lib/varstash

   1 ################################################################################
   2 # Stash/unstash support for per-directory variables
   3 #
   4 # Adopted for zsh-autoenv.
   5 #
   6 #   Copyright (c) 2009,2012 Dave Olszewski <cxreg@pobox.com>
   7 #   http://github.com/cxreg/smartcd
   8 #
   9 #   This code is released under GPL v2 and the Artistic License, and
  10 #   may be redistributed under the terms of either.
  11 #
  12 #
  13 #   This library allows you to save the current value of a given environment
  14 #   variable in a temporary location, so that you can modify it, and then
  15 #   later restore its original value.
  16 #
  17 #   Note that you will need to be in the same directory you were in when you
  18 #   stashed in order to successfully unstash.  This is because the temporary
  19 #   variable is derived from your current working directory's path.
  20 #
  21 #   Usage:
  22 #       stash PATH
  23 #       export PATH=/something/else
  24 #       [...]
  25 #       unstash PATH
  26 #
  27 #   Note that this was written for use with, and works very well with,
  28 #   smartcd.  See the documentation there for examples.
  29 #
  30 #   An alternate usage is `autostash' which will trigger autounstash when
  31 #   leaving the directory, if combined with smartcd.  This reduces the amount
  32 #   of explicit configuration you need to provide:
  33 #
  34 #       autostash PATH
  35 #       export PATH=/something/else
  36 #
  37 #   You may also do both operations on line line, leaving only the very succinct
  38 #
  39 #       autostash PATH=/something/else
  40 #
  41 #   If you attempt to stash the same value twice, a warning will be displayed
  42 #   and the second stash will not occur.  To make it happen anyway, pass -f
  43 #   as the first argument to stash.
  44 #
  45 #       $ stash FOO
  46 #       $ stash FOO
  47 #       You have already stashed FOO, please specify "-f" if you want to overwrite another stashed value
  48 #       $ stash -f FOO
  49 #       $
  50 #
  51 #   This rule is a bit different if you are assigning a value and the variable
  52 #   has already been stashed.  In that case, the new value will be assigned, but
  53 #   the stash will not be overwritten.  This allows for non-conflicting chained
  54 #   stash-assign rules.
  55 #
  56 ################################################################################
  57
  58
  59 function stash() {
  60     if [[ $1 == "-f" ]]; then
  61         local force=1; shift
  62     fi
  63
  64     while [[ -n $1 ]]; do
  65         if [[ $1 == "alias" && $2 == *=* ]]; then
  66             shift
  67             local _stashing_alias_assign=1
  68             continue
  69         fi
  70
  71         local stash_expression=$1
  72         local stash_which=${stash_expression%%'='*}
  73         local stash_name=$(_mangle_var $stash_which)
  74
  75         # Extract the value and make it double-quote safe
  76         local stash_value=${stash_expression#*'='}
  77         stash_value=${stash_value//\\/\\\\}
  78         stash_value=${stash_value//\"/\\\"}
  79         stash_value=${stash_value//\`/\\\`}
  80         stash_value=${stash_value//\$/\\\$}
  81
  82         if [[ ( -n "$(eval echo '$__varstash_alias__'$stash_name)"    ||
  83                 -n "$(eval echo '$__varstash_function__'$stash_name)" ||
  84                 -n "$(eval echo '$__varstash_array__'$stash_name)"    ||
  85                 -n "$(eval echo '$__varstash_export__'$stash_name)"   ||
  86                 -n "$(eval echo '$__varstash_variable__'$stash_name)" ||
  87                 -n "$(eval echo '$__varstash_nostash__'$stash_name)" )
  88                 && -z $force ]]; then
  89
  90             if [[ -z $already_stashed && ${already_stashed-_} == "_" ]]; then
  91                 local already_stashed=1
  92             else
  93                 already_stashed=1
  94             fi
  95
  96             if [[ $stash_which == $stash_expression ]]; then
  97                 if [[ -z $run_from_smartcd ]]; then
  98                     echo "You have already stashed $stash_which, please specify \"-f\" if you want to overwrite another stashed value"
  99                 fi
 100
 101                 # Skip remaining work if we're not doing an assignment
