Autocomplete in make based on possible targets

Question

The Makefile is:

%.pdf: %.tex
    rubber -d $<

If there is a doc.tex in the directory, then make doc.pdf builds doc.pdf. The problem is that when I type make, the autocompletion gives nothing: it doesn't even allow to autocomplete to make doc.tex. What can be done about it?

Answer 1

The bash-completion package doesn't do this, it does some acrobatics to handle both command line options and extract a list of Makefile targets, but it does not try to generate matches by applying wildcards or otherwise handling any pattern rules.

It can be done however, here's a simple version with a few caveats.

function _mkcache() {
    local _file="$1"
    # add "-r" to omit defaults (60+ rules)
    ${MAKE:-make} ${_file:+-f "$_file"} -qp 2>/dev/null |
    gawk '/^# *Make data base/,/^# *Finished Make data base/{
      if (/^# Not a target/) { getline; next }
      ## handle "target: ..."
      if (match($0,/^([^.#% ][^:%=]+) *:($|[^=])(.*)/,bits)) {
          #if (bits[3]=="") next # OPT: skip phony
          printf("%s\n",bits[1])
      }
      ## handle "%.x [...]: %.y [| x]", split into distinct targets/prereqs
      else if (match($0,/^([^:]*%[^:]*) *(::?) *(.*%.*) *(\| *(.*))?/,bits)) {
          #if (bits[3]=="%") next # OPT: skip wildcard ones
          nb1=split(bits[1],bb1)
          nb3=split(bits[3],bb3)
          for (nn=1; nn<=nb1; nn++) 
            for (mm=1; mm<=nb3; mm++) 
              printf("%s : %s\n",bb1[nn],bb3[mm])
      }
      ## handle fixed (no %) deps
      else if (match($0,/^([^:]*%[^:]*) *(::?) *([^%]*)$/,bits)) {
          if (bits[3]=="") next # phony
          printf("%s : %s\n",bits[1],bits[3])
      }
      ## handle old form ".c.o:"  rewrite to new form "%.o: %.c"
      else if (match($0,/^\.([^.]+)\.([^.]+): *(.*)/,bits)) {
          printf("%%.%s : %%.%s\n", bits[2],bits[1])
      }
    }' > ".${_file:-Makefile}.targets"
}

function _bc_make() {
    local ctok=${COMP_WORDS[COMP_CWORD]}   # curr token
    local ptok=${COMP_WORDS[COMP_CWORD-1]} # prev token
    local -a mkrule maybe
    local try rr lhs rhs rdir pat makefile=Makefile

    ## check we're not doing any make options 
    [[ ${ctok:0:1} != "-" && ! $ptok =~ ^-[fCIjloW] ]] && {
        COMPREPLY=()
        [[ "$makefile" -nt .${makefile}.targets ]] && 
            _mkcache "$makefile"

        mapfile -t mkrule < ".${makefile}.targets"
        # mkrule+=( "%.o : %.c" )  # stuff in extra rules

        for rr in "${mkrule[@]}"; do
            IFS=": " read lhs rhs <<< $rr

            ## special "archive(member):"
            [[ "$lhs" =~ ^(.*)?\((.+)\) ]] && {
                continue # not handled
            }

            ## handle simple targets
            [[ "$rhs" == "" ]] && {
                COMPREPLY+=( $(compgen -W "$lhs" -- "$ctok" ) )
                continue
            }

            ## rules with a path, like "% : RCS/%,v" 
            rdir=""
            [[ "$rhs" == */* ]] && rdir="${rhs/%\/*/}/" 
            rhs=${rhs/#*\//}

            ## expand (glob) that matches RHS 
            ## if current token already ends in a "." strip it
            ## match by replacing "%" stem with "*"

            [[ $ctok == *. ]] && try="${rdir}${rhs/\%./$ctok*}" \
                              || try="${rdir}${rhs/\%/$ctok*}"

            maybe=( $(compgen -G "$try") )  # try must be quoted

            ## maybe[] is an array of filenames from expanded prereq globs
            (( ${#maybe[*]} )) && {

               [[ "$rhs" =~ % ]] && {
                   ## promote rhs glob to a regex: % -> (.*)
                   rhs="${rhs/./\\.}"
                   pat="${rdir}${rhs/\%/(.*)}"

                   ## use regex to extract stem from RHS, sub "%" on LHS
                   for nn in "${maybe[@]}"; do 
                       [[ $nn =~ $pat ]] && {
                           COMPREPLY+=( "${lhs/\%/${BASH_REMATCH[1]}}" )
                       }
                   done
               } || {
                   # fixed prereqs (no % on RHS)
                   COMPREPLY+=( "${lhs/\%/$ctok}" )   
               }
            }
        done
        return
    }
    COMPREPLY=() #default
}
complete -F _bc_make ${MAKE:-make}

There are two parts, a function _mkcache extracts all the rules and targets from a Makefile and caches these. It also does a bit of processing so the rules are simplified to a single "target : pre-req" form in that cache.

Then, a completion function _bc_make takes the token you attempt completion on and tries to match against targets, and uses the pattern rules to expand a glob based on the pre-requisites and the word for completion. If one or more matches are found, it builds a list of targets based on the pattern rules.

GNU make is assumed. It should correctly handle:

• targets and pattern rules (though not all of them, see below)
• new and old form .c.o → %.o : %.c
• paths in prereqs (e.g RCS/)
• with or without all default rules (add -r to make if preferred)

Caveats, and not supported:

• intermediate or chained dependencies, it's not as smart as make
• VPATH or vpath
• .SUFFIXES
• make -C dir
• "archive(member)" targets, explicit or implicit
• make options expansion
• pathological junk in the environment that can cause Makefile parsing problems (TERMCAP for example)
• Makefiles named other than Makefile

Some of the above can be added relatively simply, others like archive handling are not so simple.