Completions

bake-completion.sh

@@ -1,13 +1,30 @@
 #!/usr/bin/env bash
 
+BAKE_COMPLETIONS="${BAKE_COMPLETIONS:-Bakefile.completions}"
+
 _bake () {
-  local cword cur tasks
-  _get_comp_words_by_ref -n : -c cur cword
+  local cword cur tasks words
+  _get_comp_words_by_ref -n : -c cur cword words
   tasks="$(bake | grep -v BAKEFILE | grep '^  ' | sed 's/^  //g' | cut -f1 -d' ')"
   if [[ "$cword" -eq "1" ]]; then
     mapfile -t COMPREPLY < <(compgen -W "$tasks" -- "$cur")
   else
-    mapfile -t COMPREPLY < <(compgen -o default -- "$cur")
+    if [ -f "$BAKE_COMPLETIONS" ]; then
+      # shellcheck disable=SC1090
+      source "$BAKE_COMPLETIONS"
+    else
+      mapfile -t COMPREPLY < <(compgen -o default -- "$cur")
+      return 0
+    fi
+
+    local completion_fn="_bake_completions_${words[1]}" # task name
+    if declare -F "$completion_fn" &>/dev/null; then
+      # complete using provided completer
+      mapfile -t COMPREPLY < <("$completion_fn" "$cur")
+    else
+      # fallback on default completer
+      mapfile -t COMPREPLY < <(compgen -o default -- "$cur")
+    fi
   fi
 
   # NB: this is a workaround for bash's default of splitting words on colons

sandbox/Bakefile

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+
+bake_task docker
+function docker () {
+  command docker "$@"
+}

sandbox/Bakefile.completions

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+
+function _bake_completions_docker () {
+  local cur words docker_cmd
+  _get_comp_words_by_ref -n : -c cur words
+  docker_cmd=( "${words[@]:1}" )
+  compgen -W "$(get_completions "${docker_cmd[@]}")" -- "$cur"
+}

sandbox/get_completions.sh

@@ -0,0 +1,50 @@
+#
+# Author: Brian Beffa <brbsix@gmail.com>
+# Original source: https://brbsix.github.io/2015/11/29/accessing-tab-completion-programmatically-in-bash/
+# License: LGPLv3 (http://www.gnu.org/licenses/lgpl-3.0.txt)
+#
+
+get_completions(){
+    local completion COMP_CWORD COMP_LINE COMP_POINT COMP_WORDS COMPREPLY=()
+
+    # load bash-completion if necessary
+    declare -F _completion_loader &>/dev/null || {
+        source /usr/share/bash-completion/bash_completion
+    }
+
+    COMP_LINE=$*
+    COMP_POINT=${#COMP_LINE}
+
+    eval set -- "$@"
+
+    COMP_WORDS=("$@")
+
+    # add '' to COMP_WORDS if the last character of the command line is a space
+    [[ ${COMP_LINE[*]: -1} = ' ' ]] && COMP_WORDS+=('')
+
+    # index of the last word
+    COMP_CWORD=$(( ${#COMP_WORDS[@]} - 1 ))
+
+    # determine completion function
+    completion=$(complete -p "$1" 2>/dev/null | awk '{print $(NF-1)}')
+
+    # run _completion_loader only if necessary
+    [[ -n $completion ]] || {
+
+        # load completion
+        _completion_loader "$1"
+
+        # detect completion
+        completion=$(complete -p "$1" 2>/dev/null | awk '{print $(NF-1)}')
+
+    }
+
+    # ensure completion was detected
+    [[ -n $completion ]] || return 1
+
+    # execute completion function
+    "$completion"
+
+    # print completions to stdout
+    printf '%s\n' "${COMPREPLY[@]}" | LC_ALL=C sort
+}