feat: auto-discover config file (#13313)

14 files changed, 313 insertions, 126 deletions

diff --git a/cli/config_file.rs b/cli/config_file.rs
index f18e56fc1..3ca00b0f4 100644
--- a/cli/config_file.rs
+++ b/cli/config_file.rs
@@ -18,8 +18,10 @@ use deno_core::serde_json::Value;
 use deno_core::ModuleSpecifier;
 use std::collections::BTreeMap;
 use std::collections::HashMap;
+use std::collections::HashSet;
 use std::fmt;
 use std::path::Path;
+use std::path::PathBuf;
 
 pub(crate) type MaybeImportsResult =
   Result<Option<Vec<(ModuleSpecifier, Vec<String>)>>, AnyError>;
@@ -156,6 +158,61 @@ pub const IGNORED_RUNTIME_COMPILER_OPTIONS: &[&str] = &[
   "watch",
 ];
 
+/// Filenames that Deno will recognize when discovering config.
+const CONFIG_FILE_NAMES: [&str; 2] = ["deno.json", "deno.jsonc"];
+
+pub fn discover(flags: &crate::Flags) -> Result<Option<ConfigFile>, AnyError> {
+  if let Some(config_path) = flags.config_path.as_ref() {
+    Ok(Some(ConfigFile::read(config_path)?))
+  } else {
+    let mut checked = HashSet::new();
+    for f in flags.config_path_args() {
+      if let Some(cf) = discover_from(&f, &mut checked)? {
+        return Ok(Some(cf));
+      }
+    }
+
+    // From CWD walk up to root looking for deno.json or deno.jsonc
+    let cwd = std::env::current_dir()?;
+    discover_from(&cwd, &mut checked)
+  }
+}
+
+pub fn discover_from(
+  start: &Path,
+  checked: &mut HashSet<PathBuf>,
+) -> Result<Option<ConfigFile>, AnyError> {
+  for ancestor in start.ancestors() {
+    if checked.insert(ancestor.to_path_buf()) {
+      for config_filename in CONFIG_FILE_NAMES {
+        let f = ancestor.join(config_filename);
+        match ConfigFile::read(f) {
+          Ok(cf) => {
+            return Ok(Some(cf));
+          }
+          Err(e) => {
+            if let Some(ioerr) = e.downcast_ref::<std::io::Error>() {
+              use std::io::ErrorKind::*;
+              match ioerr.kind() {
+                InvalidInput | PermissionDenied | NotFound => {
+                  // ok keep going
+                }
+                _ => {
+                  return Err(e); // Unknown error. Stop.
+                }
+              }
+            } else {
+              return Err(e); // Parse error or something else. Stop.
+            }
+          }
+        }
+      }
+    }
+  }
+  // No config file found.
+  Ok(None)
+}
+
 /// A function that works like JavaScript's `Object.assign()`.
 pub fn json_merge(a: &mut Value, b: &Value) {
   match (a, b) {
@@ -823,4 +880,38 @@ mod tests {
     }));
     assert_eq!(tsconfig1.as_bytes(), tsconfig2.as_bytes());
   }
+
+  #[test]
+  fn discover_from_success() {
+    // testdata/fmt/deno.jsonc exists
+    let testdata = test_util::testdata_path();
+    let c_md = testdata.join("fmt/with_config/subdir/c.md");
+    let mut checked = HashSet::new();
+    let config_file = discover_from(&c_md, &mut checked).unwrap().unwrap();
+    assert!(checked.contains(c_md.parent().unwrap()));
+    assert!(!checked.contains(&testdata));
+    let fmt_config = config_file.to_fmt_config().unwrap().unwrap();
+    let expected_exclude = ModuleSpecifier::from_file_path(
+      testdata.join("fmt/with_config/subdir/b.ts"),
+    )
+    .unwrap();
+    assert_eq!(fmt_config.files.exclude, vec![expected_exclude]);
+
+    // Now add all ancestors of testdata to checked.
+    for a in testdata.ancestors() {
+      checked.insert(a.to_path_buf());
+    }
+
+    // If we call discover_from again starting at testdata, we ought to get None.
+    assert!(discover_from(&testdata, &mut checked).unwrap().is_none());
+  }
+
+  #[test]
+  fn discover_from_malformed() {
+    let testdata = test_util::testdata_path();
+    let d = testdata.join("malformed_config/");
+    let mut checked = HashSet::new();
+    let err = discover_from(&d, &mut checked).unwrap_err();
+    assert!(err.to_string().contains("Unable to parse config file"));
+  }
 }
diff --git a/cli/flags.rs b/cli/flags.rs
index 854b54416..8b308658d 100644
--- a/cli/flags.rs
+++ b/cli/flags.rs
@@ -361,6 +361,28 @@ impl Flags {
 
