Detect dprint config files

CHANGELOG.md

@@ -5,7 +5,7 @@ The format of this changelog is based on [Keep a Changelog](https://keepachangel
 ## [Unreleased]
 
 ### Added
- - Detection of linter, formatter and type checker configuration files and their ignore counterparts: 30 tools across JavaScript, TypeScript, CSS, Python, Go, Ruby, Java, Groovy, C#/.NET and SQL, covering 96 exact filenames. Every convention was verified against the tool's current official documentation; see [`docs/linter-detection-rules.md`](https://panopticas.io/linter-detection-rules) for the inventory, the sources, and the candidates that were investigated and rejected.
+ - Detection of linter, formatter and type checker configuration files and their ignore counterparts: 31 tools across JavaScript, TypeScript, CSS, Python, Go, Ruby, Java, Groovy, C#/.NET and SQL, covering 100 exact filenames. Every convention was verified against the tool's current official documentation; see [`docs/linter-detection-rules.md`](https://panopticas.io/linter-detection-rules) for the inventory, the sources, and the candidates that were investigated and rejected.
  - `LINTER_RULES` in `constants.py` is the single table describing those tools, expanded into the existing `METADATA_RULES` tables at import. `LINTER_ROLES` constrains the legal roles.
  - Two new role tags, `formatter` and `typechecker`, joining the existing `linter`. A tool may hold more than one — Ruff, Biome, RuboCop, Standard and SQLFluff all lint and format.
  - `.mjs` and `.cjs` now report as JavaScript, `.mts` and `.cts` as TypeScript. These were missing from the extension table entirely, so every file using them reported `Unknown` regardless of linters.

CLAUDE.md

@@ -47,7 +47,7 @@ Rules to follow when adding a product:
 
 ### Linter, Formatter and Type Checker Detection
 
-> **Before adding or changing a rule, read [`docs/linter-detection-rules.md`](docs/linter-detection-rules.md)** — the full inventory, the source confirming each convention, and the candidates already investigated and **rejected**. Eleven were rejected as wrong; re-adding one would mislabel repositories.
+> **Before adding or changing a rule, read [`docs/linter-detection-rules.md`](docs/linter-detection-rules.md)** — the full inventory, the source confirming each convention, and the candidates already investigated and **rejected**. Ten were rejected as wrong; re-adding one would mislabel repositories.
 
 `LINTER_RULES` in `constants.py` describes each tool once — its languages, its
 roles, and the files that identify it:

changes/2026-10-linter-detection.md

@@ -6,7 +6,7 @@
 ## What changed
 
 Panopticas now detects the configuration and exclusion files of code-quality
-tooling — 30 tools, 96 exact filenames — across JavaScript, TypeScript, CSS,
+tooling — 31 tools, 100 exact filenames — across JavaScript, TypeScript, CSS,
 Python, Go, Ruby, Java, Groovy, C#/.NET and SQL.
 
 Before this change the only linters detected were ESLint's flat config and
@@ -69,7 +69,7 @@ Every convention was verified against the tool's current official
 documentation before being added. The full evidence base, the sources, and the
 rejected candidates are in `docs/linter-detection-rules.md`.
 
-Eleven candidates were investigated and **rejected**, each of which would have
+Ten candidates were investigated and **rejected**, each of which would have
 been a wrong rule:
 
 - **revive** auto-discovers only `$HOME/revive.toml` — a user-level path, not
@@ -79,9 +79,17 @@ been a wrong rule:
 - **Black**, **StandardJS** and **Spotless** have no dedicated config file.
 - **gofmt**, **gofumpt** and **go vet** have no configuration at all.
 - **pycodestyle**'s dedicated file is user-level.
-- **dprint** is plausible but its filename list could not be confirmed.
 - Security scanners (Sonar, Bandit, Brakeman) are out of scope.
 
