scripts/bash: Add snap_completer.sh script

This commit adds `snap_completer.sh`, which provides improved bash
completions for the LXD snap.

Signed-off-by: Kadin Sayani <[email protected]>

scripts/bash/snap_completer.sh

@@ -0,0 +1,324 @@
+# shellcheck shell=bash
+
+# Derived from: https://github.com/spf13/cobra/blob/main/bash_completionsV2.go
+# Modifications made by Canonical Ltd, 2024
+# Original work is licensed under the Apache License, Version 2.0
+
+# bash completion V2 for lxc
+# This script provides bash completions for the LXD Snap. Snap completions are achieved by a marshalling script in snapd. Completion requests are intercepted and scanned before serialization by complete.sh, sent to etelpmoc.sh for de-serialization and processing, and finally, results are serialized. See https://github.com/canonical/snapd/blob/master/data/completion/bash/etelpmoc.sh and https://github.com/canonical/snapd/blob/master/data/completion/bash/complete.sh for detailed descriptions on the snapd bash completion process.
+
+__lxc_debug()
+{
+    if [[ -n ${BASH_COMP_DEBUG_FILE-} ]]; then
+        echo "$*" >> "${BASH_COMP_DEBUG_FILE}"
+    fi
+}
+
+# This function calls the lxc program to obtain the completion
+# results and the directive.  It fills the 'out' and 'directive' vars.
+__lxc_get_completion_results() {
+    local requestComp lastParam lastChar args
+
+    # Prepare the command to request completions for the program.
+    # Calling ${words[0]} instead of directly lxc allows handling aliases
+    args=("${words[@]:1}")
+    # Request completions from the LXC binary in LXD's Snap.
+    requestComp="/snap/lxd/current/bin/lxc __complete ${args[*]}"
+
+    lastParam=${words[$((${#words[@]}-1))]}
+    lastChar=${lastParam:$((${#lastParam}-1)):1}
+    __lxc_debug "lastParam ${lastParam}, lastChar ${lastChar}"
+
+    if [[ -z ${cur} && ${lastChar} != = ]]; then
+        # If the last parameter is complete (there is a space following it)
+        # We add an extra empty parameter so we can indicate this to the go method.
+        __lxc_debug "Adding extra empty parameter"
+        requestComp="${requestComp} ''"
+    fi
+
+    # When completing a flag with an = (e.g., lxc -n=<TAB>)
+    # bash focuses on the part after the =, so we need to remove
+    # the flag part from $cur
+    if [[ ${cur} == -*=* ]]; then
+        cur="${cur#*=}"
+    fi
+
+    __lxc_debug "Calling ${requestComp}"
+    # Use eval to handle any environment variables and such
+    out=$(eval "${requestComp}" 2>/dev/null)
+
+    # Extract the directive integer at the very end of the output following a colon (:)
+    directive=${out##*:}
+    # Remove the directive
+    out=${out%:*}
+    if [[ ${directive} == "${out}" ]]; then
+        # There is not directive specified
+        directive=0
+    fi
+    __lxc_debug "The completion directive is: ${directive}"
+    __lxc_debug "The completions are: ${out}"
+}
+
+__lxc_process_completion_results() {
+    local shellCompDirectiveError=1
+    local shellCompDirectiveNoSpace=2
+    local shellCompDirectiveNoFileComp=4
+    local shellCompDirectiveFilterFileExt=8
+    local shellCompDirectiveFilterDirs=16
+    local shellCompDirectiveKeepOrder=32
+
+    if (((directive & shellCompDirectiveError) != 0)); then
+        # Error code.  No completion.
+        __lxc_debug "Received error from custom completion go code"
+        return
+    else
+        if (((directive & shellCompDirectiveNoSpace) != 0)); then
+            __lxc_debug "Activating no space"
+            # Since we know the nospace completion option is supported in the LXD Snap environment, we can set it after receiving a no space completion directive from Cobra.
