* Maintain integrity of the substitute and successor mappings when

  deleting a path in the store.
* Allow absolute paths in Nix expressions.
* Get nix-prefetch-url to work again.
* Various other fixes.

15 files changed, 151 insertions, 198 deletions

diff --git a/corepkgs/fetchurl/Makefile.am b/corepkgs/fetchurl/Makefile.am
index 0c8f0c9399..270bf01424 100644
--- a/corepkgs/fetchurl/Makefile.am
+++ b/corepkgs/fetchurl/Makefile.am
@@ -1,10 +1,11 @@
-all-local: fetchurl.sh
+all-local: builder.sh
 
 install-exec-local:
-	$(INSTALL) -d $(datadir)/fix/fetchurl
-	$(INSTALL_DATA) fetchurl.fix $(datadir)/fix/fetchurl
-	$(INSTALL_PROGRAM) fetchurl.sh $(datadir)/fix/fetchurl
+	$(INSTALL) -d $(datadir)/nix/corepkgs
+	$(INSTALL) -d $(datadir)/nix/corepkgs/fetchurl
+	$(INSTALL_DATA) default.nix $(datadir)/nix/corepkgs/fetchurl
+	$(INSTALL_PROGRAM) builder.sh $(datadir)/nix/corepkgs/fetchurl
 
 include ../../substitute.mk
 
-EXTRA_DIST = fetchurl.fix fetchurl.sh.in
+EXTRA_DIST = default.nix builder.sh.in
diff --git a/corepkgs/fetchurl/fetchurl.sh.in b/corepkgs/fetchurl/builder.sh.in
index a6cc699302..a6cc699302 100644
--- a/corepkgs/fetchurl/fetchurl.sh.in
+++ b/corepkgs/fetchurl/builder.sh.in
diff --git a/corepkgs/fetchurl/default.nix b/corepkgs/fetchurl/default.nix
new file mode 100644
index 0000000000..663bba4a38
--- /dev/null
+++ b/corepkgs/fetchurl/default.nix
@@ -0,0 +1,8 @@
+{system, url, md5}: derivation {
+  name = baseNameOf (toString url);
+  system = system;
+  builder = ./builder.sh;
+  url = url;
+  md5 = md5;
+  id = md5;
+}
diff --git a/corepkgs/fetchurl/fetchurl.fix b/corepkgs/fetchurl/fetchurl.fix
deleted file mode 100644
index 0221b612cf..0000000000
--- a/corepkgs/fetchurl/fetchurl.fix
+++ /dev/null
@@ -1,10 +0,0 @@
-Function(["url", "md5"],
-  Package(
-    [ ("build", Relative("fetchurl/fetchurl.sh"))
-    , ("url", Var("url"))
-    , ("md5", Var("md5"))
-    , ("name", BaseName(Var("url")))
-    , ("id", Var("md5"))
-    ]
-  )
-)
diff --git a/scripts/Makefile.am b/scripts/Makefile.am
index 4a1be7f8f0..35bb926af6 100644
--- a/scripts/Makefile.am
+++ b/scripts/Makefile.am
@@ -1,4 +1,4 @@
-bin_SCRIPTS = nix-switch nix-collect-garbage \
+bin_SCRIPTS = nix-collect-garbage \
  nix-pull nix-push nix-prefetch-url
 
 noinst_SCRIPTS = nix-profile.sh
diff --git a/scripts/nix-prefetch-url.in b/scripts/nix-prefetch-url.in
index 332290d40a..0873f5a8d7 100644
--- a/scripts/nix-prefetch-url.in
+++ b/scripts/nix-prefetch-url.in
@@ -22,27 +22,29 @@ print "file has hash $hash\n";
 my $out2 = "@prefix@/store/nix-prefetch-url-$hash";
 rename $out, $out2;
 
-# Create a Fix expression.
-my $fixexpr = 
-    "App(IncludeFix(\"fetchurl/fetchurl.fix\"), " .
-    "[(\"url\", \"$url\"), (\"md5\", \"$hash\")])";
+# Create a Nix expression.
+my $nixexpr =
+    "(import @datadir@/nix/corepkgs/fetchurl) " .
+    "{url = $url; md5 = \"$hash\"; system = \"@host@\"}";
+
+print "expr: $nixexpr\n";
 
 # Instantiate a Nix expression.
-print STDERR "running fix...\n";
-my $pid = open2(\*READ, \*WRITE, "fix -") or die "cannot run fix";
+print STDERR "instantiating Nix expression...\n";
+my $pid = open2(\*READ, \*WRITE, "nix-instantiate -") or die "cannot run nix-instantiate";
 
