Format C# with dotnet format

.editorconfig

@@ -6,10 +6,16 @@ trim_trailing_whitespace=true
 [makefile]
 indent_style=tab
 
-[*.{gradle,java,kt,kts,sh,xml,yaml,yml}]
+[*.{cs,gradle,java,kt,kts,sh,xml,yaml,yml}]
 indent_size=2
 max_line_length=100
 
+; https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/style-rules/
+; https://google.github.io/styleguide/csharp-style.html#whitespace-rules
+[*.cs]
+csharp_new_line_before_open_brace = none
+dotnet_diagnostic.IDE0011.severity = error
+
 [*.{js,jsx,ts,tsx}]
 indent_size=2
 max_line_length=80

Dockerfile

@@ -40,6 +40,7 @@ apk add --no-cache --virtual .build-deps \
   py3-pip \
   python3-dev
 apk add --no-cache \
+  dotnet8-sdk \
   libxslt \
   nodejs \
   python3

Makefile

@@ -48,7 +48,7 @@ shell:
 # Runs tests
 .PHONY: test
 test:
-	docker run --rm -v "$${PWD}/test:/test" "$$(docker build --network=host -q .)" sh -c \
+	docker run --rm --init -v "$${PWD}/test:/test" "$$(docker build --network=host -q .)" sh -c \
 		'cd /tmp \
 			&& cp -r /test/before actual \
 			&& cp -r /test/after expected \

README.md

@@ -17,6 +17,7 @@ This repo currently contains a single [pre-commit](https://pre-commit.com/) hook
 - [xsltproc](http://www.xmlsoft.org/xslt/xsltproc.html) from libxslt v10139 for XML
 - [terraform fmt](https://github.com/hashicorp/terraform) v1.9.8 for Terraform
 - [ClangFormat](https://clang.llvm.org/docs/ClangFormat.html) v18.1.8 for C++, Protobuf
+- [dotnet format](https://docs.microsoft.com/en-us/dotnet/core/tools/dotnet-format) v8.0.111 for C#
 - [SVGO](https://github.com/svg/svgo) v3.3.2 for SVG
 - [Taplo](https://taplo.tamasfe.dev/) v0.9.3 for TOML
 - Custom regex transformations (basically [sed](https://en.wikipedia.org/wiki/Sed)), for example:

entry.ts

@@ -1,7 +1,8 @@
 #!/usr/bin/env node
 
 import { exec } from "child_process";
-import { createReadStream, readFile, writeFile } from "fs";
+import { createReadStream } from "fs";
+import { readFile, unlink, writeFile } from "fs/promises";
 import { createInterface } from "readline";
 
 /**
@@ -49,37 +50,32 @@ const run = (...args: string[]) =>
 export const isTruthy = <T>(value: T): value is NonNullable<T> => !!value;
 
 /** Reads a file, transforms its contents, and writes the result if different */
-const transformFile = (path: string, transform: (before: string) => string) =>
-  new Promise<void>((resolve, reject) => {
-    readFile(path, "utf8", (err, data) => {
-      // File unreadable
-      if (err) {
-        reject(err);
-        return;
-      }
-
-      // File empty
-      if (data === "") {
-        resolve();
-        return;
-      }
+const transformFile = async (
+  path: string,
+  transform: (before: string) => string,
+) => {
+  const data = await readFile(path, "utf8");
+
+  // File empty
+  if (data === "") {
+    return;
+  }
 
-      // File unmodified
-      const after = transform(data);
-      if (data === after) {
-        resolve();
-        return;
-      }
+  // File unmodified
+  const after = transform(data);
+  if (data === after) {
+    return;
+  }
 
-      // File modified
-      writeFile(path, after, "utf8", err => (err ? reject(err) : resolve()));
-    });
-  });
+  // File modified
+  await writeFile(path, after, "utf8");
+};
 
 const enum HookName {
   Autoflake = "autoflake",
   Black = "Black",
   ClangFormat = "ClangFormat",
+  DotnetFormat = "dotnet format",
   EsLint = "ESLint",
   Gofmt = "gofmt",
   GoogleJavaFormat = "google-java-format",
@@ -191,6 +187,46 @@ const HOOKS: Record<HookName, LockableHook> = {
     include: /\.(cpp|proto$)/,
     runAfter: [HookName.Sed],
   }),
+  [HookName.DotnetFormat]: createLockableHook({
+    action: async sources => {
+      // Create project file
+      const projectFile = `dotnet-format-${Math.random()}.csproj`;
+      await writeFile(
+        projectFile,
+        `<Project Sdk="Microsoft.NET.Sdk">
+          <PropertyGroup>
+            <EnableDefaultItems>false</EnableDefaultItems>
+            <TargetFramework>net8.0</TargetFramework>
+          </PropertyGroup>
+          <ItemGroup>
+            ${sources.map(s => `<Compile Include="${s}" />`).join("")}
+          </ItemGroup>
+        </Project>`,
+      );
+      try {
+        await run(
+          "dotnet",
+          "format",
+          "style",
+          projectFile,
+          "--verbosity",
+          "quiet",
+        );
+        await run(
+          "dotnet",
+          "format",
+          "whitespace",
+          projectFile,
+          "--verbosity",
+          "quiet",
+        );
+      } finally {
+        await unlink(projectFile);
+      }
+    },
+    include: /\.cs$/,
+    runAfter: [HookName.Sed],
+  }),
   [HookName.EsLint]: createLockableHook({
     action: async sources => {
       try {

test/after/hello.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Collections.Generic;
+
+namespace HelloWorld {
+  public class Program {
+    public static void Main(string[] args) {
+      Console.WriteLine("Hello, World!");
+      var numbers = new List<int> { 1, 2, 3 };
+      foreach (var number in numbers) {
+        Console.WriteLine($"Number: {number}");
+      }
+    }
+  }
+}

test/before/hello.cs

@@ -0,0 +1,14 @@
+ using System  ;
+using System.Collections.Generic;
+
+namespace HelloWorld{
+  public class Program
+{public static void Main(string[]args)
+{
+Console.WriteLine("Hello, World!");
+var  numbers=new List<int>{1,2,3};
+foreach (var number in numbers)
+Console.WriteLine($"Number: {number}");
+}
+}
+}