     args
   }
+
+  /// Extract path arguments for config search paths.
+  pub fn config_path_args(&self) -> Vec<PathBuf> {
+    use DenoSubcommand::*;
+    if let Fmt(FmtFlags { files, .. }) = &self.subcommand {
+      files.clone()
+    } else if let Lint(LintFlags { files, .. }) = &self.subcommand {
+      files.clone()
+    } else if let Run(RunFlags { script }) = &self.subcommand {
+      if let Ok(module_specifier) = deno_core::resolve_url_or_path(script) {
+        if let Ok(p) = module_specifier.to_file_path() {
+          vec![p]
+        } else {
+          vec![]
+        }
+      } else {
+        vec![]
+      }
+    } else {
+      vec![]
+    }
+  }
 }
 
 impl From<Flags> for PermissionsOptions {
@@ -4628,4 +4650,30 @@ mod tests {
       }
     );
   }
+
+  #[test]
+  fn test_config_path_args() {
+    let flags = flags_from_vec(svec!["deno", "run", "foo.js"]).unwrap();
+    assert_eq!(
+      flags.config_path_args(),
+      vec![std::env::current_dir().unwrap().join("foo.js")]
+    );
+
+    let flags =
+      flags_from_vec(svec!["deno", "lint", "dir/a.js", "dir/b.js"]).unwrap();
+    assert_eq!(
+      flags.config_path_args(),
+      vec![PathBuf::from("dir/a.js"), PathBuf::from("dir/b.js")]
+    );
+
+    let flags = flags_from_vec(svec!["deno", "lint"]).unwrap();
+    assert!(flags.config_path_args().is_empty());
+
+    let flags =
+      flags_from_vec(svec!["deno", "fmt", "dir/a.js", "dir/b.js"]).unwrap();
+    assert_eq!(
+      flags.config_path_args(),
+      vec![PathBuf::from("dir/a.js"), PathBuf::from("dir/b.js")]
+    );
+  }
 }
diff --git a/cli/fs_util.rs b/cli/fs_util.rs
index 7290d3696..fbdcdc81a 100644
--- a/cli/fs_util.rs
+++ b/cli/fs_util.rs
@@ -139,34 +139,6 @@ pub fn is_supported_ext(path: &Path) -> bool {
   }
 }
 
-/// This function is similar to is_supported_ext but adds additional extensions
-/// supported by `deno fmt`.
-pub fn is_supported_ext_fmt(path: &Path) -> bool {
-  if let Some(ext) = get_extension(path) {
-    matches!(
-      ext.as_str(),
-      "ts"
-        | "tsx"
-        | "js"
-        | "jsx"
-        | "mjs"
-        | "mts"
-        | "cjs"
-        | "cts"
-        | "json"
-        | "jsonc"
-        | "md"
-        | "mkd"
-        | "mkdn"
-        | "mdwn"
-        | "mdown"
-        | "markdown"
-    )
-  } else {
-    false
-  }
-}
-
 /// Checks if the path has a basename and extension Deno supports for tests.
 pub fn is_supported_test_path(path: &Path) -> bool {
   if let Some(name) = path.file_stem() {
@@ -459,45 +431,10 @@ mod tests {
   }
 