 102                 shift
 103                 continue
 104             fi
 105         fi
 106
 107         # Handle any alias that may exist under this name
 108         if [[ -z $already_stashed ]]; then
 109             local alias_def="$(eval alias $stash_which 2>/dev/null)"
 110             if [[ -n $alias_def ]]; then
 111                 alias_def=${alias_def#alias }
 112                 eval "__varstash_alias__$stash_name=\"$alias_def\""
 113                 local stashed=1
 114             fi
 115         fi
 116         if [[ $stash_which != $stash_expression && -n $_stashing_alias_assign ]]; then
 117             eval "alias $stash_which=\"$stash_value\""
 118         fi
 119
 120         # Handle any function that may exist under this name
 121         if [[ -z $already_stashed ]]; then
 122             local function_def="$(declare -f $stash_which)"
 123             if [[ -n $function_def ]]; then
 124                 # make function definition quote-safe.  because we are going to evaluate the
 125                 # source with "echo -e", we need to double-escape the backslashes (so 1 -> 4)
 126                 function_def=${function_def//\\/\\\\\\\\}
 127                 function_def=${function_def//\"/\\\"}
 128                 function_def=${function_def//\`/\\\`}
 129                 function_def=${function_def//\$/\\\$}
 130                 eval "__varstash_function__$stash_name=\"$function_def\""
 131                 local stashed=1
 132             fi
 133         fi
 134
 135         # Handle any variable that may exist under this name
 136         local vartype="$(declare -p $stash_which 2>/dev/null)"
 137         if [[ -n $vartype ]]; then
 138             if [[ $vartype == 'typeset -a'* ]]; then
 139                 # varible is an array
 140                 if [[ -z $already_stashed ]]; then
 141                     eval "__varstash_array__$stash_name=(\"\${$stash_which""[@]}\")"
 142                 fi
 143
 144             elif [[ $vartype == "export "* || $vartype == 'typeset -x'* ]]; then
 145                 # variable is exported
 146                 if [[ -z $already_stashed ]]; then
 147                     eval "export __varstash_export__$stash_name=\"\$$stash_which\""
 148                 fi
 149                 if [[ $stash_which != $stash_expression && -z $_stashing_alias_assign ]]; then
 150                     eval "export $stash_which=\"$stash_value\""
 151                 fi
 152             else
 153                 # regular variable
 154                 if [[ -z $already_stashed ]]; then
 155                     eval "__varstash_variable__$stash_name=\"\$$stash_which\""
 156                 fi
 157                 if [[ $stash_which != $stash_expression && -z $_stashing_alias_assign ]]; then
 158                     eval "$stash_which=\"$stash_value\""
 159                 fi
 160
 161             fi
 162             local stashed=1
 163         fi
 164
 165         if [[ -z $stashed ]]; then
 166             # Nothing in the variable we're stashing, but make a note that we stashed so we
 167             # do the right thing when unstashing.  Without this, we take no action on unstash
 168
 169             # Zsh bug sometimes caues
 170             # (eval):1: command not found: __varstash_nostash___tmp__home_dolszewski_src_smartcd_RANDOM_VARIABLE=1
 171             # fixed in zsh commit 724fd07a67f, version 4.3.14
 172             if [[ -z $already_stashed ]]; then
 173                 eval "export __varstash_nostash__$stash_name=1"
 174             fi
 175
 176             # In the case of a previously unset variable that we're assigning too, export it
 177             if [[ $stash_which != $stash_expression && -z $_stashing_alias_assign ]]; then
 178                 eval "export $stash_which=\"$stash_value\""
 179             fi
 180         fi
 181
 182         shift
 183         unset -v _stashing_alias_assign
 184     done
 185 }
 186
 187 function get_autostash_array_name() {
 188     local autostash_name=$(_mangle_var AUTOSTASH)
 189     # Create a scalar variable linked to an array (for exporting).
 190     local autostash_array_name=${(L)autostash_name}
 191     if ! (( ${(P)+autostash_array_name} )); then
 192         # Conditionally set it, to prevent error with Zsh 4.3:
 193         # can't tie already tied scalar: ...
