feat: support 'prettierd' in autofmt

prettierd is a daemon for prettier, allowing lower latency formats
see https://github.com/fsouza/prettierd

packages/autofmt/autofmt.js

@@ -1,5 +1,5 @@
 #!/usr/bin/env node
-// autofmt v1 by paper clover
+// autofmt v2 by paper clover
 // https://paperclover.dev/nix/config/src/branch/main/packages/autofmt/autofmt.js
 //
 // Different codebases use different formatters. Autofmt looks for project
@@ -25,6 +25,10 @@
 //     }
 //   },
 //
+// CHANGELOG
+// v2: added 'prettierd' as a supported formatter option.
+// v1: initial release
+//
 // @ts-nocheck
 
 // -- definitions --
@@ -72,6 +76,15 @@ const formatters = {
     cmd: ["deno", "fmt", "--", "$files"],
     stdin: (file) => ["deno", "fmt", "--ext", path.extname(file).slice(1), "-"],
   },
+  prettierd: {
+    // keep in mind that pretterd never exits.
+    // https://github.com/fsouza/prettierd/issues/645
+    languages: ["javascript", "markdown", "json", "yaml", "mdx", "html", "css"],
+    mustMatchFile: true,
+    files: { "node_modules/.bin/prettier": () => which("prettierd") },
+    cmd: null,
+    stdin: (file) => ["prettierd", file],
+  },
   prettier: {
     languages: ["javascript", "markdown", "json", "yaml", "mdx", "html", "css"],
     files: ["node_modules/.bin/prettier"],
@@ -91,7 +104,7 @@ const formatters = {
   "nixfmt-rfc-style": {
     languages: ["nix"],
     files: {
-      "flake.nix": (contents) => contents.includes("nixfmt"),
+      "flake.nix": ({ text }) => text.includes("nixfmt"),
     },
     cmd: ["nixfmt", "--", "$files"],
     stdin: (file) => ["nixfmt", `--filename=${file}`],
@@ -99,7 +112,7 @@ const formatters = {
   alejandra: {
     languages: ["nix"],
     files: {
-      "flake.nix": (contents) => contents.includes("alejandra"),
+      "flake.nix": ({ text }) => text.includes("alejandra"),
     },
     cmd: ["alejandra", "--", "$files"],
     stdin: () => ["alejandra"],
@@ -498,24 +511,31 @@ function pickFormatter(file) {
   return walkUp(dir, (x) => {
     const children = readDir(x);
     for (const fmt of order) {
+      if (formatters[fmt][stdio ? "stdin" : "cmd"] == null) continue;
+
       let matches = false;
       if (formatters[fmt].files === true) {
         matches = true;
       }
       if (!matches) {
         const filesToCheck = Array.isArray(formatters[fmt].files)
-          ? formatters[fmt].files.map((base) => ({ base, contents: true }))
+          ? formatters[fmt].files.map((base) => ({ base, check: true }))
           : Object.entries(formatters[fmt].files)
-            .map(([base, contents]) => ({ base, contents }));
+            .map(([base, check]) => ({ base, check }));
-        for (const { base, contents } of filesToCheck) {
+        for (const { base, check } of filesToCheck) {
           if (base.includes("/")) {
             matches = readDir(path.join(x, path.dirname(base))) //
               .includes(path.basename(base));
           } else {
             matches = children.includes(base);
           }
-          if (matches && typeof contents === "function") {
+          if (matches && typeof check === "function") {
-            matches = !!contents(fs.readFileSync(path.join(x, base), "utf-8"));
+            let text;
+            matches = !!check({
+              get text() {
+                return text ??= fs.readFileSync(path.join(x, base), "utf-8");
+              },
+            });
           }
         }
       }
@@ -526,7 +546,7 @@ function pickFormatter(file) {
         return formatterId;
       }
     }
-  }) ?? possible[0];
+  }) ?? possible.find((fmt) => !formatters[fmt].mustMatchFile);
 }
 
 /** @param dir {string} @param find {(x: string) => any} */
@@ -581,6 +601,29 @@ function readGitIgnore(dir) {
   }
 }
 
+/** @param {string} name @returns {string | null} */
+export function which(name) {
+  const paths =
+    process.env.PATH?.split(process.platform === "win32" ? ";" : ":") ?? [];
+  const exts = process.platform === "win32"
+    ? (process.env.PATHEXT?.split(";") ?? [".exe", ".cmd", ".bat", ".com"])
+    : [""];
+
+  for (const dir of paths) {
+    if (!dir) continue;
+    try {
+      const entries = readDir(dir);
+      for (const ext of exts) {
+        const target = name + ext;
+        if (entries.includes(target)) {
+          return dir + sep + target;
+        }
+      }
+    } catch {}
+  }
+  return null;
+}
+
 function escapeGlob(str) {
   return str.replace(/[\\*,{}]/g, "\\$&");
 }

packages/autofmt/default.nix

@@ -3,12 +3,13 @@ pkgs.writeShellApplication {
   name = "autofmt";
   runtimeInputs = with pkgs; [
     # include only a couple of formatters by default
+    clang-tools
     deno
-    nixfmt-rfc-style
     dprint
+    nixfmt-rfc-style
+    prettierd # autofmt only runs on a local build of prettier
     rustfmt
     zig
-    clang-tools
   ];
   text = ''exec ${pkgs.nodejs}/bin/node ${./autofmt.js} "$@"'';
 }