   #[test]
-  fn test_is_supported_ext_fmt() {
-    assert!(!is_supported_ext_fmt(Path::new("tests/subdir/redirects")));
-    assert!(is_supported_ext_fmt(Path::new("README.md")));
-    assert!(is_supported_ext_fmt(Path::new("readme.MD")));
-    assert!(is_supported_ext_fmt(Path::new("readme.mkd")));
-    assert!(is_supported_ext_fmt(Path::new("readme.mkdn")));
-    assert!(is_supported_ext_fmt(Path::new("readme.mdwn")));
-    assert!(is_supported_ext_fmt(Path::new("readme.mdown")));
-    assert!(is_supported_ext_fmt(Path::new("readme.markdown")));
-    assert!(is_supported_ext_fmt(Path::new("lib/typescript.d.ts")));
-    assert!(is_supported_ext_fmt(Path::new("testdata/001_hello.js")));
-    assert!(is_supported_ext_fmt(Path::new("testdata/002_hello.ts")));
-    assert!(is_supported_ext_fmt(Path::new("foo.jsx")));
-    assert!(is_supported_ext_fmt(Path::new("foo.tsx")));
-    assert!(is_supported_ext_fmt(Path::new("foo.TS")));
-    assert!(is_supported_ext_fmt(Path::new("foo.TSX")));
-    assert!(is_supported_ext_fmt(Path::new("foo.JS")));
-    assert!(is_supported_ext_fmt(Path::new("foo.JSX")));
-    assert!(is_supported_ext_fmt(Path::new("foo.mjs")));
-    assert!(is_supported_ext_fmt(Path::new("foo.mts")));
-    assert!(is_supported_ext_fmt(Path::new("foo.cjs")));
-    assert!(is_supported_ext_fmt(Path::new("foo.cts")));
-    assert!(!is_supported_ext_fmt(Path::new("foo.mjsx")));
-    assert!(is_supported_ext_fmt(Path::new("foo.jsonc")));
-    assert!(is_supported_ext_fmt(Path::new("foo.JSONC")));
-    assert!(is_supported_ext_fmt(Path::new("foo.json")));
-    assert!(is_supported_ext_fmt(Path::new("foo.JsON")));
-  }
-
-  #[test]
   fn test_is_supported_test_ext() {
     assert!(!is_supported_test_ext(Path::new("tests/subdir/redirects")));
     assert!(is_supported_test_ext(Path::new("README.md")));
     assert!(is_supported_test_ext(Path::new("readme.MD")));
-    assert!(is_supported_ext_fmt(Path::new("readme.mkd")));
-    assert!(is_supported_ext_fmt(Path::new("readme.mkdn")));
-    assert!(is_supported_ext_fmt(Path::new("readme.mdwn")));
-    assert!(is_supported_ext_fmt(Path::new("readme.mdown")));
-    assert!(is_supported_ext_fmt(Path::new("readme.markdown")));
     assert!(is_supported_test_ext(Path::new("lib/typescript.d.ts")));
     assert!(is_supported_test_ext(Path::new("testdata/001_hello.js")));
     assert!(is_supported_test_ext(Path::new("testdata/002_hello.ts")));
diff --git a/cli/lsp/language_server.rs b/cli/lsp/language_server.rs
index 5b04b8a25..fc0ae1312 100644
--- a/cli/lsp/language_server.rs
+++ b/cli/lsp/language_server.rs
@@ -320,7 +320,23 @@ impl Inner {
       }
     }
 
