fix(shell/cached-eval): find usable md5 command and improve reliability

zshenv

@@ -85,8 +85,7 @@ source-if-exists() {
 #   $1 - source_file: The path to the source file that the command depends on.
 #                     If this file is newer than the cache, the command is
 #                     re-executed and the cache is updated.
-#   $2 - cmd:         The command to execute.
-#   $@ - args:        Additional arguments to pass to the command.
+#   $@ - script:      The command to execute and cache the output of.
 #
 # Example usage:
 #
@@ -98,25 +97,30 @@ source-if-exists() {
 # command is re-executed and cache is updated.
 cached-eval() {
   local source_file="$1"
-  local cmd="$2"
-  shift 2
-  local args="$@"
-  local full_cmd="$cmd $args"
+  shift 1
+  local script="$@"
+
   local cache_dir="${ZSH_CACHED_EVAL_DIR:-$HOME/.local/share/zsh/cached-eval}"
 
-  if [[ -z "$(command -v "$cmd")" ]]; then
-    echo "cached-eval: Command not found: $cmd" >&2
+  if [[ ! -f "$source_file" ]]; then
+    echo "cached-eval: Source file not found: $source_file" >&2
     return 1
   fi
 
-  local cache_hash="$(echo -n "$full_cmd" | md5sum | awk '{print $1}')"
-  local cache_file="${cache_dir}/$(basename "$cmd")_${cache_hash}.zsh"
+  local md5_cmd="$(command -v md5 || command -v md5sum)"
+  local cache_hash="$(echo -n "$script" | "$md5_cmd" | awk '{print $1}')"
+  local cache_file="${cache_dir}/${cache_hash}.cache.zsh"
+
+  if [ -z "$cache_hash" ]; then
+    echo "cached-eval: Failed to compute cache hash for: $script" >&2
+    return 1
+  fi
 
   if [[ ! -f "$cache_file" || "$source_file" -nt "$cache_file" ]]; then
     mkdir -p "$cache_dir"
-    echo "cached-eval: Updating cache for: $full_cmd --> $cache_file" >&2
-    echo -e "#\n# Generated by cached-eval: $full_cmd\n#\n" >| "$cache_file"
-    eval "$full_cmd" >>| "$cache_file"
+    echo "cached-eval: Updating cache for: $script --> $cache_file" >&2
+    echo -e "#\n# Generated by cached-eval: $script\n#\n" >| "$cache_file"
+    eval "$script" >>| "$cache_file"
   fi
 
   source "$cache_file"
@@ -178,7 +182,7 @@ fi
 
 # Homebrew on Apple Silicon
 if [ -f "/opt/homebrew/bin/brew" ]; then
-  cached-eval /opt/homebrew/bin/brew /opt/homebrew/bin/brew shellenv
+  cached-eval "/opt/homebrew/bin/brew" /opt/homebrew/bin/brew shellenv
 fi
 
 if command-exists brew; then