* Added an experimental feature suggested by Andres: ellipses ("...")

in attribute set pattern matches.  This allows defining a function
  that takes *at least* the listed attributes, while ignoring
  additional attributes.  For instance,

    {stdenv, fetchurl, fuse, ...}:
    
    stdenv.mkDerivation {
      ...
    };
    
  defines a function that requires an attribute set that contains the 
  specified attributes but ignores others.  The main advantage is that
  we can then write in all-packages.nix

    aefs = import ../bla/aefs pkgs;

  instead of

    aefs = import ../bla/aefs {
      inherit stdenv fetchurl fuse;
    };

  This saves a lot of typing (not to mention not having to update
  all-packages.nix with purely mechanical changes).  It saves as much
  typing as the "args: with args;" style, but has the advantage that
  the function arguments are properly declared (not implicit in what
  the body of the "with" uses).

src/libexpr/eval.cc

@@ -84,11 +84,12 @@ static void patternMatch(EvalState & state,
     ATerm name;
     ATermList formals;
     Pattern pat1, pat2;
+    ATermBool ellipsis;
     
     if (matchVarPat(pat, name)) 
         subs.set(name, arg);
 
-    else if (matchAttrsPat(pat, formals)) {
+    else if (matchAttrsPat(pat, formals, ellipsis)) {
 
         arg = evalExpr(state, arg);
 
@@ -122,8 +123,8 @@ static void patternMatch(EvalState & state,
         }
 
         /* Check that each actual argument is listed as a formal
-           argument. */
+           argument (unless the attribute match specifies a `...'). */
-        if (attrsUsed != nrAttrs)
+        if (ellipsis == eFalse && attrsUsed != nrAttrs)
             throw TypeError(format("the function does not expect an argument named `%1%'")
                 % aterm2String(attrs.begin()->key));
     }
@@ -402,9 +403,10 @@ Expr autoCallFunction(Expr e, const ATermMap & args)
     Pattern pat;
     ATerm body, pos;
     ATermList formals;
-
+    ATermBool ellipsis;
+    
     /* !!! this should be more general */
-    if (matchFunction(e, pat, body, pos) && matchAttrsPat(pat, formals)) {
+    if (matchFunction(e, pat, body, pos) && matchAttrsPat(pat, formals, ellipsis)) {
         ATermMap actualArgs(ATgetLength(formals));
         
         for (ATermIterator i(formals); i; ++i) {

src/libexpr/expr-to-xml.cc

@@ -45,15 +45,17 @@ static void printPatternAsXML(Pattern pat, XMLWriter & doc)
     ATerm name;
     ATermList formals;
     Pattern pat1, pat2;
+    ATermBool ellipsis;
     if (matchVarPat(pat, name))
         doc.writeEmptyElement("varpat", singletonAttrs("name", aterm2String(name)));
-    else if (matchAttrsPat(pat, formals)) {
+    else if (matchAttrsPat(pat, formals, ellipsis)) {
         XMLOpenElement _(doc, "attrspat");
         for (ATermIterator i(formals); i; ++i) {
             Expr name; ATerm dummy;
             if (!matchFormal(*i, name, dummy)) abort();
             doc.writeEmptyElement("attr", singletonAttrs("name", aterm2String(name)));
         }
+        if (ellipsis == eTrue) doc.writeEmptyElement("ellipsis");
     }
     else if (matchAtPat(pat, pat1, pat2)) {
         XMLOpenElement _(doc, "at");

src/libexpr/lexer.l

@@ -95,6 +95,7 @@ let         { return LET; }
 in          { return IN; }
 rec         { return REC; }
 inherit     { return INHERIT; }
+\.\.\.      { return ELLIPSIS; }
 
 \=\=        { return EQ; }
 \!\=        { return NEQ; }

src/libexpr/nixexpr-ast.def

@@ -66,7 +66,7 @@ PrimOp | int ATermBlob ATermList | Expr |
 Attrs | ATermList | Expr |
 Closed | Expr | Expr |
 Rec | ATermList ATermList | Expr |
-Bool | ATerm | Expr |
+Bool | ATermBool | Expr |
 Null | | Expr |
 
