utils/shfmt.sh: add function prototypes

Library/Homebrew/utils/shfmt.sh

@@ -1,12 +1,19 @@
 #!/bin/bash
 
-# HOMEBREW_LIBRARY is set by bin/brew
+onoe() {
+  echo "$*" >&2
+}
+
+odie() {
+  onoe "$@"
+  exit 1
+}
+
 # HOMEBREW_PREFIX is set by extend/ENV/super.rb
 # shellcheck disable=SC2154
-if [[ -z "${HOMEBREW_LIBRARY}" || -z "${HOMEBREW_PREFIX}" ]]
+if [[ -z "${HOMEBREW_PREFIX}" ]]
 then
-  echo "${0##*/}: This program is internal and must be run via brew." >&2
-  exit 1
+  odie "${0##*/}: This program is internal and must be run via brew."
 fi
 
 # HOMEBREW_PREFIX is set by extend/ENV/super.rb
@@ -15,8 +22,12 @@ SHFMT="${HOMEBREW_PREFIX}/opt/shfmt/bin/shfmt"
 
 if [[ ! -x "${SHFMT}" ]]
 then
-  echo "${0##*/}: Please install shfmt by running \`brew install shfmt\`." >&2
-  exit 1
+  odie "${0##*/}: Please install shfmt by running \`brew install shfmt\`."
+fi
+
+if [[ ! -x "$(command -v diff)" ]]
+then
+  odie "${0##*/}: Please install diff by running \`brew install diffutils\`."
 fi
 
 SHFMT_ARGS=()
@@ -56,4 +67,175 @@ then
   exit
 fi
 
-"${SHFMT}" "${SHFMT_ARGS[@]}" "${FILES[@]}"
+check_read_and_write() {
+  [[ -f "$1" && -w "$1" ]]
+}
+
+###
+### Custom shell script styling
+###
+
+# Check pattern:
+# '^\t+'
+#
+# Replace tabs with 2 spaces instead
+#
+no_tabs() {
+  local file="$1"
+
+  # TODO: use bash built-in regex match syntax instead
+  if grep -qE '^\t+' "${file}"
+  then
+    # TODO: add line number
+    onoe "Indent by tab detected."
+    return 1
+  fi
+}
+
+# Check pattern:
+# for var in ... \
+#            ...; do
+#
+# Use the followings instead (keep for statements only one line):
+# ARRAY=(
+#   ...
+#   ...
+# )
+# for var in "${ARRAY[@]}"
+# do
+#
+no_multiline_for_statements() {
+  local file="$1"
+  check_read_and_write "${file}" || return 1
+
+  # TODO: use bash built-in regex match syntax instead
+  if grep -qE '^\s*for .*\\\(#.*\)\?$' "${file}"
+  then
+    # TODO: add line number
+    onoe "Multi-line for statement detected."
+    return 1
+  fi
+}
+
+# Check pattern:
+# IFS=$'\n'
+#
+# Use the followings instead:
+# while IFS='' read -r line
+# do
+#   ...
+# done < <(command)
+#
+no_IFS_newline() {
+  local file="$1"
+  check_read_and_write "${file}" || return 1
+
+
+  # TODO: use bash built-in regex match syntax instead
+  if grep -qE "^[^#]*IFS=\\\$'\\\\n'" "${file}"
+  then
+    # TODO: add line number
+    onoe "Pattern \`IFS=\$'\\\\n'\` detected."
+    return 1
+  fi
+}
+
+# TODO: Wrap `then` to a separated line
+# before:                   after:
+# if [[ ... ]]; then        if [[ ... ]]
+#                           then
+#
+# before:                   after:
+# if [[ ... ]] ||           if [[ ... ]] ||
+#   [[ ... ]]; then           [[ ... ]]
+#                           then
+#
+wrap_then() {
+  local file="$1"
+  check_read_and_write "${file}" || return 1
+
+  true
+}
+
+# Probably merge into the above function
+# TODO: Wrap `do` to a separated line
+# before:                   after:
+# for var in ...; do        for var in ...do
+#                           do
+#
+wrap_do() {
+  local file="$1"
+  check_read_and_write "${file}" || return 1
+
+  true
+}
+
+# TODO: Align multiline if condition (indent with 3 spaces or 6 spaces (start with "-"))
+# before:                   after:
+# if [[ ... ]] ||           if [[ ... ]] ||
+#   [[ ... ]]                  [[ ... ]]
+# then                      then
+#
+# before:                   after:
+# if [[ -n ... || \         if [[ -n ... || \
+#   -n ... ]]                     -n ... ]]
+# then                      then
+#
+align_multiline_if_condition() {
+  local file="$1"
+  check_read_and_write "${file}" || return 1
+
+  true
+}
+
+# TODO: It's hard to align multiline switch cases
+align_multiline_switch_cases() {
+  true
+}
+
+format() {
+  local file="$1"
+  # shellcheck disable=SC2155
+  local tempfile="$(dirname "${file}")/.${file##*/}.temp"
+  local retcode=0
+
+  cp -af "${file}" "${tempfile}"
+
+  # Format with `shfmt` first
+  "${SHFMT}" -w "${SHFMT_ARGS[@]}" "${tempfile}"
+
+  # Fail fast when forbidden patterns detected
+  if ! no_tabs "${tempfile}" ||
+     ! no_multiline_for_statements "${tempfile}" ||
+     ! no_IFS_newline "${tempfile}"
+  then
+    rm -f "${tempfile}" 2>/dev/null
+    return 1
+  fi
+
+  # Tweak it with custom shell script styles
+  wrap_then "${tempfile}"
+  wrap_do "${tempfile}"
+  align_multiline_if_condition "${tempfile}"
+
+  if ! diff -q "${file}" "${tempfile}"
+  then
+    # Show differences
+    diff -d -C 1 --color=auto "${file}" "${tempfile}"
+    if [[ -n "${INPLACE}" ]]; then
+      cp -af "${tempfile}" "${file}"
+    fi
+    retcode=1
+  else
+    # File is identical between code formations (good styling)
+    retcode=0
+  fi
+  rm -f "${tempfile}" 2>/dev/null
+  return "${retcode}"
+}
+
+for file in "${FILES[@]}"
+do
+  # TODO: catch return values
+  format "${file}"
+done