+            compopt -o nospace
+        fi
+        if (((directive & shellCompDirectiveKeepOrder) != 0)); then
+            # no sort isn't supported for bash less than < 4.4
+            if [[ ${BASH_VERSINFO[0]} -lt 4 || ( ${BASH_VERSINFO[0]} -eq 4 && ${BASH_VERSINFO[1]} -lt 4 ) ]]; then
+                __lxc_debug "No sort directive not supported in this version of bash"
+            else
+                __lxc_debug "Activating keep order"
+                compopt -o nosort
+            fi
+        fi
+        if (((directive & shellCompDirectiveNoFileComp) != 0)); then
+            __lxc_debug "Activating no file completion"
+            compopt +o default
+        fi
+    fi
+
+    # Separate activeHelp from normal completions
+    local completions=()
+    local activeHelp=()
+    __lxc_extract_activeHelp
+
+    if (((directive & shellCompDirectiveFilterFileExt) != 0)); then
+        # File extension filtering
+        local fullFilter filter filteringCmd
+
+        # Do not use quotes around the $completions variable or else newline
+        # characters will be kept.
+        for filter in ${completions[*]}; do
+            fullFilter+="$filter|"
+        done
+
+        filteringCmd="_filedir $fullFilter"
+        __lxc_debug "File filtering command: $filteringCmd"
+        $filteringCmd
+    elif (((directive & shellCompDirectiveFilterDirs) != 0)); then
+        # File completion for directories only
+
+        local subdir
+        subdir=${completions[0]}
+        if [[ -n $subdir ]]; then
+            __lxc_debug "Listing directories in $subdir"
+            pushd "$subdir" >/dev/null 2>&1 && _filedir -d && popd >/dev/null 2>&1 || return
+        else
+            __lxc_debug "Listing directories in ."
+            _filedir -d
+        fi
+    else
+        __lxc_handle_completion_types
+    fi
+
+    __lxc_handle_special_char "$cur" :
+    __lxc_handle_special_char "$cur" =
+
+    # Print the activeHelp statements before we finish
+    if ((${#activeHelp[*]} != 0)); then
+        printf "\n";
+        printf "%s\n" "${activeHelp[@]}"
+        printf "\n"
+
+        # The prompt format is only available from bash 4.4.
+        # We test if it is available before using it.
+        if (x=${PS1@P}) 2> /dev/null; then
+            printf "%s%s" "${PS1@P}" "${COMP_LINE[@]}"
+        else
+            # Can't print the prompt.  Just print the
+            # text the user had typed, it is workable enough.
+            printf "%s" "${COMP_LINE[@]}"
+        fi
+    fi
+}
+
+# Separate activeHelp lines from real completions.
+# Fills the $activeHelp and $completions arrays.
+__lxc_extract_activeHelp() {
+    local activeHelpMarker="_activeHelp_ "
+    local endIndex=${#activeHelpMarker}
+
+    while IFS='' read -r comp; do
+        if [[ ${comp:0:endIndex} == "$activeHelpMarker" ]]; then
+            comp=${comp:endIndex}
+            __lxc_debug "ActiveHelp found: $comp"
+            if [[ -n $comp ]]; then
+                activeHelp+=("$comp")
+            fi
+        else
+            # Not an activeHelp line but a normal completion
+            completions+=("$comp")
+        fi
+    done <<<"${out}"
+}
+
+__lxc_handle_completion_types() {
+    __lxc_debug "__lxc_handle_completion_types: COMP_TYPE is $COMP_TYPE"
+
+    case $COMP_TYPE in
+    37|42)
+        # Type: menu-complete/menu-complete-backward and insert-completions
+        # If the user requested inserting one completion at a time, or all
+        # completions at once on the command-line we must remove the descriptions.
