style: add shfmt implementation

Library/Homebrew/style.rb

@@ -65,6 +65,8 @@ module Homebrew
         run_shellcheck(shell_files, output_type)
       end
 
+      run_shfmt(shell_files) if ruby_files.none? || shell_files.any?
+
       if output_type == :json
         Offenses.new(rubocop_result + shellcheck_result)
       else
@@ -164,30 +166,7 @@ module Homebrew
     end
 
     def run_shellcheck(files, output_type)
-      # Always use the latest brewed shellcheck
+      files = [*shell_scripts, HOMEBREW_REPOSITORY/"Dockerfile"] if files.empty?
-      unless Formula["shellcheck"].latest_version_installed?
-        if Formula["shellcheck"].any_version_installed?
-          ohai "Upgrading `shellcheck` for shell style checks..."
-          safe_system HOMEBREW_BREW_FILE, "upgrade", "shellcheck"
-        else
-          ohai "Installing `shellcheck` for shell style checks..."
-          safe_system HOMEBREW_BREW_FILE, "install", "shellcheck"
-        end
-      end
-      shellcheck = Formula["shellcheck"].opt_bin/"shellcheck"
-
-      if files.empty?
-        files = [
-          HOMEBREW_BREW_FILE,
-          HOMEBREW_REPOSITORY/"completions/bash/brew",
-          HOMEBREW_REPOSITORY/"Dockerfile",
-          *HOMEBREW_LIBRARY.glob("Homebrew/*.sh"),
-          *HOMEBREW_LIBRARY.glob("Homebrew/shims/**/*").map(&:realpath).uniq
-                           .reject { |path| path.directory? || path.basename.to_s == "cc" },
-          *HOMEBREW_LIBRARY.glob("Homebrew/{dev-,}cmd/*.sh"),
-          *HOMEBREW_LIBRARY.glob("Homebrew/{cask/,}utils/*.sh"),
-        ]
-      end
 
       args = ["--shell=bash", "--enable=all", "--external-sources", "--source-path=#{HOMEBREW_LIBRARY}", "--", *files]
 
@@ -235,6 +214,15 @@ module Homebrew
       end
     end
 
+    def run_shfmt(files)
+      files = shell_scripts if files.empty?
+
+      args = ["-i", "2", "-ci", "-ln", "bash", "--", *files]
+
+      system shfmt, *args
+      $CHILD_STATUS.success?
+    end
+
     def json_result!(result)
       # An exit status of 1 just means violations were found; other numbers mean
       # execution errors.
@@ -244,6 +232,49 @@ module Homebrew
       JSON.parse(result.stdout)
     end
 
+    def shell_scripts
+      [
+        HOMEBREW_BREW_FILE,
+        HOMEBREW_REPOSITORY/"completions/bash/brew",
+        HOMEBREW_REPOSITORY/"Dockerfile",
+        *HOMEBREW_LIBRARY.glob("Homebrew/*.sh"),
+        *HOMEBREW_LIBRARY.glob("Homebrew/shims/**/*").map(&:realpath).uniq
+                         .reject { |path| path.directory? || path.basename.to_s == "cc" },
+        *HOMEBREW_LIBRARY.glob("Homebrew/{dev-,}cmd/*.sh"),
+        *HOMEBREW_LIBRARY.glob("Homebrew/{cask/,}utils/*.sh"),
+      ]
+    end
+
+    def shellcheck
+      # Always use the latest brewed shellcheck
+      unless Formula["shellcheck"].latest_version_installed?
+        if Formula["shellcheck"].any_version_installed?
+          ohai "Upgrading `shellcheck` for shell style checks..."
+          safe_system HOMEBREW_BREW_FILE, "upgrade", "shellcheck"
+        else
+          ohai "Installing `shellcheck` for shell style checks..."
+          safe_system HOMEBREW_BREW_FILE, "install", "shellcheck"
+        end
+      end
+
+      Formula["shellcheck"].opt_bin/"shellcheck"
+    end
+
+    def shfmt
+      # Always use the latest brewed shfmt
+      unless Formula["shfmt"].latest_version_installed?
+        if Formula["shfmt"].any_version_installed?
+          ohai "Upgrading `shfmt` to format shell scripts..."
+          safe_system HOMEBREW_BREW_FILE, "upgrade", "shfmt"
+        else
+          ohai "Installing `shfmt` to format shell scripts..."
+          safe_system HOMEBREW_BREW_FILE, "install", "shfmt"
+        end
+      end
+
+      HOMEBREW_LIBRARY/"Homebrew/utils/shfmt.sh"
+    end
+
     # Collection of style offenses.
     class Offenses
       include Enumerable

Library/Homebrew/utils/shfmt.sh

@@ -0,0 +1,59 @@
+#!/bin/bash
+
+# HOMEBREW_LIBRARY is set by bin/brew
+# HOMEBREW_PREFIX is set by extend/ENV/super.rb
+# shellcheck disable=SC2154
+if [[ -z "${HOMEBREW_LIBRARY}" || -z "${HOMEBREW_PREFIX}" ]]
+then
+  echo "${0##*/}: This program is internal and must be run via brew." >&2
+  exit 1
+fi
+
+# HOMEBREW_PREFIX is set by extend/ENV/super.rb
+# shellcheck disable=SC2154
+SHFMT="${HOMEBREW_PREFIX}/opt/shfmt/bin/shfmt"
+
+if [[ ! -x "${SHFMT}" ]]
+then
+  echo "${0##*/}: Please install shfmt by running \`brew install shfmt\`." >&2
+  exit 1
+fi
+
+SHFMT_ARGS=()
+INPLACE=''
+while [[ $# -gt 0 ]]
+do
+  arg="$1"
+  if [[ "${arg}" == "--" ]]
+  then
+    shift
+    break
+  fi
+  if [[ "${arg}" == "-w" ]]
+  then
+    shift
+    INPLACE=1
+    continue
+  fi
+  SHFMT_ARGS+=("${arg}")
+  shift
+done
+
+FILES=()
+for file in "$@"
+do
+  if [[ -f "${file}" ]]
+  then
+    FILES+=("${file}")
+  else
+    echo "${0##*/}: File \"${file}\" does not exist." >&2
+    exit 1
+  fi
+done
+
+if [[ "${#FILES[@]}" == 0 ]]
+then
+  exit
+fi
+
+"${SHFMT}" "${SHFMT_ARGS[@]}" "${FILES[@]}"