refactor(build): Streamline and modernize Emacs build script

The script has been redesigned with clearer organization, better
error handling, and more intelligent defaults. Key improvements
include auto-detection for Wayland, better parallel build support,
and more robust git operations.

1 files changed, 75 insertions, 105 deletions

diff --git a/scripts/build-emacs.sh b/scripts/build-emacs.sh
index c5c92b96..5ac2d705 100755
--- a/scripts/build-emacs.sh
+++ b/scripts/build-emacs.sh
@@ -1,119 +1,103 @@
 #!/usr/bin/env bash
 # Craig Jennings <c@cjennings.net>
 # Build & install Emacs from source
-# safe, versioned, user-local, blunt, fast, reversible.
+# safe, user-local, fast, versioned.
 
-set -euo pipefail
+set -Eeuo pipefail
+IFS=$'\n\t'
 
-### --------- CONFIG (edit these) ---------
-# Where the git checkout lives:
+# ---------- Config (override via env) ----------
 SRC_DIR="${SRC_DIR:-$HOME/code/emacs-src}"
-
-# Which repo/branch/tag to build:
 EMACS_REPO="${EMACS_REPO:-https://git.savannah.gnu.org/git/emacs.git}"
-CHECKOUT_REF="${CHECKOUT_REF:-emacs-29.2}"   # e.g. "emacs-30.1", "master", "emacs-29"
-
-# Install prefix (keeps versions side-by-side):
-PREFIX_BASE="${PREFIX_BASE:-$HOME/.local/opt}"
+CHECKOUT_REF="${CHECKOUT_REF:-emacs-30.2}"
+PREFIX_BASE="${PREFIX_BASE:-$HOME/.local/src/emacs}"
 PREFIX="${PREFIX:-$PREFIX_BASE/${CHECKOUT_REF}}"
-
-# Optional knobs:
-ENABLE_NATIVE="${ENABLE_NATIVE:-0}"      # 1 to enable native-comp if toolchain supports it
-ENABLE_PGTK="${ENABLE_PGTK:-0}"          # 1 to use pgtk (Wayland-only build)
-ENABLE_XWIDGETS="${ENABLE_XWIDGETS:-0}"  # 1 to enable xwidgets (known flaky on some 29/30 tags)
-MAKE_JOBS="${MAKE_JOBS:-$(command -v nproc >/dev/null 2>&1 && nproc || sysctl -n hw.ncpu || echo 4)}"
-
-# CFLAGS (tune lightly; keep reproducible):
-CFLAGS_OVERRIDES="${CFLAGS_OVERRIDES:--O2 -march=native}"
-
-LOG_DIR="${LOG_DIR:-$HOME/.cache/build-logs}"
-mkdir -p "$LOG_DIR"
-LOGFILE="$LOG_DIR/emacs-build-$(date +%Y%m%d-%H%M%S)-${CHECKOUT_REF}.log"
-### ---------------------------------------
-
-say() { printf '%s\n' "$*" | tee -a "$LOGFILE" ; }
+LOG_DIR="${LOG_DIR:-$HOME/.cache/emacs-build-logs}"
+ENABLE_NATIVE="${ENABLE_NATIVE:-1}"
+WITH_PGTK="${WITH_PGTK:-auto}"
+JOBS="${JOBS:-auto}"
+EXTRA_CONFIG="${EXTRA_CONFIG:-}"
+
+# ---------- Preflight ----------
+umask 022
+mkdir -p "$LOG_DIR" "$PREFIX_BASE" "$HOME/.local/bin"
+: "${LOGFILE:=$LOG_DIR/emacs-build-$(date +%Y%m%d-%H%M%S)-${CHECKOUT_REF}.log}"
+
+say() { printf '>>> %s\n' "$*" | tee -a "$LOGFILE" ; }
 run() { say "+ $*"; eval "$@" >>"$LOGFILE" 2>&1; }
+on_err(){ ec=$?; echo "ERROR [$ec] - see $LOGFILE" >&2; tail -n 80 "$LOGFILE" >&2 || true; exit "$ec"; }
+trap on_err ERR
 
-trap 'echo "ERROR: see $LOGFILE" >&2' ERR
-
-say ">>> Building Emacs"
-say "SRC_DIR=$SRC_DIR"
-say "CHECKOUT_REF=$CHECKOUT_REF"
-say "PREFIX=$PREFIX"
-say "LOGFILE=$LOGFILE"
-
-# Fetch or update source
+# ---------- Clone/update ----------
 if [[ -d "$SRC_DIR/.git" ]]; then
-  say "...updating existing checkout"
-  (cd "$SRC_DIR" && run "git fetch --tags --prune" && run "git status --porcelain")
+  run "git -C '$SRC_DIR' fetch --tags --prune"
 else
-  say "...cloning source"
   mkdir -p "$(dirname "$SRC_DIR")"
-  run "git clone --depth=1 --branch ${CHECKOUT_REF} ${EMACS_REPO} ${SRC_DIR}" || {
-    # If ref isn’t a branch, do full clone then checkout tag
-    run "git clone ${EMACS_REPO} ${SRC_DIR}"
-  }
+  run "git clone --origin origin '$EMACS_REPO' '$SRC_DIR'"
 fi
 
-# Checkout desired ref/tag
-(
-  cd "$SRC_DIR"
-  run "git fetch --tags --force"
-  run "git checkout ${CHECKOUT_REF}"
-)
+run "git -C '$SRC_DIR' reset --hard HEAD"
+run "git -C '$SRC_DIR' clean -fdx"
+run "git -C '$SRC_DIR' checkout -f '$CHECKOUT_REF'"
+run "git -C '$SRC_DIR' submodule update --init --recursive || true"
 
