Merge pull request swiftlang#136 from google/colordiff

Add a script to view before/after formatting diffs for debugging.

Author: dabelknap

Scripts/format-diff.sh

@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+#===----------------------------------------------------------------------===#
+#
+# This source file is part of the Swift Formatter open source project.
+#
+# Copyright (c) 2018 Apple Inc. and the Swift Formatter project authors
+# Licensed under Apache License v2.0
+#
+# See LICENSE.txt for license information
+# See CONTRIBUTORS.txt for the list of Swift Formatter project authors
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+#===----------------------------------------------------------------------===#
+
+# SYNOPSIS
+#   format-diff.sh FILE [OPTION]...
+#
+# DESCRIPTION
+#   Runs the formatter and displays a side-by-side diff of the original file
+#   and the formatted results. The script will use `colordiff` for the output
+#   if it is present; otherwise, regular `diff` will be used.
+#
+#   The first argument to this script must be the `.swift` source file to be
+#   formatted. Any remaining arguments after that will be passed directly to
+#   `swift-format`.
+
+set -euo pipefail
+
+SRCFILE="$1" ; shift
+
+# Use `colordiff` if it's present; otherwise, fall back to `diff`.
+if which colordiff >/dev/null ; then
+  DIFF="$(which colordiff)"
+else
+  DIFF="$(which diff)"
+fi
+
+# Make sure the formatter is built in debug mode so we can reference the
+# executable easily.
+swift build --product swift-format
+
+# Run a side-by-side diff with the original source file on the left and the
+# formatted output on the right.
+"$DIFF" -y -W 210 "$SRCFILE" <(.build/debug/swift-format -p "$@" "$SRCFILE")