harden the config reader against an empty or malformed .env

holcommon's empty .env made the loader evaluate one blank line, which
tripped set -u. Verified afterwards on holcommon's real host stack: the CLI
and the make engine resolve the same five files and render a byte-identical
241-line compose config.

bin/myos

@@ -118,7 +118,7 @@ WORKDIR=${WORKDIR:-$PWD}
 WORKDIR=$(cd "$WORKDIR" 2>/dev/null && pwd -P) || myos_die "$MYOS_E_USAGE" "no such directory: $WORKDIR"
 
 for _f in $(myos_conf_files); do myos_dotenv_load "$_f"; done
-myos_dotenv_load "$HOME/.config/myos/config"
+myos_dotenv_load "${HOME:-}/.config/myos/config"
 ENV=${ENV:-local}
 myos_dotenv_load "$WORKDIR/.env.$ENV"
 myos_dotenv_load "$WORKDIR/.env"

lib/cmd/doctor.sh

@@ -18,7 +18,7 @@ myos_cmd_doctor() {
 
   printf 'configuration:\n'
   for _f in $(myos_conf_files); do _ok "$_f" "read"; done
-  [ -f "$HOME/.config/myos/config" ] && _ok "$HOME/.config/myos/config" "read"
+  [ -f "${HOME:-}/.config/myos/config" ] && _ok "${HOME:-}/.config/myos/config" "read"
   [ -f "$WORKDIR/.env" ] && _ok "$WORKDIR/.env" "read"
   _ok ENV "$ENV"
   _ok USER "$USER"

lib/config.sh

@@ -36,7 +36,10 @@ myos_dotenv_parse() {
 myos_dotenv_load() {
   [ -f "$1" ] || return 0
   while IFS= read -r _kv; do
+    # an empty file still yields one empty line through the here-document
+    [ -n "$_kv" ] || continue
     _k=${_kv%%=*}
+    [ -n "$_k" ] || continue
     [ -n "$(myos_var "$_k")" ] && continue
     eval "$_k=\${_kv#*=}"
   done <<EOF

lib/stack.sh

@@ -15,7 +15,7 @@ myos_path() {
   _wd=${WORKDIR:-$PWD}
   _name=${STACK_DIR_NAME:-stack}
   _out=
-  for _d in "$_wd" "$_wd/.." "$HOME/.local/share" /usr/local/share /usr/share; do
+  for _d in "$_wd" "$_wd/.." "${HOME:-/nonexistent}/.local/share" /usr/local/share /usr/share; do
     for _c in "$_d/$_name" "$_d/myos/$_name"; do
       [ -d "$_c" ] || continue
       _c=$(cd "$_c" && pwd -P)

lib/tags.sh

@@ -6,7 +6,10 @@
 # to consul, fabio routes on the urlprefix- tags it finds there.
 
 # myos_var NAME  value of the variable named NAME, empty when unset
-myos_var() { eval "printf '%s' \"\${$1:-}\""; }
+myos_var() {
+  [ -n "${1:-}" ] || return 0
+  eval "printf '%s' \"\${$1:-}\""
+}
 
 # myos_uri SERVICE PORT [BASE_URI]
 # <service>.<base uri>, unless <SERVICE>_SERVICE[_<port>]_NAME overrides the prefix

spec/unit/config_spec.sh

@@ -80,3 +80,27 @@ Describe 'lib/config.sh'
     End
   End
 End
+
+Describe 'lib/config.sh robustness'
+  setup() { MYOS_TMP=$(mktemp -d "${TMPDIR:-/tmp}/myos-cfg.XXXXXX"); }
+  cleanup() { rm -rf "$MYOS_TMP"; }
+  BeforeEach setup
+  AfterEach cleanup
+
+  It 'loads an empty .env without complaining'
+    : > "$MYOS_TMP/.env"
+    When call myos_dotenv_load "$MYOS_TMP/.env"
+    The status should be success
+    The stderr should equal ""
+  End
+  It 'ignores a line with an empty key'
+    printf '=orphan\nGOOD=1\n' > "$MYOS_TMP/.env"
+    When call myos_dotenv_parse "$MYOS_TMP/.env"
+    The output should equal "GOOD=1"
+  End
+  It 'returns empty for an unnamed variable'
+    When call myos_var ""
+    The output should equal ""
+    The status should be success
+  End
+End