, oxlint.config.ts, oxlint.config.mts	—
dprint	formatter	JavaScript, TypeScript	dprint.json, dprint.jsonc, .dprint.json, .dprint.jsonc	—
JSHint	linter	JavaScript	.jshintrc	.jshintignore
TypeScript	typechecker	TypeScript, JavaScript	tsconfig.json, jsconfig.json	—
EditorConfig	formatter	(none)	.editorconfig	—

Python

Tool	Role	Language tags	Config	Ignore
Ruff	linter, formatter	Python	ruff.toml, .ruff.toml	—
Flake8	linter	Python	.flake8	—
Pylint	linter	Python	pylintrc, .pylintrc, pylintrc.toml, .pylintrc.toml	—
mypy	typechecker	Python	mypy.ini, .mypy.ini	—
Pyright	typechecker	Python	pyrightconfig.json	—
isort	formatter	Python	.isort.cfg	—
yapf	formatter	Python	.style.yapf	.yapfignore
Prospector	linter	Python	.prospector.yaml, .prospector.yml	—

Go

Tool	Role	Language tags	Config	Ignore
golangci-lint	linter	Go	.golangci.yml, .golangci.yaml, .golangci.toml, .golangci.json	—
staticcheck	linter	Go	staticcheck.conf	—

Ruby

Tool	Role	Language tags	Config	Ignore
RuboCop	linter, formatter	Ruby	.rubocop.yml	.rubocop_todo.yml
Standard	linter, formatter	Ruby	.standard.yml	.standard_todo.yml
Reek	linter	Ruby	.reek.yml	—
Rufo	formatter	Ruby	.rufo	—
erb_lint	linter	Ruby	.erb_lint.yml	—
Steep	typechecker	Ruby	steepfile	—
Sorbet	typechecker	Ruby	sorbet/*	—

Java

Tool	Role	Language tags	Config	Ignore
Checkstyle	linter	Java	checkstyle.xml, google_checks.xml, sun_checks.xml, config/checkstyle/*	—

Groovy

Tool	Role	Language tags	Config	Ignore
npm-groovy-lint	linter	Groovy	.groovylintrc.json, .groovylintrc.js, .groovylintrc.yml	—

C# and .NET

Tool	Role	Language tags	Config	Ignore
Roslyn	linter	C#, .NET	.globalconfig, *.ruleset	—
StyleCop	linter	C#, .NET	stylecop.json, .stylecop.json	—

SQL

Tool	Role	Language tags	Config	Ignore
SQLFluff	linter, formatter	SQL	.sqlfluff	.sqlfluffignore