* Export the nix-env derivation name parsing and version comparison

logic through the `parseDrvName' and `compareVersions' primops.
  This will allow expressions to easily check whether some dependency
  is a specific needed version or falls in some version range.  See
  tests/lang/eval-okay-versions.nix for examples.

doc/manual/release-notes.xml

@@ -12,8 +12,14 @@
 
 <itemizedlist>
 
+  <listitem><para>TODO: Berkeley DB no longer needed.</para></listitem>
+
   <listitem><para><command>nix-store --dump-db / --load-db</command>.</para></listitem>
 
+  <listitem><para>New primops:
+  <varname>builtins.parseDrvName</varname> and
+  <varname>builtins.compareVersions</varname>.</para></listitem>
+
 </itemizedlist>
 
 </section>

src/libexpr/Makefile.am

@@ -2,11 +2,13 @@ pkglib_LTLIBRARIES = libexpr.la
 
 libexpr_la_SOURCES = \
  nixexpr.cc eval.cc primops.cc lexer-tab.cc parser-tab.cc \
- get-drvs.cc attr-path.cc expr-to-xml.cc common-opts.cc
+ get-drvs.cc attr-path.cc expr-to-xml.cc common-opts.cc \
+ names.cc
 
 pkginclude_HEADERS = \
  nixexpr.hh eval.hh parser.hh lexer-tab.hh parser-tab.hh \
- get-drvs.hh attr-path.hh expr-to-xml.hh common-opts.hh
+ get-drvs.hh attr-path.hh expr-to-xml.hh common-opts.hh \
+ names.hh
 
 libexpr_la_LIBADD = ../libutil/libutil.la ../libstore/libstore.la \
  ../boost/format/libformat.la

src/libexpr/names.cc

@@ -92,25 +92,6 @@ int compareVersions(const string & v1, const string & v2)
 }
 
 
-static void testCompareVersions()
-{
-#define TEST(v1, v2, n) assert( \
-    compareVersions(v1, v2) == n && compareVersions(v2, v1) == -n)
-    TEST("1.0", "2.3", -1);
-    TEST("2.1", "2.3", -1);
-    TEST("2.3", "2.3", 0);
-    TEST("2.5", "2.3", 1);
-    TEST("3.1", "2.3", 1);
-    TEST("2.3.1", "2.3", 1);
-    TEST("2.3.1", "2.3a", 1);
-    TEST("2.3pre1", "2.3", -1);
-    TEST("2.3pre3", "2.3pre12", -1);
-    TEST("2.3a", "2.3c", -1);
-    TEST("2.3pre1", "2.3c", -1);
-    TEST("2.3pre1", "2.3q", -1);
-}
-
-
 DrvNames drvNamesFromArgs(const Strings & opArgs)
 {
     DrvNames result;

src/libexpr/primops.cc

@@ -7,6 +7,7 @@
 #include "expr-to-xml.hh"
 #include "nixexpr-ast.hh"
 #include "parser.hh"
+#include "names.hh"
 
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -817,7 +818,7 @@ static Expr prim_removeAttrs(EvalState & state, const ATermVector & args)
 }
 
 
-/* Determine whether the argument is a list. */
+/* Determine whether the argument is an attribute set. */
 static Expr prim_isAttrs(EvalState & state, const ATermVector & args)
 {
     ATermList list;
@@ -950,23 +951,54 @@ static Expr prim_unsafeDiscardStringContext(EvalState & state, const ATermVector
     return makeStr(s, PathSet());
 }
 
+
 /* Expression serialization/deserialization */
 
-static Expr prim_ExprToString ( EvalState & state, const ATermVector & args)
+
+static Expr prim_exprToString(EvalState & state, const ATermVector & args)
 {
-	return makeStr ( atPrint ( evalExpr ( state, args [ 0 ] ) ) );
+    /* !!! this disregards context */
+    return makeStr(atPrint(evalExpr(state, args[0])));
 }
 
-static Expr prim_StringToExpr ( EvalState & state, const ATermVector & args)
+
+static Expr prim_stringToExpr(EvalState & state, const ATermVector & args)
 {
-	string s;
-	PathSet l;
-	if (! matchStr ( evalExpr ( state, args[0] ), s, l )) {
-		throw EvalError("__stringToExpr needs string argument!");
-	}
-	return ATreadFromString(s.c_str());
+    /* !!! this can introduce arbitrary garbage terms in the
+       evaluator! */;
+    string s;
+    PathSet l;
+    if (!matchStr(evalExpr(state, args[0]), s, l))
+        throw EvalError("stringToExpr needs string argument!");
+    return ATreadFromString(s.c_str());
 }
 