-    Ok(None)
+    // Auto-discover config
+
+    // It is possible that root_uri is not set, for example when having a single
+    // file open and not a workspace.  In those situations we can't
+    // automatically discover the configuration
+    if let Some(root_uri) = maybe_root_uri {
+      let root_path = root_uri.to_file_path().unwrap();
+      let mut checked = std::collections::HashSet::new();
+      let maybe_config =
+        crate::config_file::discover_from(&root_path, &mut checked)?;
+      Ok(maybe_config.map(|c| {
+        lsp_log!("  Auto-resolved configuration file: \"{}\"", c.specifier);
+        c
+      }))
+    } else {
+      Ok(None)
+    }
   }
 
   fn is_diagnosable(&self, specifier: &ModuleSpecifier) -> bool {
diff --git a/cli/proc_state.rs b/cli/proc_state.rs
index 6e8507810..13a17b8fb 100644
--- a/cli/proc_state.rs
+++ b/cli/proc_state.rs
@@ -207,12 +207,7 @@ impl ProcState {
       None
     };
 
-    let maybe_config_file =
-      if let Some(config_path) = flags.config_path.as_ref() {
-        Some(ConfigFile::read(config_path)?)
-      } else {
-        None
-      };
+    let maybe_config_file = crate::config_file::discover(&flags)?;
 
     let maybe_import_map: Option<Arc<ImportMap>> =
       match flags.import_map_path.as_ref() {
diff --git a/cli/tests/integration/fmt_tests.rs b/cli/tests/integration/fmt_tests.rs
index 18743fb00..bb4c8b451 100644
--- a/cli/tests/integration/fmt_tests.rs
+++ b/cli/tests/integration/fmt_tests.rs
@@ -177,13 +177,18 @@ itest!(fmt_stdin_check_not_formatted {
 });
 
 itest!(fmt_with_config {
-  args: "fmt --config fmt/deno.jsonc fmt/fmt_with_config/",
+  args: "fmt --config fmt/with_config/deno.jsonc fmt/with_config/subdir",
+  output: "fmt/fmt_with_config.out",
+});
+
+itest!(fmt_with_config_default {
+  args: "fmt fmt/with_config/subdir",
   output: "fmt/fmt_with_config.out",
 });
 
 // Check if CLI flags take precedence
 itest!(fmt_with_config_and_flags {
-  args: "fmt --config fmt/deno.jsonc --ignore=fmt/fmt_with_config/a.ts,fmt/fmt_with_config/b.ts",
+  args: "fmt --config fmt/with_config/deno.jsonc --ignore=fmt/with_config/subdir/a.ts,fmt/with_config/subdir/b.ts",
   output: "fmt/fmt_with_config_and_flags.out",
 });
 
diff --git a/cli/tests/integration/lsp_tests.rs b/cli/tests/integration/lsp_tests.rs
index 21894f7e8..c992ca4cb 100644
--- a/cli/tests/integration/lsp_tests.rs
+++ b/cli/tests/integration/lsp_tests.rs
@@ -55,12 +55,12 @@ where
   client
     .write_response(
       id,
-      json!({
+      json!([{
         "enable": true,
         "codeLens": {
           "test": true
         }
-      }),
+      }]),
     )
     .unwrap();
 
@@ -564,7 +564,7 @@ fn lsp_hover_disabled() {
   let (id, method, _) = client.read_request::<Value>().unwrap();
   assert_eq!(method, "workspace/configuration");
   client
-    .write_response(id, json!({ "enable": false }))
+    .write_response(id, json!([{ "enable": false }]))
     .unwrap();
 
   let (maybe_res, maybe_err) = client
@@ -814,7 +814,7 @@ fn lsp_hover_closed_document() {
   let (id, method, _) = client.read_request::<Value>().unwrap();
   assert_eq!(method, "workspace/configuration");
   client
-    .write_response(id, json!({ "enable": true }))
+    .write_response(id, json!([{ "enable": true }]))
     .unwrap();
 
   client
@@ -833,7 +833,7 @@ fn lsp_hover_closed_document() {
   let (id, method, _) = client.read_request::<Value>().unwrap();
   assert_eq!(method, "workspace/configuration");
   client
-    .write_response(id, json!({ "enable": true }))
+    .write_response(id, json!([{ "enable": true }]))
     .unwrap();
 
   let (method, _) = client.read_notification::<Value>().unwrap();
@@ -1543,6 +1543,58 @@ fn lsp_format_exclude_with_config() {
 }
 