 Bind | string Expr Pos | ATerm |
@@ -76,7 +76,7 @@ Inherit | Expr ATermList Pos | ATerm |
 Scope | | Expr |
 
 VarPat | string | Pattern |
-AttrsPat | ATermList | Pattern |
+AttrsPat | ATermList ATermBool | Pattern | # bool = `...'
 AtPat | Pattern Pattern | Pattern |
 
 Formal | string DefaultValue | ATerm |
@@ -84,8 +84,8 @@ Formal | string DefaultValue | ATerm |
 DefaultValue | Expr | DefaultValue |
 NoDefaultValue | | DefaultValue |
 
-True | | ATerm |
+True | | ATermBool |
-False | | ATerm |
+False | | ATermBool |
 
 PrimOpDef | int ATermBlob | ATerm |
 

src/libexpr/nixexpr.cc

@@ -114,12 +114,13 @@ static void varsBoundByPattern(ATermMap & map, Pattern pat)
 {
     ATerm name;
     ATermList formals;
-    Pattern pat1, pat2;    
+    Pattern pat1, pat2;
+    ATermBool ellipsis;
     /* Use makeRemoved() so that it can be used directly in
        substitute(). */
     if (matchVarPat(pat, name))
         map.set(name, makeRemoved());
-    else if (matchAttrsPat(pat, formals)) { 
+    else if (matchAttrsPat(pat, formals, ellipsis)) { 
         for (ATermIterator i(formals); i; ++i) {
             ATerm d1;
             if (!matchFormal(*i, name, d1)) abort();

src/libexpr/nixexpr.hh

@@ -24,6 +24,7 @@ typedef ATerm Expr;
 typedef ATerm DefaultValue;
 typedef ATerm Pos;
 typedef ATerm Pattern;
+typedef ATerm ATermBool;
 
 
 /* A STL vector of ATerms.  Should be used with great care since it's

src/libexpr/parser.y

@@ -208,16 +208,22 @@ static void freeAndUnprotect(void * p)
 %union {
   ATerm t;
   ATermList ts;
+  struct {
+    ATermList formals;
+    bool ellipsis;
+  } formals;
 }
 
 %type <t> start expr expr_function expr_if expr_op
 %type <t> expr_app expr_select expr_simple bind inheritsrc formal
 %type <t> pattern pattern2
-%type <ts> binds ids expr_list formals string_parts ind_string_parts
+%type <ts> binds ids expr_list string_parts ind_string_parts
+%type <formals> formals
 %token <t> ID INT STR IND_STR PATH URI
 %token IF THEN ELSE ASSERT WITH LET IN REC INHERIT EQ NEQ AND OR IMPL
 %token DOLLAR_CURLY /* == ${ */
 %token IND_STRING_OPEN IND_STRING_CLOSE
+%token ELLIPSIS
 
 %nonassoc IMPL
 %left OR
@@ -326,7 +332,7 @@ pattern
 
 pattern2
   : ID { $$ = makeVarPat($1); }
-  | '{' formals '}' { $$ = makeAttrsPat($2); }
+  | '{' formals '}' { $$ = makeAttrsPat($2.formals, $2.ellipsis ? eTrue : eFalse); }
   ;
 
 binds
@@ -357,9 +363,14 @@ expr_list
   ;
 
 formals
-  : formal ',' formals { $$ = ATinsert($3, $1); } /* idem - right recursive */
+  : formal ',' formals /* idem - right recursive */
-  | formal { $$ = ATinsert(ATempty, $1); }
+    { $$.formals = ATinsert($3.formals, $1); $$.ellipsis = $3.ellipsis; }
-  | { $$ = ATempty; }
+  | formal
+    { $$.formals = ATinsert(ATempty, $1); $$.ellipsis = false; }
+  |
+    { $$.formals = ATempty; $$.ellipsis = false; }
+  | ELLIPSIS
+    { $$.formals = ATempty; $$.ellipsis = true; }
   ;
 