-# Autogen/bootstrap (needed for git checkouts)
+# ---------- Autogen ----------
 if [[ -x "$SRC_DIR/autogen.sh" ]]; then
-  say "...running autogen.sh"
-  (cd "$SRC_DIR" && run "./autogen.sh")
+  run "cd '$SRC_DIR' && ./autogen.sh"
 fi
 
-# Configure flags
+# ---------- Configure flags (ARRAY!) ----------
 conf_flags=(
   "--prefix=${PREFIX}"
   "--with-json"
   "--with-modules"
-  "--with-cairo"
-  "--with-harfbuzz"
-  "--with-native-compilation=$( [[ $ENABLE_NATIVE -eq 1 ]] && echo yes || echo no )"
-  "--with-mailutils"
-  "--with-imagemagick"
 )
 
-# pgtk vs X
-if [[ $ENABLE_PGTK -eq 1 ]]; then
-  conf_flags+=("--with-pgtk" "--without-x")
+# Wayland/X choice
+if [[ "$WITH_PGTK" == "auto" ]]; then
+  if [[ -n "${WAYLAND_DISPLAY:-}" ]]; then WITH_PGTK="yes"; else WITH_PGTK="no"; fi
+fi
+if [[ "$WITH_PGTK" == "yes" ]]; then
+  conf_flags+=("--with-pgtk")
 else
-  conf_flags+=("--with-x" "--with-x-toolkit=gtk3")
+  conf_flags+=("--with-x-toolkit=lucid")
 fi
 
-# xwidgets if requested
-if [[ $ENABLE_XWIDGETS -eq 1 ]]; then
-  conf_flags+=("--with-xwidgets")
+# Native-compilation
+if [[ "$ENABLE_NATIVE" == "1" ]]; then
+  conf_flags+=("--with-native-compilation=yes")
+else
+  conf_flags+=("--with-native-compilation=no")
 fi
 
-# Prefer system tree-sitter if present
-if pkg-config --exists tree-sitter 2>/dev/null; then
-  conf_flags+=("--with-tree-sitter")
+# Useful extras (disable later via EXTRA_CONFIG if missing deps)
+conf_flags+=(
+  "--with-cairo"
+  "--with-harfbuzz"
+  "--with-tree-sitter"
+  "--with-imagemagick"
+  "--with-mailutils"
+)
+
+# Optional extra flags from env
+if [[ -n "$EXTRA_CONFIG" ]]; then
+  # shellcheck disable=SC2206
+  conf_flags+=($EXTRA_CONFIG)
 fi
 
-say "...configure flags:"
-printf '   %s\n' "${conf_flags[@]}" | tee -a "$LOGFILE"
+# ---------- Build & install ----------
+mkdir -p "$PREFIX"
 
-# Configure
-mkdir -p "$PREFIX"  # ensure we can write there
-(
-  cd "$SRC_DIR"
-  run "env CFLAGS='${CFLAGS_OVERRIDES}' ./configure ${conf_flags[*]}"
-)
+# Temporarily change IFS to space for configure argument expansion
+old_ifs="$IFS"
+IFS=' '
+run "cd '$SRC_DIR' && ./configure ${conf_flags[*]}"
+IFS="$old_ifs"
 
-# Build (and bootstrap if needed)
-say "...compiling (jobs=$MAKE_JOBS)"
-(
-  cd "$SRC_DIR"
-  # master sometimes needs bootstrap after significant changes; harmless otherwise:
-  run "make -j${MAKE_JOBS}"
-)
+if [[ "$JOBS" == "auto" ]]; then
+  if command -v nproc >/dev/null 2>&1; then JOBS=$(nproc); else JOBS=4; fi
+fi
+run "cd '$SRC_DIR' && make -j$JOBS"
 
 # Build documentation (info files)
 say "...building info files"
@@ -122,33 +106,19 @@ say "...building info files"
   run "make info"
 )
 
-# Install to user-local prefix
-say "...installing to ${PREFIX}"
-(
-  cd "$SRC_DIR"
-  run "make install"
-  run "make install-info"
-)
+run "cd '$SRC_DIR' && make install"
+run "cd '$SRC_DIR' && make install-info"
 
-# ymlink all installed executables (emacs, emacsclient, etags, etc.)
-mkdir -p "$HOME/.local/bin"
-
-# Atomic swap: build symlinks in a temp dir, then move them into place.
+# ---------- Symlinks ----------
+run "ln -sfn '$PREFIX' '$PREFIX_BASE/emacs-current'"
 tmpdir="$(mktemp -d)"
-for exe in "$PREFIX/bin/"*; do
-  [ -x "$exe" ] || continue
-  name="$(basename "$exe")"
-  ln -s "$exe" "$tmpdir/$name"
-done
-
-# Move into ~/.local/bin (overwriting existing symlinks/files with same names)
-for link in "$tmpdir"/*; do
-  name="$(basename "$link")"
-  mv -f "$link" "$HOME/.local/bin/$name"
+for exe in "$PREFIX/bin/emacs" "$PREFIX/bin/emacsclient"; do
+  [[ -x "$exe" ]] || continue
+  ln -s "$exe" "$tmpdir/$(basename "$exe")"
 done
+mv -f "$tmpdir"/* "$HOME/.local/bin/" || { echo "Failed to install shims to ~/.local/bin" >&2; exit 72; }
 rmdir "$tmpdir"
 
-# Optional: quick sanity print
 command -v emacs >/dev/null && emacs --version | head -n1 || true
 command -v emacsclient >/dev/null && emacsclient --version | head -n1 || true
-
+echo "Done. See $LOGFILE"