 #[test]
+fn lsp_format_exclude_default_config() {
+  let temp_dir = TempDir::new().unwrap();
+  let workspace_root = temp_dir.path().canonicalize().unwrap();
+  let mut params: lsp::InitializeParams =
+    serde_json::from_value(load_fixture("initialize_params.json")).unwrap();
+  let deno_jsonc =
+    serde_json::to_vec_pretty(&load_fixture("deno.fmt.exclude.jsonc")).unwrap();
+  fs::write(workspace_root.join("deno.jsonc"), deno_jsonc).unwrap();
+
+  params.root_uri = Some(Url::from_file_path(workspace_root.clone()).unwrap());
+
+  let deno_exe = deno_exe_path();
+  let mut client = LspClient::new(&deno_exe).unwrap();
+  client
+    .write_request::<_, _, Value>("initialize", params)
+    .unwrap();
+
+  let file_uri =
+    ModuleSpecifier::from_file_path(workspace_root.join("ignored.ts"))
+      .unwrap()
+      .to_string();
+  did_open(
+    &mut client,
+    json!({
+      "textDocument": {
+        "uri": file_uri,
+        "languageId": "typescript",
+        "version": 1,
+        "text": "function   myFunc(){}"
+      }
+    }),
+  );
+  let (maybe_res, maybe_err) = client
+    .write_request(
+      "textDocument/formatting",
+      json!({
+        "textDocument": {
+          "uri": file_uri
+        },
+        "options": {
+          "tabSize": 2,
+          "insertSpaces": true
+        }
+      }),
+    )
+    .unwrap();
+  assert!(maybe_err.is_none());
+  assert_eq!(maybe_res, Some(json!(null)));
+  shutdown(&mut client);
+}
+
+#[test]
 fn lsp_large_doc_changes() {
   let mut client = init("initialize_params.json");
   did_open(&mut client, load_fixture("did_open_params_large.json"));
@@ -2085,12 +2137,12 @@ fn lsp_code_lens_test_disabled() {
   client
     .write_response(
       id,
-      json!({
+      json!([{
         "enable": true,
         "codeLens": {
           "test": false
         }
-      }),
+      }]),
     )
     .unwrap();
 