 194         typeset -xT $autostash_name $autostash_array_name
 195     fi
 196     ret=$autostash_array_name
 197 }
 198
 199 function autostash() {
 200     local run_from_autostash=1
 201     while [[ -n $1 ]]; do
 202         if [[ $1 == "alias" && $2 == *=* ]]; then
 203             shift
 204             local _stashing_alias_assign=1
 205         fi
 206
 207         local already_stashed=
 208         stash "$1"
 209         if [[ -z $already_stashed ]]; then
 210             local ret varname=${1%%'='*}
 211             get_autostash_array_name
 212             eval "$ret=(\$$ret \$varname)"
 213         fi
 214         shift
 215         unset -v _stashing_alias_assign
 216     done
 217 }
 218
 219 function unstash() {
 220     while [[ -n $1 ]]; do
 221         local unstash_which=$1
 222         if [[ -z $unstash_which ]]; then
 223             continue
 224         fi
 225
 226         local unstash_name=$(_mangle_var $unstash_which)
 227
 228         # This bit is a little tricky.  Here are the rules:
 229         #   1) unstash any alias, function, or variable which matches
 230         #   2) if one or more matches, but not all, delete any that did not
 231         #   3) if none match but nostash is found, delete all
 232         #   4) if none match and nostash not found, do nothing
 233
 234         # Unstash any alias
 235         if [[ -n "$(eval echo \$__varstash_alias__$unstash_name)" ]]; then
 236             eval "alias $(eval echo \$__varstash_alias__$unstash_name)"
 237             unset __varstash_alias__$unstash_name
 238             local unstashed=1
 239             local unstashed_alias=1
 240         fi
 241
 242         # Unstash any function
 243         if [[ -n "$(eval echo \$__varstash_function__$unstash_name)" ]]; then
 244             eval "function $(eval echo -e \"\$__varstash_function__$unstash_name\")"
 245             unset __varstash_function__$unstash_name
 246             local unstashed=1
 247             local unstashed_function=1
 248         fi
 249
 250         # Unstash any variable
 251         if [[ -n "$(declare -p __varstash_array__$unstash_name 2>/dev/null)" ]]; then
 252             eval "$unstash_which=(\"\${__varstash_array__$unstash_name""[@]}\")"
 253             unset __varstash_array__$unstash_name
 254             local unstashed=1
 255             local unstashed_variable=1
 256         elif [[ -n "$(declare -p __varstash_export__$unstash_name 2>/dev/null)" ]]; then
 257             eval "export $unstash_which=\"\$__varstash_export__$unstash_name\""
 258             unset __varstash_export__$unstash_name
 259             local unstashed=1
 260             local unstashed_variable=1
 261         elif [[ -n "$(declare -p __varstash_variable__$unstash_name 2>/dev/null)" ]]; then
 262             # Unset variable first to reset export
 263             unset -v $unstash_which
 264             eval "$unstash_which=\"\$__varstash_variable__$unstash_name\""
 265             unset __varstash_variable__$unstash_name
 266             local unstashed=1
 267             local unstashed_variable=1
 268         fi
 269
 270         # Unset any values which did not exist at time of stash
 271         local nostash="$(eval echo \$__varstash_nostash__$unstash_name)"
 272         unset __varstash_nostash__$unstash_name
 273         if [[ ( -n "$nostash" && -z "$unstashed" ) || ( -n "$unstashed" && -z "$unstashed_alias" ) ]]; then
 274             unalias $unstash_which 2>/dev/null
 275         fi
 276         if [[ ( -n "$nostash" && -z "$unstashed" ) || ( -n "$unstashed" && -z "$unstashed_function" ) ]]; then
 277             unset -f $unstash_which 2>/dev/null
 278         fi
 279         if [[ ( -n "$nostash" && -z "$unstashed" ) || ( -n "$unstashed" && -z "$unstashed_variable" ) ]]; then
 280             # Don't try to unset illegal variable names
 281             # Using substitution to avoid using regex, which might fail to load on Zsh (minimal system).
 282             if [[ ${unstash_which//[^a-zA-Z0-9_]/} == $unstash_which && $unstash_which != [0-9]* ]]; then
 283                 unset -v $unstash_which
 284             fi
 285         fi
 286
 287         shift
 288     done
 289 }
 290
 291 function autounstash() {
 292     # If there is anything in (mangled) variable AUTOSTASH, then unstash it
 293     local ret
 294     get_autostash_array_name
 295     if (( ${#${(P)ret}} > 0 )); then
 296         local run_from_autounstash=1
 297         for autounstash_var in ${(P)ret}; do
 298             unstash $autounstash_var
 299         done
 300         unset $ret
 301     fi
 302 }
 303
 304 function _mangle_var() {
 305     local mangle_var_where="${varstash_dir:-$PWD}"
 306     mangle_var_where=${mangle_var_where//[^A-Za-z0-9]/_}
 307     local mangled_name=${1//[^A-Za-z0-9]/_}
 308     echo "_tmp_${mangle_var_where}_${mangled_name}"
 309 }
 310
 311 # vim: filetype=zsh autoindent expandtab shiftwidth=4 softtabstop=4