+
+/*************************************************************
+ * Versions
+ *************************************************************/
+
+
+static Expr prim_parseDrvName(EvalState & state, const ATermVector & args)
+{
+    string name = evalStringNoCtx(state, args[0]);
+    DrvName parsed(name);
+    ATermMap attrs(2);
+    attrs.set(toATerm("name"), makeAttrRHS(makeStr(parsed.name), makeNoPos()));
+    attrs.set(toATerm("version"), makeAttrRHS(makeStr(parsed.version), makeNoPos()));
+    return makeAttrs(attrs);
+}
+
+
+static Expr prim_compareVersions(EvalState & state, const ATermVector & args)
+{
+    string version1 = evalStringNoCtx(state, args[0]);
+    string version2 = evalStringNoCtx(state, args[1]);
+    int d = compareVersions(version1, version2);
+    return makeInt(d);
+}
+
+
 /*************************************************************
  * Primop registration
  *************************************************************/
@@ -994,8 +1026,8 @@ void EvalState::addPrimOps()
     addPrimOp("__trace", 2, prim_trace);
     
     // Expr <-> String
-    addPrimOp("__exprToString", 1, prim_ExprToString);
-    addPrimOp("__stringToExpr", 1, prim_StringToExpr);
+    addPrimOp("__exprToString", 1, prim_exprToString);
+    addPrimOp("__stringToExpr", 1, prim_stringToExpr);
 
     addPrimOp("relativise", 2, prim_relativise);
 
@@ -1040,6 +1072,9 @@ void EvalState::addPrimOps()
     addPrimOp("__stringLength", 1, prim_stringLength);
     addPrimOp("__unsafeDiscardStringContext", 1, prim_unsafeDiscardStringContext);
 
+    // Versions
+    addPrimOp("__parseDrvName", 1, prim_parseDrvName);
+    addPrimOp("__compareVersions", 2, prim_compareVersions);
 }
 
 

src/nix-env/Makefile.am

@@ -1,7 +1,6 @@
 bin_PROGRAMS = nix-env
 
-nix_env_SOURCES = nix-env.cc names.cc names.hh \
- profiles.cc profiles.hh help.txt
+nix_env_SOURCES = nix-env.cc profiles.cc profiles.hh help.txt
 nix_env_LDADD = ../libmain/libmain.la ../libexpr/libexpr.la \
  ../libstore/libstore.la ../libutil/libutil.la \
  ../boost/format/libformat.la ${bdb_lib} ${aterm_lib}

tests/lang/eval-okay-versions.exp

@@ -0,0 +1 @@
+Bool(True)

tests/lang/eval-okay-versions.nix

@@ -0,0 +1,40 @@
+let
+
+  name1 = "hello-1.0.2";
+  name2 = "hello";
+  name3 = "915resolution-0.5.2";
+  name4 = "xf86-video-i810-1.7.4";
+
+  eq = 0;
+  lt = builtins.sub 0 1;
+  gt = 1;
+
+  versionTest = v1: v2: expected:
+    let d1 = builtins.compareVersions v1 v2;
+        d2 = builtins.compareVersions v2 v1;
+    in d1 == builtins.sub 0 d2 && d1 == expected;
+
+  tests = [
+    ((builtins.parseDrvName name1).name == "hello")
+    ((builtins.parseDrvName name1).version == "1.0.2")
+    ((builtins.parseDrvName name2).name == "hello")
+    ((builtins.parseDrvName name2).version == "")
+    ((builtins.parseDrvName name3).name == "915resolution")
+    ((builtins.parseDrvName name3).version == "0.5.2")
+    ((builtins.parseDrvName name4).name == "xf86-video-i810")
+    ((builtins.parseDrvName name4).version == "1.7.4")
+    (versionTest "1.0" "2.3" lt)
+    (versionTest "2.1" "2.3" lt)
+    (versionTest "2.3" "2.3" eq)
+    (versionTest "2.5" "2.3" gt)
+    (versionTest "3.1" "2.3" gt)
+    (versionTest "2.3.1" "2.3" gt)
+    (versionTest "2.3.1" "2.3a" gt)
+    (versionTest "2.3pre1" "2.3" lt)
+    (versionTest "2.3pre3" "2.3pre12" lt)
+    (versionTest "2.3a" "2.3c" lt)
+    (versionTest "2.3pre1" "2.3c" lt)
+    (versionTest "2.3pre1" "2.3q" lt)
+  ];
+
+in (import ./lib.nix).and tests

tests/lang/lib.nix

@@ -10,6 +10,8 @@ rec {
   concat =
     fold (x: y: x + y) "";
 
+  and = fold (x: y: x && y) true;
+
   flatten = x:
     if isList x
     then fold (x: y: (flatten x) ++ y) [] x