 formal
@@ -401,13 +412,14 @@ static void checkPatternVars(ATerm pos, ATermMap & map, Pattern pat)
     ATerm name;
     ATermList formals;
     Pattern pat1, pat2;
+    ATermBool ellipsis;
     if (matchVarPat(pat, name)) {
         if (map.get(name))
             throw EvalError(format("duplicate formal function argument `%1%' at %2%")
                 % aterm2String(name) % showPos(pos));
         map.set(name, name);
     }
-    else if (matchAttrsPat(pat, formals)) { 
+    else if (matchAttrsPat(pat, formals, ellipsis)) { 
         for (ATermIterator i(formals); i; ++i) {
             ATerm d1;
             if (!matchFormal(*i, name, d1)) abort();

tests/lang/eval-okay-patterns.exp

@@ -1 +1 @@
-Str("abcxyzDDDDEFgh",[])
+Str("abcxyzDDDDEFghijk",[])

tests/lang/eval-okay-patterns.nix

@@ -8,9 +8,12 @@ let
 
   i = args@args2: args.x + args2.y;
 
+  j = {x, y, z, ...}: x + y + z;
+
 in
   f {x = "a"; y = "b"; z = "c";} +
   g {x = "x"; y = "y"; z = "z";} +
   h {x = "D";} +
   h {x = "D"; y = "E"; z = "F";} +
-  i {x = "g"; y = "h";}
+  i {x = "g"; y = "h";} +
+  j {x = "i"; y = "j"; z = "k"; bla = "bla"; foo = "bar";}

tests/lang/eval-okay-xml.exp.xml

@@ -22,6 +22,16 @@
     <attr name="c">
       <string value="foobar" />
     </attr>
+    <attr name="ellipsis">
+      <function>
+        <attrspat>
+          <attr name="x" />
+          <attr name="y" />
+          <attr name="z" />
+          <ellipsis />
+        </attrspat>
+      </function>
+    </attr>
     <attr name="f">
       <function>
         <attrspat>

tests/lang/eval-okay-xml.nix

@@ -14,4 +14,6 @@ rec {
 
   at = args@{x, y, z}: x;
 
+  ellipsis = {x, y, z, ...}: x;
+
 }

tests/lang/parse-okay-1.exp

@@ -1 +1 @@
-Function(AttrsPat([Formal("x",NoDefaultValue),Formal("y",NoDefaultValue),Formal("z",NoDefaultValue)]),OpPlus(OpPlus(Var("x"),Var("y")),Var("z")),NoPos)
+Function(AttrsPat([Formal("x",NoDefaultValue),Formal("y",NoDefaultValue),Formal("z",NoDefaultValue)],Bool(False)),OpPlus(OpPlus(Var("x"),Var("y")),Var("z")),NoPos)

tests/lang/parse-okay-regression-20041027.exp

@@ -1 +1 @@
-Function(AttrsPat([Formal("stdenv",NoDefaultValue),Formal("fetchurl",NoDefaultValue)]),Call(Select(Var("stdenv"),"mkDerivation"),Attrs([Bind("name",Str("libXi-6.0.1",[]),NoPos),Bind("src",Call(Var("fetchurl"),Attrs([Bind("md5",Str("7e935a42428d63a387b3c048be0f2756",[]),NoPos),Bind("url",Str("http://freedesktop.org/~xlibs/release/libXi-6.0.1.tar.bz2",[]),NoPos)])),NoPos)])),NoPos)
+Function(AttrsPat([Formal("stdenv",NoDefaultValue),Formal("fetchurl",NoDefaultValue)],Bool(False)),Call(Select(Var("stdenv"),"mkDerivation"),Attrs([Bind("name",Str("libXi-6.0.1",[]),NoPos),Bind("src",Call(Var("fetchurl"),Attrs([Bind("md5",Str("7e935a42428d63a387b3c048be0f2756",[]),NoPos),Bind("url",Str("http://freedesktop.org/~xlibs/release/libXi-6.0.1.tar.bz2",[]),NoPos)])),NoPos)])),NoPos)