-print WRITE $fixexpr;
+print WRITE $nixexpr;
 close WRITE;
 
-my $id = <READ>;
-chomp $id;
+my $drvpath = <READ>;
+chomp $drvpath;
 
 waitpid $pid, 0;
-$? == 0 or die "fix failed";
+$? == 0 or die "nix-instantiate failed";
 
 # Run Nix.
-print STDERR "running nix...\n";
-system "nix --install $id > /dev/null";
-$? == 0 or die "`nix --install' failed";
+print STDERR "realising store expression $drvpath...\n";
+system "nix-store --realise $drvpath > /dev/null";
+$? == 0 or die "realisation failed";
 
 unlink $out2;
diff --git a/scripts/nix-switch.in b/scripts/nix-switch.in
deleted file mode 100755
index 9fcb598e30..0000000000
--- a/scripts/nix-switch.in
+++ /dev/null
@@ -1,86 +0,0 @@
-#! /usr/bin/perl -w
-
-use strict;
-
-my $keep = 0;
-my $sourceroot = 1;
-my $name = "current";
-my $srcid;
-
-my $argnr = 0;
-while ($argnr < scalar @ARGV) {
-    my $arg = $ARGV[$argnr++];
-    if ($arg eq "--keep") { $keep = 1; }
-    elsif ($arg eq "--no-source") { $sourceroot = 0; }
-    elsif ($arg eq "--name") { $name = $ARGV[$argnr++]; }
-    elsif ($arg =~ /^\//) { $srcid = $arg; }
-    else { die "unknown argument `$arg'" };
-}
-
-my $linkdir = "@localstatedir@/nix/links";
-
-# Build the specified package, and all its dependencies.
-my $nfid = `nix --install $srcid`;
-if ($?) { die "`nix --install' failed"; }
-chomp $nfid;
-die unless $nfid =~ /^\//;
-
-my $pkgdir = `nix --query --list $nfid`;
-if ($?) { die "`nix --query --list' failed"; }
-chomp $pkgdir;
-
-# Figure out a generation number.
-opendir(DIR, $linkdir);
-my $nr = 0;
-foreach my $n (sort(readdir(DIR))) {
-    next if (!($n =~ /^\d+$/));
-    $nr = $n + 1 if ($n >= $nr);
-}
-closedir(DIR);
-
-my $link = "$linkdir/$nr";
-
-# Create a symlink from $link to $pkgdir.
-symlink($pkgdir, $link) or die "cannot create $link: $!";
-
-# Store the id of the normal form.  This is useful for garbage
-# collection and the like.
-my $idfile = "$linkdir/$nr.id";
-open ID, "> $idfile" or die "cannot create $idfile";
-print ID "$nfid\n";
-close ID;
-
-# Optionally store the source id.
-if ($sourceroot) {
-    $idfile = "$linkdir/$nr-src.id";
-    open ID, "> $idfile" or die "cannot create $idfile";
-    print ID "$srcid\n";
-    close ID;
-}
-
-my $current = "$linkdir/$name";
-
-# Read the current generation so that we can delete it (if --keep
-# wasn't specified).
-my $oldlink = readlink($current);
-
-# Make $link the current generation by pointing $linkdir/current to
-# it.  The rename() system call is supposed to be essentially atomic
-# on Unix.  That is, if we have links `current -> X' and `new_current
-# -> Y', and we rename new_current to current, a process accessing
-# current will see X or Y, but never a file-not-found or other error
-# condition.  This is sufficient to atomically switch the current link
-# tree.
-
-print "switching $current to $link\n";
-
-my $tmplink = "$linkdir/.new_$name";
-symlink($link, $tmplink) or die "cannot create $tmplink";
-rename($tmplink, $current) or die "cannot rename $tmplink";
-
-if (!$keep && defined $oldlink) {
-    print "deleting old $oldlink\n";
-    unlink($oldlink) == 1 or print "cannot delete $oldlink\n";
-    unlink("$oldlink.id") == 1 or print "cannot delete $oldlink.id\n";
-    unlink("$oldlink-src.id");
-}
diff --git a/src/libexpr/nix.sdf b/src/libexpr/nix.sdf
index 615bdb9747..b6bb23ebd4 100644
--- a/src/libexpr/nix.sdf
+++ b/src/libexpr/nix.sdf
@@ -104,6 +104,7 @@ exports
     "\"" ~[\n\"]* "\"" -> Str
 