+        # https://github.com/spf13/cobra/issues/1508
+        local tab=$'\t' comp
+        while IFS='' read -r comp; do
+            [[ -z $comp ]] && continue
+            # Strip any description
+            comp=${comp%%$tab*}
+            # Only consider the completions that match
+            if [[ $comp == "$cur"* ]]; then
+                COMPREPLY+=("$comp")
+            fi
+        done < <(printf "%s\n" "${completions[@]}")
+        ;;
+
+    *)
+        # Type: complete (normal completion)
+        __lxc_handle_standard_completion_case
+        ;;
+    esac
+}
+
+__lxc_handle_standard_completion_case() {
+    local tab=$'\t' comp
+
+    # Short circuit to optimize if we don't have descriptions
+    if [[ "${completions[*]}" != *$tab* ]]; then
+        IFS=$'\n' read -ra COMPREPLY -d '' < <(compgen -W "${completions[*]}" -- "$cur")
+        return 0
+    fi
+
+    local longest=0
+    local compline
+    # Look for the longest completion so that we can format things nicely
+    while IFS='' read -r compline; do
+        [[ -z $compline ]] && continue
+        # Strip any description before checking the length
+        comp=${compline%%$tab*}
+        # Only consider the completions that match
+        [[ $comp == "$cur"* ]] || continue
+        COMPREPLY+=("$compline")
+        if ((${#comp}>longest)); then
+            longest=${#comp}
+        fi
+    done < <(printf "%s\n" "${completions[@]}")
+
+    # If there is a single completion left, remove the description text
+    if ((${#COMPREPLY[*]} == 1)); then
+        __lxc_debug "COMPREPLY[0]: ${COMPREPLY[0]}"
+        comp="${COMPREPLY[0]%%$tab*}"
+        __lxc_debug "Removed description from single completion, which is now: ${comp}"
+        COMPREPLY[0]=$comp
+    else # Format the descriptions
+        __lxc_format_comp_descriptions $longest
+    fi
+}
+
+__lxc_handle_special_char()
+{
+    local comp="$1"
+    local char=$2
+    if [[ "$comp" == *${char}* && "$COMP_WORDBREAKS" == *${char}* ]]; then
+        local word=${comp%"${comp##*${char}}"}
+        local idx=${#COMPREPLY[*]}
+        while ((--idx >= 0)); do
+            COMPREPLY[idx]=${COMPREPLY[idx]#"$word"}
+        done
+    fi
+}
+
+__lxc_format_comp_descriptions()
+{
+    local tab=$'\t'
+    local comp desc maxdesclength
+    local longest=$1
+
+    local i ci
+    for ci in ${!COMPREPLY[*]}; do
+        comp=${COMPREPLY[ci]}
+        # Properly format the description string which follows a tab character if there is one
+        if [[ "$comp" == *$tab* ]]; then
+            __lxc_debug "Original comp: $comp"
+            desc=${comp#*$tab}
+            comp=${comp%%$tab*}
+
+            # $$(tput cols) stores the current shell width.
+            # Remove an extra 4 because we add 2 spaces and 2 parentheses.
+            maxdesclength=$(( $(tput cols) - longest - 4 ))
+
+            # Make sure we can fit a description of at least 8 characters
+            # if we are to align the descriptions.
+            if ((maxdesclength > 8)); then
+                # Add the proper number of spaces to align the descriptions
+                for ((i = ${#comp} ; i < longest ; i++)); do
+                    comp+=" "
+                done
+            else
+                # Don't pad the descriptions so we can fit more text after the completion
+                maxdesclength=$(( $(tput cols) - ${#comp} - 4 ))
+            fi
+
+            # If there is enough space for any description text,
+            # truncate the descriptions that are too long for the shell width
+            if ((maxdesclength > 0)); then
+                if ((${#desc} > maxdesclength)); then
+                    desc=${desc:0:$(( maxdesclength - 1 ))}
+                    desc+="…"
+                fi
+                comp+="  ($desc)"
+            fi
+            COMPREPLY[ci]=$comp
+            __lxc_debug "Final comp: $comp"
+        fi
+    done
+}
+
+__start_lxc()
+{
+    local cur prev words cword split
+
+    COMPREPLY=()
+
+    # Call _init_completion from the bash-completion package
+    # to prepare the arguments properly
+    if declare -F _init_completion >/dev/null 2>&1; then
+        _init_completion -n =: || return
+    else
+        __lxc_init_completion -n =: || return
+    fi
+
+    __lxc_debug
+    __lxc_debug "========= starting completion logic =========="
+    __lxc_debug "cur is ${cur}, words[*] is ${words[*]}, #words[@] is ${#words[@]}, cword is $cword"
+
+    # The user could have moved the cursor backwards on the command-line.
+    # We need to trigger completion from the $cword location, so we need
+    # to truncate the command-line ($words) up to the $cword location.
+    words=("${words[@]:0:$cword+1}")
+    __lxc_debug "Truncated words[*]: ${words[*]},"
+
+    local out directive
+    __lxc_get_completion_results
+    __lxc_process_completion_results
+}
+
+# Snap calls lxd.lxc under the hood, so we'll need to provide completions for both lxd.lxc and lxc.
+complete -o default -F __start_lxc lxd.lxc lxc
+
+# ex: ts=4 sw=4 et filetype=sh