tests/lang/parse-okay-subversion.exp

@@ -1 +1 @@
-Function(AttrsPat([Formal("localServer",DefaultValue(Var("false"))),Formal("httpServer",DefaultValue(Var("false"))),Formal("sslSupport",DefaultValue(Var("false"))),Formal("pythonBindings",DefaultValue(Var("false"))),Formal("javaSwigBindings",DefaultValue(Var("false"))),Formal("javahlBindings",DefaultValue(Var("false"))),Formal("stdenv",NoDefaultValue),Formal("fetchurl",NoDefaultValue),Formal("openssl",DefaultValue(Var("null"))),Formal("httpd",DefaultValue(Var("null"))),Formal("db4",DefaultValue(Var("null"))),Formal("expat",NoDefaultValue),Formal("swig",DefaultValue(Var("null"))),Formal("j2sdk",DefaultValue(Var("null")))]),Assert(OpNEq(Var("expat"),Var("null")),Assert(OpImpl(Var("localServer"),OpNEq(Var("db4"),Var("null"))),Assert(OpImpl(Var("httpServer"),OpAnd(OpNEq(Var("httpd"),Var("null")),OpEq(Select(Var("httpd"),"expat"),Var("expat")))),Assert(OpImpl(Var("sslSupport"),OpAnd(OpNEq(Var("openssl"),Var("null")),OpImpl(Var("httpServer"),OpEq(Select(Var("httpd"),"openssl"),Var("openssl"))))),Assert(OpImpl(Var("pythonBindings"),OpAnd(OpNEq(Var("swig"),Var("null")),Select(Var("swig"),"pythonSupport"))),Assert(OpImpl(Var("javaSwigBindings"),OpAnd(OpNEq(Var("swig"),Var("null")),Select(Var("swig"),"javaSupport"))),Assert(OpImpl(Var("javahlBindings"),OpNEq(Var("j2sdk"),Var("null"))),Call(Select(Var("stdenv"),"mkDerivation"),Attrs([Bind("builder",Path("/foo/bar"),NoPos),Bind("db4",If(Var("localServer"),Var("db4"),Var("null")),NoPos),Bind("expat",Var("expat"),NoPos),Bind("httpServer",Var("httpServer"),NoPos),Bind("httpd",If(Var("httpServer"),Var("httpd"),Var("null")),NoPos),Bind("j2sdk",If(Var("javaSwigBindings"),Select(Var("swig"),"j2sdk"),If(Var("javahlBindings"),Var("j2sdk"),Var("null"))),NoPos),Bind("javaSwigBindings",Var("javaSwigBindings"),NoPos),Bind("javahlBindings",Var("javahlBindings"),NoPos),Bind("localServer",Var("localServer"),NoPos),Bind("name",Str("subversion-1.1.1",[]),NoPos),Bind("openssl",If(Var("sslSupport"),Var("openssl"),Var("null")),NoPos),Bind("patches",If(Var("javahlBindings"),List([Path("/javahl.patch")]),List([])),NoPos),Bind("python",If(Var("pythonBindings"),Select(Var("swig"),"python"),Var("null")),NoPos),Bind("pythonBindings",Var("pythonBindings"),NoPos),Bind("src",Call(Var("fetchurl"),Attrs([Bind("md5",Str("a180c3fe91680389c210c99def54d9e0",[]),NoPos),Bind("url",Str("http://subversion.tigris.org/tarballs/subversion-1.1.1.tar.bz2",[]),NoPos)])),NoPos),Bind("sslSupport",Var("sslSupport"),NoPos),Bind("swig",If(OpOr(Var("pythonBindings"),Var("javaSwigBindings")),Var("swig"),Var("null")),NoPos)])),NoPos),NoPos),NoPos),NoPos),NoPos),NoPos),NoPos),NoPos)