     PathComp ("/" PathComp)+ -> Path
+    ("/" PathComp)+ -> Path
     [a-zA-Z0-9\.\_\-\+]+ -> PathComp
 
     "true" -> Bool
@@ -184,7 +185,7 @@ exports
     [0-9] -> Udigit
 
   lexical restrictions
-    Uri -/- [a-zA-Z0-9\-\_\.\!\~\*\'\(\)]
+    Uri -/- [a-zA-Z0-9\-\_\.\!\~\*\'\(\)\/]
 
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
diff --git a/src/libexpr/parser.cc b/src/libexpr/parser.cc
index e3c863a558..aecfa43487 100644
--- a/src/libexpr/parser.cc
+++ b/src/libexpr/parser.cc
@@ -66,23 +66,9 @@ struct Cleanup : TermFun
 };
 
 
-Expr parseExprFromFile(Path path)
+static Expr parse(const char * text, const string & location,
+    const Path & basePath)
 {
-    assert(path[0] == '/');
-
-#if 0
-    /* Perhaps this is already an imploded parse tree? */
-    Expr e = ATreadFromNamedFile(path.c_str());
-    if (e) return e;
-#endif
-
-    /* If `path' refers to a directory, append `/default.nix'. */
-    struct stat st;
-    if (stat(path.c_str(), &st))
-        throw SysError(format("getting status of `%1%'") % path);
-    if (S_ISDIR(st.st_mode))
-        path = canonPath(path + "/default.nix");
-
     /* Initialise the SDF libraries. */
     static bool initialised = false;
     static ATerm parseTable = 0;
@@ -113,26 +99,13 @@ Expr parseExprFromFile(Path path)
         initialised = true;
     }
 
-    /* Read the input file.  We can't use SGparseFile() because it's
-       broken, so we read the input ourselves and call
-       SGparseString(). */
-    AutoCloseFD fd = open(path.c_str(), O_RDONLY);
-    if (fd == -1) throw SysError(format("opening `%1%'") % path);
-
-    if (fstat(fd, &st) == -1)
-        throw SysError(format("statting `%1%'") % path);
-
-    char text[st.st_size + 1];
-    readFull(fd, (unsigned char *) text, st.st_size);
-    text[st.st_size] = 0;
-
     /* Parse it. */
-    ATerm result = SGparseString(lang, "Expr", text);
+    ATerm result = SGparseString(lang, "Expr", (char *) text);
     if (!result)
-        throw SysError(format("parse failed in `%1%'") % path);
+        throw SysError(format("parse failed in `%1%'") % location);
     if (SGisParseError(result))
         throw Error(format("parse error in `%1%': %2%")
-            % path % result);
+            % location % result);
 
     /* Implode it. */
     PT_ParseTree tree = PT_makeParseTreeFromTerm(result);
@@ -155,10 +128,50 @@ Expr parseExprFromFile(Path path)
         throw Error(format("cannot implode parse tree"));
 
     printMsg(lvlVomit, format("imploded parse tree of `%1%': %2%")
-        % path % imploded);
+        % location % imploded);
 
     /* Finally, clean it up. */
     Cleanup cleanup;
-    cleanup.basePath = dirOf(path);
+    cleanup.basePath = basePath;
     return bottomupRewrite(cleanup, imploded);
 }
+
+
+Expr parseExprFromFile(Path path)
+{
+    assert(path[0] == '/');
+
+#if 0
+    /* Perhaps this is already an imploded parse tree? */
+    Expr e = ATreadFromNamedFile(path.c_str());
+    if (e) return e;
+#endif
+
+    /* If `path' refers to a directory, append `/default.nix'. */
+    struct stat st;
+    if (stat(path.c_str(), &st))
+        throw SysError(format("getting status of `%1%'") % path);
+    if (S_ISDIR(st.st_mode))
+        path = canonPath(path + "/default.nix");
+
+    /* Read the input file.  We can't use SGparseFile() because it's
+       broken, so we read the input ourselves and call
+       SGparseString(). */
+    AutoCloseFD fd = open(path.c_str(), O_RDONLY);
+    if (fd == -1) throw SysError(format("opening `%1%'") % path);
+
+    if (fstat(fd, &st) == -1)
+        throw SysError(format("statting `%1%'") % path);
+
+    char text[st.st_size + 1];
+    readFull(fd, (unsigned char *) text, st.st_size);
+    text[st.st_size] = 0;
+
+    return parse(text, path, dirOf(path));
+}
+
+
+Expr parseExprFromString(const string & s, const Path & basePath)
+{
+    return parse(s.c_str(), "(string)", basePath);
+}
diff --git a/src/libexpr/parser.hh b/src/libexpr/parser.hh
index 5983ec5629..461dae08cd 100644
--- a/src/libexpr/parser.hh
+++ b/src/libexpr/parser.hh
@@ -4,7 +4,13 @@
 #include "nixexpr.hh"
 
