Use swift-format for Swift file formatting

.github/workflows/swiftfmt.yml

@@ -0,0 +1,22 @@
+name: Swift format
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    paths:
+      - ".github/workflows/swiftfmt.yml"
+      - "**.swift"
+jobs:
+  swiftfmt:
+    name: Run swift format
+    runs-on: macos-latest
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v4
+        with:
+          show-progress: false
+
+    # Re-enable in follow-up PR that does the formatting.
+    #   - name: Check formating
+    #     run: ./swift-format.sh check

.swiftformatignore

@@ -0,0 +1 @@
+ios/Pods/**

README.md

@@ -41,6 +41,9 @@ dart format lib/ test/ -l 120
 
 In Android Studio, set the line length using Preferences -> Editor -> Code Style -> Dart -> Line length, set it to 120.  Enable auto-format with Preferences -> Languages & Frameworks -> Flutter -> Format code on save.
 
+`./swift-format.sh` can be used to format Swift code in the repo.
+
+Once `swift-format` supports ignoring directories (<https://github.com/swiftlang/swift-format/issues/870>), we can move to a method of running it more like what <https://calebhearth.com/swift-format-github-action> describes.
 
 # Release
 

swift-format.sh

@@ -0,0 +1,50 @@
+#!/bin/bash
+##===----------------------------------------------------------------------===##
+##
+## This source file is part of the Swift.org open source project
+##
+## Copyright (c) 2024 Apple Inc. and the Swift project authors
+## Licensed under Apache License v2.0 with Runtime Library Exception
+##
+## See https://swift.org/LICENSE.txt for license information
+## See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+##
+##===----------------------------------------------------------------------===##
+
+# Vendored from <https://github.com/swiftlang/github-workflows/blob/main/.github/workflows/scripts/check-swift-format.sh> while <https://github.com/swiftlang/swift-format/issues/870> is open.
+
+# This file has been modified to only check formatting, with no linting, and to require a `check` command flag to fail when formatting was performed.
+
+set -euo pipefail
+
+log() { printf -- "** %s\n" "$*" >&2; }
+error() { printf -- "** ERROR: %s\n" "$*" >&2; }
+fatal() { error "$@"; exit 1; }
+
+
+if [[ -f .swiftformatignore ]]; then
+    log "Found swiftformatignore file..."
+
+    log "Running swift format format..."
+    tr '\n' '\0' < .swiftformatignore| xargs -0 -I% printf '":(exclude)%" '| xargs git ls-files -z '*.swift' | xargs -0 xcrun swift-format --parallel --recursive --in-place
+
+    # log "Running swift format lint..."
+
+    # tr '\n' '\0' < .swiftformatignore | xargs -0 -I% printf '":(exclude)%" '| xargs git ls-files -z '*.swift' | xargs -0 swift format lint --strict --parallel
+else
+    log "Running swift format format..."
+    git ls-files -z '*.swift' | xargs -0 xcrun swift-format --parallel --recursive --in-place
+
+    # log "Running swift format lint..."
+
+    # git ls-files -z '*.swift' | xargs -0 swift format lint --strict --parallel
+fi
+
+
+if [ "${1-default}" = "check" ]; then
+log "Checking for modified files..."
+
+GIT_PAGER='' git diff --exit-code '*.swift'
+
+log "✅ Found no formatting issues."
+fi