@@ -2467,7 +2519,7 @@ fn lsp_code_actions_deno_cache() {
   let (id, method, _) = client.read_request::<Value>().unwrap();
   assert_eq!(method, "workspace/configuration");
   client
-    .write_response(id, json!({ "enable": true }))
+    .write_response(id, json!([{ "enable": true }]))
     .unwrap();
   let (method, _) = client.read_notification::<Value>().unwrap();
   assert_eq!(method, "textDocument/publishDiagnostics");
@@ -2641,7 +2693,7 @@ fn lsp_code_actions_deadlock() {
   let (id, method, _) = client.read_request::<Value>().unwrap();
   assert_eq!(method, "workspace/configuration");
   client
-    .write_response(id, json!({ "enable": true }))
+    .write_response(id, json!([{ "enable": true }]))
     .unwrap();
   let (maybe_res, maybe_err) = client
     .write_request::<_, _, Value>(
@@ -3301,7 +3353,7 @@ fn lsp_diagnostics_deno_types() {
   let (id, method, _) = client.read_request::<Value>().unwrap();
   assert_eq!(method, "workspace/configuration");
   client
-    .write_response(id, json!({ "enable": true }))
+    .write_response(id, json!([{ "enable": true }]))
     .unwrap();
   let (maybe_res, maybe_err) = client
     .write_request::<_, _, Value>(
@@ -3354,34 +3406,20 @@ fn lsp_diagnostics_refresh_dependents() {
       },
     }),
   );
-  client
-    .write_notification(
-      "textDocument/didOpen",
-      json!({
-        "textDocument": {
-          "uri": "file:///a/file_02.ts",
-          "languageId": "typescript",
-          "version": 1,
-          "text": "import { a, b } from \"./file_01.ts\";\n\nconsole.log(a, b);\n"
-        }
-      }),
-    )
-    .unwrap();
-
-  let (id, method, _) = client.read_request::<Value>().unwrap();
-  assert_eq!(method, "workspace/configuration");
-  client
-    .write_response(id, json!({ "enable": false }))
-    .unwrap();
-  let (method, _) = client.read_notification::<Value>().unwrap();
-  assert_eq!(method, "textDocument/publishDiagnostics");
-  let (method, _) = client.read_notification::<Value>().unwrap();
-  assert_eq!(method, "textDocument/publishDiagnostics");
-  let (method, maybe_params) = client.read_notification::<Value>().unwrap();
-  assert_eq!(method, "textDocument/publishDiagnostics");
+  let diagnostics = did_open(
+    &mut client,
+    json!({
+      "textDocument": {
+        "uri": "file:///a/file_02.ts",
+        "languageId": "typescript",
+        "version": 1,
+        "text": "import { a, b } from \"./file_01.ts\";\n\nconsole.log(a, b);\n"
+      }
+    }),
+  );
   assert_eq!(
-    maybe_params,
-    Some(json!({
+    json!(diagnostics[2]),
+    json!({
       "uri": "file:///a/file_02.ts",
       "diagnostics": [
         {
@@ -3402,7 +3440,7 @@ fn lsp_diagnostics_refresh_dependents() {
         }
       ],
       "version": 1
-    }))
+    })
   );
   client
     .write_notification(
diff --git a/cli/tests/testdata/fmt/deno.jsonc b/cli/tests/testdata/fmt/deno.jsonc
deleted file mode 100644
index 9c330d34a..000000000
--- a/cli/tests/testdata/fmt/deno.jsonc
+++ /dev/null
@@ -1,15 +0,0 @@
-{
-  "fmt": {
-    "files": {
-      "include": ["fmt_with_config/"],
-      "exclude": ["fmt_with_config/b.ts"]
-    },
-    "options": {
-      "useTabs": true,
-      "lineWidth": 40,
-      "indentWidth": 8,
-      "singleQuote": true,
-      "proseWrap": "always"
-    }
-  }
-}
diff --git a/cli/tests/testdata/fmt/with_config/deno.jsonc b/cli/tests/testdata/fmt/with_config/deno.jsonc
new file mode 100644
index 000000000..3b9474e64
--- /dev/null
+++ b/cli/tests/testdata/fmt/with_config/deno.jsonc
@@ -0,0 +1,19 @@
+{
+	"fmt": {
+		"files": {
+			"include": [
+				"./subdir/"
+			],
+			"exclude": [
