Model what each parser does with an empty and a dangling directive

Review of the previous commits turned up four places where the predicates
and their tests disagreed with the tools they are modelling, each checked
against udevadm verify, systemd-analyze verify and visudo -cf rather than
against reading of the sources.

An empty ExecStop= resets the list, so a unit an administrator neutralised
that way runs nothing at shutdown and is no longer ours to remove; the
predicate now tracks the last state instead of returning on the first home
path it sees. A file whose last line ends in a backslash still carries a
live directive for systemd, so the pending logical line is emitted at EOF;
udev ignores such a line and sudo rejects the file outright, so this costs
those two nothing. The scanner's taint pass now reads += appends, which its
own comment already promised: the value of an append is no use, but a name
that reaches a user root through one has to be judged on it.

Two regression guards passed against the implementations they were written
for. The udev continuation fixture put the whole RUN+= below the comment, so
it matched whether or not the pending half was carried across; the split now
falls inside the RUN+= value. The sudoers one kept its file on the strength
of a spec above the comment, so it could not fail either; the hand-written
spec now sits below. Both fail against a mutant that discards the pending
line. The comment above the second also claimed a continued comment stays a
comment, which visudo contradicts.

migrations/1788025225.sh

@@ -67,6 +67,12 @@ active_lines() {
     emit_logical "$logical$line"
     logical=""
   done
+
+  # A file whose last line ends in a backslash still carries a live directive for
+  # systemd: `systemd-analyze verify` resolves an ExecStop= written that way.
+  # udev ignores the dangling line and sudo rejects the file outright, so emitting
+  # it costs those two nothing.
+  emit_logical "$logical"
 }
 
 # One logical line, whitespace collapsed so a reformatted copy still compares
@@ -195,6 +201,7 @@ plymouth_unit_runs_from_home() {
   local home_pattern="^(/home/[^/]+|/root)/\\.local/share/omarchy/bin/$binary\$"
   local line word
   local -a words
+  local matched=1
 
   while IFS= read -r line; do
     if [[ ! $line =~ $exec_stop_pattern ]]; then
@@ -203,6 +210,11 @@ plymouth_unit_runs_from_home() {
 
     read -ra words <<<"${BASH_REMATCH[1]}"
     if (( ! ${#words[@]} )); then
+      # An empty assignment resets the list, so nothing named before it still
+      # runs. `systemd-analyze verify` reports the missing command for a unit
+      # with one ExecStop=, and reports nothing once a bare ExecStop= follows it.
+      # An administrator who neutralised the unit this way is left alone.
+      matched=1
       continue
     fi
 
@@ -214,11 +226,13 @@ plymouth_unit_runs_from_home() {
     done
 
     if [[ $word =~ $home_pattern || $word == "$HOME/.local/share/omarchy/bin/$binary" ]]; then
-      return 0
+      matched=0
+    else
+      matched=1
     fi
   done < <(active_lines systemd)
 
-  return 1
+  return $matched
 }
 
 # /etc/sudoers.d is 0750 root:root as shipped, and omarchy-migrate runs as the

test/shell.d/legacy-power-udev-rules-migration-test.sh

@@ -213,14 +213,16 @@ run_migration
   fail "migration matches the binary the filename promises, not any home path"
 pass "migration matches the binary the filename promises, not any home path"
 
-# udev resumes a continuation across a comment: `udevadm verify` on
+# udev resumes a continuation across a comment: `udevadm verify` reports its
-# 'SUBSYSTEM=="power_supply" \' + "# c" + ', RUN+="..."' reports its style warning
+# complaint on line 1 for a rule split this way, so the three lines are one live
-# on line 1, so those three lines are one rule and the rule is live.
+# rule. The split falls inside the RUN+= value on purpose -- with the whole
+# RUN+= below the comment the assertion passes even against an implementation
+# that throws the pending half away, which is the shape this guards against.
 reset_machine
 cat >"$power_rule" <<'RULE'
-SUBSYSTEM=="power_supply", ATTR{type}=="Mains" \
+SUBSYSTEM=="power_supply", ATTR{type}=="Mains", RUN+="/usr/bin/systemd-run --no-block --unit=omarchy-power-profile \
 # split for readability
-, RUN+="/home/someuser/.local/share/omarchy/bin/omarchy-powerprofiles-set"
+/home/someuser/.local/share/omarchy/bin/omarchy-powerprofiles-set"
 RULE
 run_migration
 

test/shell.d/privileged-heredoc-test.sh

@@ -176,16 +176,17 @@ declare -A VARS_TAINTED=()
 # isolation would miss in whichever direction it picked.
 collect_vars() {
   local -n source_lines="$1"
-  local line name value
+  local line name value append
 
   VARS=()
   VARS_TAINTED=()
   for line in "${source_lines[@]}"; do
     [[ $line =~ ^[[:space:]]*# ]] && continue
-    [[ $line =~ ^[[:space:]]*(local|declare|export|readonly|typeset)?[[:space:]]*([A-Za-z_][A-Za-z0-9_]*)=(.*)$ ]] || continue
+    [[ $line =~ ^[[:space:]]*(local|declare|export|readonly|typeset)?[[:space:]]*([A-Za-z_][A-Za-z0-9_]*)(\+?)=(.*)$ ]] || continue
 
     name=${BASH_REMATCH[2]}
-    value=${BASH_REMATCH[3]}
+    append=${BASH_REMATCH[3]}
+    value=${BASH_REMATCH[4]}
     value=${value%%[[:space:]]#*}
     value=${value%[[:space:]]}
     if [[ $value == \"*\" || $value == \'*\' ]]; then
@@ -193,6 +194,11 @@ collect_vars() {
     fi
 
     mentions_user_writable_root "$value" && VARS_TAINTED["$name"]=1
+
+    # An append never wins the value -- an array grown across a file resolves to
+    # nothing useful -- but it does carry the taint, or a name could reach a user
+    # root through += and never be judged on it.
+    [[ -n $append ]] && continue
     [[ -v VARS[$name] ]] || VARS["$name"]=$value
   done
 }
@@ -457,9 +463,8 @@ privileged_destination() {
     fi
   done < <(command_destinations "$line")
 