+Function(AttrsPat([Formal("localServer",DefaultValue(Var("false"))),Formal("httpServer",DefaultValue(Var("false"))),Formal("sslSupport",DefaultValue(Var("false"))),Formal("pythonBindings",DefaultValue(Var("false"))),Formal("javaSwigBindings",DefaultValue(Var("false"))),Formal("javahlBindings",DefaultValue(Var("false"))),Formal("stdenv",NoDefaultValue),Formal("fetchurl",NoDefaultValue),Formal("openssl",DefaultValue(Var("null"))),Formal("httpd",DefaultValue(Var("null"))),Formal("db4",DefaultValue(Var("null"))),Formal("expat",NoDefaultValue),Formal("swig",DefaultValue(Var("null"))),Formal("j2sdk",DefaultValue(Var("null")))],Bool(False)),Assert(OpNEq(Var("expat"),Var("null")),Assert(OpImpl(Var("localServer"),OpNEq(Var("db4"),Var("null"))),Assert(OpImpl(Var("httpServer"),OpAnd(OpNEq(Var("httpd"),Var("null")),OpEq(Select(Var("httpd"),"expat"),Var("expat")))),Assert(OpImpl(Var("sslSupport"),OpAnd(OpNEq(Var("openssl"),Var("null")),OpImpl(Var("httpServer"),OpEq(Select(Var("httpd"),"openssl"),Var("openssl"))))),Assert(OpImpl(Var("pythonBindings"),OpAnd(OpNEq(Var("swig"),Var("null")),Select(Var("swig"),"pythonSupport"))),Assert(OpImpl(Var("javaSwigBindings"),OpAnd(OpNEq(Var("swig"),Var("null")),Select(Var("swig"),"javaSupport"))),Assert(OpImpl(Var("javahlBindings"),OpNEq(Var("j2sdk"),Var("null"))),Call(Select(Var("stdenv"),"mkDerivation"),Attrs([Bind("builder",Path("/foo/bar"),NoPos),Bind("db4",If(Var("localServer"),Var("db4"),Var("null")),NoPos),Bind("expat",Var("expat"),NoPos),Bind("httpServer",Var("httpServer"),NoPos),Bind("httpd",If(Var("httpServer"),Var("httpd"),Var("null")),NoPos),Bind("j2sdk",If(Var("javaSwigBindings"),Select(Var("swig"),"j2sdk"),If(Var("javahlBindings"),Var("j2sdk"),Var("null"))),NoPos),Bind("javaSwigBindings",Var("javaSwigBindings"),NoPos),Bind("javahlBindings",Var("javahlBindings"),NoPos),Bind("localServer",Var("localServer"),NoPos),Bind("name",Str("subversion-1.1.1",[]),NoPos),Bind("openssl",If(Var("sslSupport"),Var("openssl"),Var("null")),NoPos),Bind("patches",If(Var("javahlBindings"),List([Path("/javahl.patch")]),List([])),NoPos),Bind("python",If(Var("pythonBindings"),Select(Var("swig"),"python"),Var("null")),NoPos),Bind("pythonBindings",Var("pythonBindings"),NoPos),Bind("src",Call(Var("fetchurl"),Attrs([Bind("md5",Str("a180c3fe91680389c210c99def54d9e0",[]),NoPos),Bind("url",Str("http://subversion.tigris.org/tarballs/subversion-1.1.1.tar.bz2",[]),NoPos)])),NoPos),Bind("sslSupport",Var("sslSupport"),NoPos),Bind("swig",If(OpOr(Var("pythonBindings"),Var("javaSwigBindings")),Var("swig"),Var("null")),NoPos)])),NoPos),NoPos),NoPos),NoPos),NoPos),NoPos),NoPos),NoPos)