+				"./subdir/b.ts"
+			]
+		},
+		"options": {
+			"useTabs": true,
+			"lineWidth": 40,
+			"indentWidth": 8,
+			"singleQuote": true,
+			"proseWrap": "always"
+		}
+	}
+}
diff --git a/cli/tests/testdata/fmt/fmt_with_config/a.ts b/cli/tests/testdata/fmt/with_config/subdir/a.ts
index 50db0d2e1..50db0d2e1 100644
--- a/cli/tests/testdata/fmt/fmt_with_config/a.ts
+++ b/cli/tests/testdata/fmt/with_config/subdir/a.ts
diff --git a/cli/tests/testdata/fmt/fmt_with_config/b.ts b/cli/tests/testdata/fmt/with_config/subdir/b.ts
index 840198d89..840198d89 100644
--- a/cli/tests/testdata/fmt/fmt_with_config/b.ts
+++ b/cli/tests/testdata/fmt/with_config/subdir/b.ts
diff --git a/cli/tests/testdata/fmt/fmt_with_config/c.md b/cli/tests/testdata/fmt/with_config/subdir/c.md
index 012f7e3d4..012f7e3d4 100644
--- a/cli/tests/testdata/fmt/fmt_with_config/c.md
+++ b/cli/tests/testdata/fmt/with_config/subdir/c.md
diff --git a/cli/tests/testdata/malformed_config/deno.json b/cli/tests/testdata/malformed_config/deno.json
new file mode 100644
index 000000000..60df56527
--- /dev/null
+++ b/cli/tests/testdata/malformed_config/deno.json
@@ -0,0 +1 @@
+not a json file
diff --git a/cli/tools/fmt.rs b/cli/tools/fmt.rs
index 1d48e7025..3044f13d5 100644
--- a/cli/tools/fmt.rs
+++ b/cli/tools/fmt.rs
@@ -16,7 +16,7 @@ use crate::file_watcher;
 use crate::file_watcher::ResolutionResult;
 use crate::flags::FmtFlags;
 use crate::fs_util::specifier_to_file_path;
-use crate::fs_util::{collect_files, get_extension, is_supported_ext_fmt};
+use crate::fs_util::{collect_files, get_extension};
 use crate::text_encoding;
 use deno_ast::ParsedSource;
 use deno_core::anyhow::bail;
@@ -591,3 +591,55 @@ where
     Ok(())
   }
 }
+
+/// This function is similar to is_supported_ext but adds additional extensions
+/// supported by `deno fmt`.
+fn is_supported_ext_fmt(path: &Path) -> bool {
+  if let Some(ext) = get_extension(path) {
+    matches!(
+      ext.as_str(),
+      "ts"
+        | "tsx"
+        | "js"
+        | "jsx"
+        | "mjs"
+        | "json"
+        | "jsonc"
+        | "md"
+        | "mkd"
+        | "mkdn"
+        | "mdwn"
+        | "mdown"
+        | "markdown"
+    )
+  } else {
+    false
+  }
+}
+
+#[test]
+fn test_is_supported_ext_fmt() {
+  assert!(!is_supported_ext_fmt(Path::new("tests/subdir/redirects")));
+  assert!(is_supported_ext_fmt(Path::new("README.md")));
+  assert!(is_supported_ext_fmt(Path::new("readme.MD")));
+  assert!(is_supported_ext_fmt(Path::new("readme.mkd")));
+  assert!(is_supported_ext_fmt(Path::new("readme.mkdn")));
+  assert!(is_supported_ext_fmt(Path::new("readme.mdwn")));
+  assert!(is_supported_ext_fmt(Path::new("readme.mdown")));
+  assert!(is_supported_ext_fmt(Path::new("readme.markdown")));
+  assert!(is_supported_ext_fmt(Path::new("lib/typescript.d.ts")));
+  assert!(is_supported_ext_fmt(Path::new("testdata/001_hello.js")));
+  assert!(is_supported_ext_fmt(Path::new("testdata/002_hello.ts")));
+  assert!(is_supported_ext_fmt(Path::new("foo.jsx")));
+  assert!(is_supported_ext_fmt(Path::new("foo.tsx")));
+  assert!(is_supported_ext_fmt(Path::new("foo.TS")));
+  assert!(is_supported_ext_fmt(Path::new("foo.TSX")));
+  assert!(is_supported_ext_fmt(Path::new("foo.JS")));
+  assert!(is_supported_ext_fmt(Path::new("foo.JSX")));
+  assert!(is_supported_ext_fmt(Path::new("foo.mjs")));
+  assert!(!is_supported_ext_fmt(Path::new("foo.mjsx")));
+  assert!(is_supported_ext_fmt(Path::new("foo.jsonc")));
+  assert!(is_supported_ext_fmt(Path::new("foo.JSONC")));
+  assert!(is_supported_ext_fmt(Path::new("foo.json")));
+  assert!(is_supported_ext_fmt(Path::new("foo.JsON")));
+}