1 files changed, 234 insertions, 0 deletions
diff --git a/nixos/modules/installer/tools/nixos-option.sh b/nixos/modules/installer/tools/nixos-option.sh
new file mode 100644
index 000000000000..60cee2519da0
--- /dev/null
+++ b/nixos/modules/installer/tools/nixos-option.sh
@@ -0,0 +1,234 @@
+#! @shell@ -e
+
+# FIXME: rewrite this in a more suitable language.
+
+usage () {
+    exec man nixos-option
+    exit 1
+}
+
+#####################
+# Process Arguments #
+#####################
+
+desc=false
+defs=false
+value=false
+xml=false
+verbose=false
+
+option=""
+
+argfun=""
+for arg; do
+  if test -z "$argfun"; then
+    case $arg in
+      -*)
+        longarg=""
+        sarg="$arg"
+        while test "$sarg" != "-"; do
+          case $sarg in
+            --*) longarg=$arg; sarg="--";;
+            -d*) longarg="$longarg --description";;
+            -v*) longarg="$longarg --value";;
+            -l*) longarg="$longarg --lookup";;
+            -*) usage;;
+          esac
+          # remove the first letter option
+          sarg="-${sarg#??}"
+        done
+        ;;
+      *) longarg=$arg;;
+    esac
+    for larg in $longarg; do
+      case $larg in
+        --description) desc=true;;
+        --value) value=true;;
+        --lookup) defs=true;;
+        --xml) xml=true;;
+        --verbose) verbose=true;;
+        --help) usage;;
+        -*) usage;;
+        *) if test -z "$option"; then
+             option="$larg"
+           else
+             usage
+           fi;;
+      esac
+    done
+  else
+    case $argfun in
+      set_*)
+        var=$(echo $argfun | sed 's,^set_,,')
+        eval $var=$arg
+        ;;
+    esac
+    argfun=""
+  fi
+done
+
+if $xml; then
+  value=true
+  desc=true
+  defs=true
+fi
+
+if ! $defs && ! $desc; then
+  value=true
+fi
+
+if $verbose; then
+  set -x
+else
+  set +x
+fi
+
+#############################
+# Process the configuration #
+#############################
+
+evalNix(){
+  nix-instantiate - --eval-only "$@"
+}
+
+evalAttr(){
+  local prefix="$1"
+  local strict="$2"
+  local suffix="$3"
+  echo "(import <nixos> {}).$prefix${option:+.$option}${suffix:+.$suffix}" |
+    evalNix ${strict:+--strict}
+}
+
+evalOpt(){
+  evalAttr "options" "" "$@"
+}
+
+evalCfg(){
+  local strict="$1"
+  evalAttr "config" "$strict"
+}
+
+findSources(){
+  local suffix=$1
+  echo "(import <nixos> {}).options${option:+.$option}.$suffix" |
+    evalNix --strict
+}
+
+# Given a result from nix-instantiate, recover the list of attributes it
+# contains.
+attrNames() {
+  local attributeset=$1
+  # sed is used to replace un-printable subset by 0s, and to remove most of
+  # the inner-attribute set, which reduce the likelyhood to encounter badly
+  # pre-processed input.
+  echo "builtins.attrNames $attributeset" | \
+    sed 's,<[A-Z]*>,0,g; :inner; s/{[^\{\}]*};/0;/g; t inner;' | \
+    evalNix --strict
+}
+
+# map a simple list which contains strings or paths.
+nixMap() {
+  local fun="$1"
+  local list="$2"
+  local elem
+  for elem in $list; do
+    test $elem = '[' -o $elem = ']' && continue;
+    $fun $elem
+  done
+}
+
+# This duplicates the work made below, but it is useful for processing
+# the output of nixos-option with other tools such as nixos-gui.
+if $xml; then
+  evalNix --xml --no-location <<EOF
+let
+  reach = attrs: attrs${option:+.$option};
+  nixos = import <nixos> {};
+  nixpkgs = import <nixpkgs> {};
+  sources = builtins.map (f: f.source);
+  opt = reach nixos.options;
+  cfg = reach nixos.config;
+in
+
+with nixpkgs.lib;
+
+let
+  optStrict = v:
+    let
+      traverse = x :
+        if isAttrs x then
+          if x ? outPath then true
+          else all id (mapAttrsFlatten (n: traverseNoAttrs) x)
+        else traverseNoAttrs x;
+      traverseNoAttrs = x:
+        # do not continue in attribute sets
+        if isAttrs x then true
+        else if isList x then all id (map traverse x)
+        else true;
+    in assert traverse v; v;
+in
+
+if isOption opt then
+  optStrict ({}
+  // optionalAttrs (opt ? default) { inherit (opt) default; }
+  // optionalAttrs (opt ? example) { inherit (opt) example; }
+  // optionalAttrs (opt ? description) { inherit (opt) description; }
+  // optionalAttrs (opt ? type) { typename = opt.type.name; }
+  // optionalAttrs (opt ? options) { inherit (opt) options; }
+  // {
+    # to disambiguate the xml output.
+    _isOption = true;
+    declarations = sources opt.declarations;
+    definitions = sources opt.definitions;
+    value = cfg;
+  })
+else
+  opt
+EOF
+  exit $?
+fi
+
+if test "$(evalOpt "_type" 2> /dev/null)" = '"option"'; then
+  $value && evalCfg 1
+
+  if $desc; then
+    $value && echo;
+
+    if default=$(evalOpt "default" - 2> /dev/null); then
+      echo "Default: $default"
+    else
+      echo "Default: <None>"
+    fi
+    if example=$(evalOpt "example" - 2> /dev/null); then
+      echo "Example: $example"
+    fi
+    echo "Description:"
+    eval printf $(evalOpt "description")
+  fi
+
+  if $defs; then
+    $desc || $value && echo;
+
+    printPath () { echo "  $1"; }
+
+    echo "Declared by:"
+    nixMap printPath "$(findSources "declarations")"
+    echo ""
+    echo "Defined by:"
+    nixMap printPath "$(findSources "files")"
+    echo ""
+  fi
+
+else
+  # echo 1>&2 "Warning: This value is not an option."
+
+  result=$(evalCfg "")
+  if names=$(attrNames "$result" 2> /dev/null); then
+    echo 1>&2 "This attribute set contains:"
+    escapeQuotes () { eval echo "$1"; }
+    nixMap escapeQuotes "$names"
+  else
+    echo 1>&2 "An error occured while looking for attribute names."
+    echo $result
+  fi
+fi