+**dprint** was initially in that list and has since been added. Its docs never
+enumerate the filenames it discovers, so the answer came from
+`POSSIBLE_CONFIG_FILE_NAMES` in dprint's
+`crates/dprint/src/configuration/resolve_main_config_path.rs`: exactly four
+names, walking up ancestor directories, no `config/` subdirectory. It also
+reads a user-level global config reusing the `dprint.jsonc` name, which does
+not disqualify it the way revive's user-level-only config did — dprint's four
+names are genuinely project-level.
+
 `pyproject.toml`, `setup.cfg`, `tox.ini` and `package.json` genuinely hold
 linter configuration, but which tool is inside is not knowable from the path,
 and detection here is path-based only. Tagging them would mislabel nearly

docs/linter-detection-rules.md

@@ -79,9 +79,25 @@ Each of these was investigated against the tool's current documentation and
 | **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`. |
-| **dprint** | Plausible (`dprint.json`), but the filename list could not be confirmed from the official docs. Left out pending verification — a missing rule is better than a wrong one. |
 | **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`](https://github.com/dprint/dprint/blob/main/crates/dprint/src/configuration/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
@@ -146,6 +162,7 @@ documentation:
 | Biome | [Configure Biome](https://biomejs.dev/guides/configure-biome/) |
 | oxlint | [Linter config](https://oxc.rs/docs/guide/usage/linter/config.html) |
 | TypeScript | [tsconfig.json](https://www.typescriptlang.org/docs/handbook/tsconfig-json.html) |
+| dprint | [Setup](https://dprint.dev/setup/) and `POSSIBLE_CONFIG_FILE_NAMES` in [resolve_main_config_path.rs](https://github.com/dprint/dprint/blob/main/crates/dprint/src/configuration/resolve_main_config_path.rs) |
 | EditorConfig | [editorconfig.org](https://editorconfig.org/) |
 | Ruff | [Configuration](https://docs.astral.sh/ruff/configuration/) |
 | Flake8 | [Configuring flake8](https://flake8.pycqa.org/en/latest/user/configuration.html) |
@@ -192,6 +209,7 @@ re-read the rejected list before adding anything in it.
 | **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` | — |
@@ -253,4 +271,4 @@ re-read the rejected list before adding anything in it.
 |---|---|---|---|---|
 | **SQLFluff** | linter, formatter | `SQL` | `.sqlfluff` | `.sqlfluffignore` |
 
-<!-- 30 tools, 96 exact filenames -->
+<!-- 31 tools, 100 exact filenames -->

src/panopticas/constants.py

@@ -401,6 +401,22 @@
         "config": [".oxlintrc.json", ".oxlintrc.jsonc", "oxlint.config.ts",
                    "oxlint.config.mts"],
     },
+    "dprint": {
+        # A plugin platform rather than one formatter; the TypeScript and
+        # JavaScript plugin is the flagship. It also formats JSON, Markdown,
+        # TOML and Dockerfiles, which is why only the two main languages are
+        # tagged.
+        "languages": ["JavaScript", "TypeScript"],
+        "roles": ["formatter"],
+        # POSSIBLE_CONFIG_FILE_NAMES in dprint's
+        # crates/dprint/src/configuration/resolve_main_config_path.rs. dprint
+        # also reads a user-level global config that reuses the dprint.jsonc
+        # name under ~/.config/dprint/ — not a repository artifact, and not
+        # matched by these rules, which are relative to the scanned tree.
+        "config": ["dprint.json", "dprint.jsonc", ".dprint.json",
+                   ".dprint.jsonc"],
+        # Exclusions are `excludes` globs inside the config; no ignore file.
+    },
     "JSHint": {
         "languages": ["JavaScript"],
         "roles": ["linter"],

tests/test_linter_detection.py

@@ -185,6 +185,24 @@ def test_biome_is_linter_and_formatter(self, filename):
     def test_oxlint_config(self, filename):
         assert {"linter", "oxlint"} <= tags_for(filename)
 
+    @pytest.mark.parametrize("filename", [
+        "dprint.json", "dprint.jsonc", ".dprint.json", ".dprint.jsonc",
+    ])
+    def test_dprint_config(self, filename):
+        # POSSIBLE_CONFIG_FILE_NAMES in dprint's
+        # crates/dprint/src/configuration/resolve_main_config_path.rs — the
+        # four names it auto-discovers, walking up ancestor directories.
+        assert {"formatter", "dprint", "config"} <= tags_for(filename)
+
+    def test_dprint_is_a_formatter_not_a_linter(self):
+        assert "linter" not in tags_for("dprint.json")
+
+    def test_dprint_has_no_ignore_file(self):
+        # Exclusions are `excludes` globs inside the config, as with
+        # golangci-lint. There is no .dprintignore to detect.
+        from panopticas.constants import LINTER_RULES
+        assert not LINTER_RULES["dprint"].get("ignore")
+
     def test_jshint_config_and_ignore(self):
         assert {"JavaScript", "linter", "JSHint", "config"} \
             <= tags_for(".jshintrc")