-  # An elevated write whose destination cannot be resolved counts as
+  # An elevated write whose destination cannot be resolved counts as privileged:
-  # privileged: sudo tee is not aimed at a user's own dotfile, and assuming
+  # sudo tee is not aimed at a user's own dotfile.
-  # otherwise is how this bug class survived six reviews.
   if ((elevated == 0)) && ((${#unresolved[@]} > 0)); then
     printf '%s' "${unresolved[0]} (unresolved destination of an elevated write)"
     return 0

test/shell.d/retired-installer-artifacts-migration-test.sh

@@ -197,21 +197,25 @@ run_migration
   fail "migration keeps a same-named file that never cleaned itself up"
 pass "migration keeps a same-named file that never cleaned itself up"
 
-# A rule continued onto the next line is one logical line, and a comment that is
+# A spec continued onto the next line is one logical line, and a comment's own
-# continued stays a comment for the whole of it.
+# trailing backslash swallows nothing: `visudo -cf` on "# note \" plus a bogus
+# token reports the error on line 2, so the spec below a commented line is live.
+# The hand-written spec sits under the comment on purpose -- above it, the file
+# is kept under either reading and the assertion cannot fail.
 reset_machine
 cat >"$first_run" <<'EOF'
 # Retired, keeping the old grant here for reference: \
-installer ALL=(ALL) NOPASSWD: /usr/bin/systemctl
+installer ALL=(ALL) NOPASSWD: /usr/local/bin/our-own-deploy-script
 Cmnd_Alias FIRST_RUN_CLEANUP = /bin/rm -f /etc/sudoers.d/first-run
 installer ALL=(ALL) NOPASSWD: \
-    /usr/local/bin/our-own-deploy-script
+    /usr/bin/systemctl
+installer ALL=(ALL) NOPASSWD: FIRST_RUN_CLEANUP
 EOF
 run_migration
 
 [[ -e $first_run ]] ||
-  fail "migration reads a continued line as one rule and a continued comment as comment"
+  fail "migration keeps a spec left live under a commented continuation"
-pass "migration reads a continued line as one rule and a continued comment as comment"
+pass "migration keeps a spec left live under a commented continuation"
 
 reset_machine
 printf 'installer ALL=(ALL) NOPASSWD: %s/.local/bin/tsui\n' "$home_dir" >"$tsui"
@@ -454,3 +458,49 @@ run_migration
 [[ ! -e $plymouth_unit ]] ||
   fail "migration removes a unit whose ExecStop continues across a comment" "$(cat "$plymouth_unit")"
 pass "migration removes a unit whose ExecStop continues across a comment"
+
+# An empty ExecStop= resets the list: `systemd-analyze verify` reports the missing
+# command for a unit with one ExecStop=, and reports nothing once a bare
+# ExecStop= follows it. An administrator who neutralised the unit that way runs
+# nothing at shutdown and keeps their file.
+reset_machine
+cat >"$plymouth_unit" <<'EOF'
+[Service]
+Type=oneshot
+ExecStart=/usr/bin/true
+ExecStop=/home/installer/.local/share/omarchy/bin/omarchy-plymouth-shutdown-sync
+ExecStop=
+EOF
+before=$(cat "$plymouth_unit")
+run_migration
+
+[[ -e $plymouth_unit ]] ||
+  fail "migration keeps a unit whose ExecStop list was reset to empty"
+[[ $(cat "$plymouth_unit") == "$before" ]] ||
+  fail "migration leaves that unit byte for byte"
+pass "migration keeps a unit whose ExecStop list was reset to empty"
+
+# A reset followed by a fresh home ExecStop= is live again.
+reset_machine
+cat >"$plymouth_unit" <<'EOF'
+[Service]
+Type=oneshot
+ExecStart=/usr/bin/true
+ExecStop=
+ExecStop=/home/installer/.local/share/omarchy/bin/omarchy-plymouth-shutdown-sync
+EOF
+run_migration
+
+[[ ! -e $plymouth_unit ]] ||
+  fail "migration removes a unit whose ExecStop is set again after a reset"
+pass "migration removes a unit whose ExecStop is set again after a reset"
+
+# systemd honours a directive whose line ends the file mid-continuation:
+# `systemd-analyze verify` resolves an ExecStop= written that way.
+reset_machine
+printf '[Service]\nType=oneshot\nExecStart=/usr/bin/true\nExecStop=/home/installer/.local/share/omarchy/bin/omarchy-plymouth-shutdown-sync \\\n' >"$plymouth_unit"
+run_migration
+
+[[ ! -e $plymouth_unit ]] ||
+  fail "migration removes a unit whose last line ends mid-continuation"
+pass "migration removes a unit whose last line ends mid-continuation"