1 files changed, 139 insertions, 54 deletions
diff --git a/nixos/modules/installer/tools/nixos-option.sh b/nixos/modules/installer/tools/nixos-option.sh
index edc94d73208..17c17d05e28 100644
--- a/nixos/modules/installer/tools/nixos-option.sh
+++ b/nixos/modules/installer/tools/nixos-option.sh
@@ -11,11 +11,9 @@ usage () {
 # Process Arguments #
 #####################
 
-desc=false
-defs=false
-value=false
 xml=false
 verbose=false
+nixPath=""
 
 option=""
 
@@ -24,14 +22,12 @@ for arg; do
   if test -z "$argfun"; then
     case $arg in
       -*)
-        longarg=""
         sarg="$arg"
+        longarg=""
         while test "$sarg" != "-"; do
           case $sarg in
             --*) longarg=$arg; sarg="--";;
-            -d*) longarg="$longarg --description";;
-            -v*) longarg="$longarg --value";;
-            -l*) longarg="$longarg --lookup";;
+            -I) argfun="include_nixpath";;
             -*) usage;;
           esac
           # remove the first letter option
@@ -42,9 +38,6 @@ for arg; do
     esac
     for larg in $longarg; do
       case $larg in
-        --description) desc=true;;
-        --value) value=true;;
-        --lookup) defs=true;;
         --xml) xml=true;;
         --verbose) verbose=true;;
         --help) usage;;
@@ -62,21 +55,14 @@ for arg; do
         var=$(echo $argfun | sed 's,^set_,,')
         eval $var=$arg
         ;;
+      include_nixpath)
+        nixPath="-I $arg $nixPath"
+        ;;
     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
@@ -88,19 +74,114 @@ fi
 #############################
 
 evalNix(){
-  nix-instantiate - --eval-only "$@"
+  result=$(nix-instantiate ${nixPath:+$nixPath} - --eval-only "$@" 2>&1)
+  if test $? -eq 0; then
+      cat <<EOF
+$result
+EOF
+      return 0;
+  else
+      sed -n '
+  /^error/ { s/, at (string):[0-9]*:[0-9]*//; p; };
+  /^warning: Nix search path/ { p; };
+' <<EOF
+$result
+EOF
+      return 1;
+  fi
+}
+
+header="let
+  nixos = import <nixpkgs/nixos> {};
+  nixpkgs = import <nixpkgs> {};
+in with nixpkgs.lib;
+"
+
+# This function is used for converting the option definition path given by
+# the user into accessors for reaching the definition and the declaration
+# corresponding to this option.
+generateAccessors(){
+  if result=$(evalNix --strict --show-trace <<EOF
+$header
+
+let
+  path = "${option:+$option}";
+  pathList = splitString "." path;
+
+  walkOptions = attrsNames: result:
+    if attrsNames == [] then
+      result
+    else
+      let name = head attrsNames; rest = tail attrsNames; in
+      if isOption result.options then
+        walkOptions rest {
+          options = result.options.type.getSubOptions "";
+          opt = ''(\${result.opt}.type.getSubOptions "")'';
+          cfg = ''\${result.cfg}."\${name}"'';
+        }
+      else
+        walkOptions rest {
+          options = result.options.\${name};
+          opt = ''\${result.opt}."\${name}"'';
+          cfg = ''\${result.cfg}."\${name}"'';
+        }
+    ;
+
+  walkResult = (if path == "" then x: x else walkOptions pathList) {
+    options = nixos.options;
+    opt = ''nixos.options'';
+    cfg = ''nixos.config'';
+  };
+
+in
+  ''let option = \${walkResult.opt}; config = \${walkResult.cfg}; in''
+EOF
+)
+  then
+      echo $result
+  else
+      # In case of error we want to ignore the error message roduced by the
+      # script above, as it is iterating over each attribute, which does not
+      # produce a nice error message.  The following code is a fallback
+      # solution which is cause a nicer error message in the next
+      # evaluation.
+      echo "\"let option = nixos.options${option:+.$option}; config = nixos.config${option:+.$option}; in\""
+  fi
 }
 
+header="$header
+$(eval echo $(generateAccessors))
+"
+
 evalAttr(){
   local prefix="$1"
   local strict="$2"
   local suffix="$3"
-  echo "(import <nixos> {}).$prefix${option:+.$option}${suffix:+.$suffix}" |
-    evalNix ${strict:+--strict}
+
+  # If strict is set, then set it to "true".
+  test -n "$strict" && strict=true
+
+  evalNix ${strict:+--strict} <<EOF
+$header
+
+let
+  value = $prefix${suffix:+.$suffix};
+  strict = ${strict:-false};
+  cleanOutput = x: with nixpkgs.lib;
+    if isDerivation x then x.outPath
+    else if isFunction x then "<CODE>"
+    else if strict then
+      if isAttrs x then mapAttrs (n: cleanOutput) x
+      else if isList x then map cleanOutput x
+      else x
+    else x;
+in
+  cleanOutput value
+EOF
 }
 
 evalOpt(){
-  evalAttr "options" "" "$@"
+  evalAttr "option" "" "$@"
 }
 
 evalCfg(){
@@ -110,8 +191,11 @@ evalCfg(){
 
 findSources(){
   local suffix=$1
-  echo "(import <nixos> {}).options${option:+.$option}.$suffix" |
-    evalNix --strict
+  evalNix --strict <<EOF
+$header
+
+option.$suffix
+EOF
 }
 
 # Given a result from nix-instantiate, recover the list of attributes it
@@ -141,13 +225,12 @@ nixMap() {
 # the output of nixos-option with other tools such as nixos-gui.
 if $xml; then
   evalNix --xml --no-location <<EOF
+$header
+
 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;
+  opt = option;
+  cfg = config;
 in
 
 with nixpkgs.lib;
@@ -189,35 +272,37 @@ EOF
 fi
 
 if test "$(evalOpt "_type" 2> /dev/null)" = '"option"'; then
-  $value && evalCfg 1
+  echo "Value:"
+  evalCfg 1
 
-  if $desc; then
-    $value && echo;
+  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 $(evalOpt "description")
+  echo "Default:"
+  if default=$(evalOpt "default" - 2> /dev/null); then
+    echo "$default"
+  else
+    echo "<None>"
   fi
+  echo
+  if example=$(evalOpt "example" - 2> /dev/null); then
+    echo "Example:"
+    echo "$example"
+    echo
+  fi
+  echo "Description:"
+  echo
+  eval printf $(evalOpt "description")
 
-  if $defs; then
-    $desc || $value && echo;
+  echo $desc;
 
-    printPath () { echo "  $1"; }
+  printPath () { echo "  $1"; }
 
-    echo "Declared by:"
-    nixMap printPath "$(findSources "declarations")"
-    echo ""
-    echo "Defined by:"
-    nixMap printPath "$(findSources "files")"
-    echo ""
-  fi
+  echo "Declared by:"
+  nixMap printPath "$(findSources "declarations")"
+  echo
+  echo "Defined by:"
+  nixMap printPath "$(findSources "files")"
+  echo
 
 else
   # echo 1>&2 "Warning: This value is not an option."