 
+/* Parse a Nix expression from the specified file.  If `path' refers
+   to a directory, the "/default.nix" is appended. */
 Expr parseExprFromFile(Path path);
 
+/* Parse a Nix expression from the specified string. */
+Expr parseExprFromString(const string & s,
+    const Path & basePath);
+
 
 #endif /* !__PARSER_H */
diff --git a/src/libstore/normalise.cc b/src/libstore/normalise.cc
index db85c3b5b8..7ef45e2923 100644
--- a/src/libstore/normalise.cc
+++ b/src/libstore/normalise.cc
@@ -82,6 +82,7 @@ Path normaliseStoreExpr(const Path & _nePath, PathSet pending)
             debug(format("skipping build of expression `%1%', someone beat us to it")
 		  % (string) nePath);
             if (ne.type != StoreExpr::neClosure) abort();
+            outputLocks.setDeletion(true);
             return nePath2;
         }
     }
diff --git a/src/libstore/store.cc b/src/libstore/store.cc
index caaa293a6f..4c6b8bbecb 100644
--- a/src/libstore/store.cc
+++ b/src/libstore/store.cc
@@ -243,16 +243,33 @@ bool isValidPath(const Path & path)
 }
 
 
-void unregisterValidPath(const Path & _path)
+static void invalidatePath(const Path & path, Transaction & txn)
 {
-    Path path(canonPath(_path));
-    Transaction txn(nixDB);
-
     debug(format("unregistering path `%1%'") % path);
 
     nixDB.delPair(txn, dbValidPaths, path);
 
-    txn.commit();
+    /* Remove any successor mappings to this path (but not *from*
+       it). */
+    Paths revs;
+    nixDB.queryStrings(txn, dbSuccessorsRev, path, revs);
+    for (Paths::iterator i = revs.begin(); i != revs.end(); ++i)
+        nixDB.delPair(txn, dbSuccessors, *i);
+    nixDB.delPair(txn, dbSuccessorsRev, path);
+
+    /* Remove any substitute mappings to this path. */
+    revs.clear();
+    nixDB.queryStrings(txn, dbSubstitutesRev, path, revs);
+    for (Paths::iterator i = revs.begin(); i != revs.end(); ++i) {
+        Paths subs;
+        nixDB.queryStrings(txn, dbSubstitutes, *i, subs);
+        remove(subs.begin(), subs.end(), path);
+        if (subs.size() > 0)
+            nixDB.setStrings(txn, dbSubstitutes, *i, subs);
+        else
+            nixDB.delPair(txn, dbSubstitutes, *i);
+    }
+    nixDB.delPair(txn, dbSubstitutesRev, path);
 }
 
 
@@ -289,6 +306,8 @@ Path addToStore(const Path & _srcPath)
             registerValidPath(txn, dstPath);
             txn.commit();
         }
+
+        outputLock.setDeletion(true);
     }
 
     return dstPath;
@@ -310,6 +329,8 @@ void addTextToStore(const Path & dstPath, const string & s)
             registerValidPath(txn, dstPath);
             txn.commit();
         }
+
+        outputLock.setDeletion(true);
     }
 }
 
@@ -321,7 +342,9 @@ void deleteFromStore(const Path & _path)
     if (!isInPrefix(path, nixStore))
         throw Error(format("path `%1%' is not in the store") % path);
 
-    unregisterValidPath(path);
+    Transaction txn(nixDB);
+    invalidatePath(path, txn);
+    txn.commit();
 
     deletePath(path);
 }
@@ -332,50 +355,43 @@ void verifyStore()
     Transaction txn(nixDB);
 
     Paths paths;
+    PathSet validPaths;
     nixDB.enumTable(txn, dbValidPaths, paths);
 
-    for (Paths::iterator i = paths.begin();
-         i != paths.end(); i++)
+    for (Paths::iterator i = paths.begin(); i != paths.end(); ++i)
     {
         Path path = *i;
         if (!pathExists(path)) {
             debug(format("path `%1%' disappeared") % path);
-            nixDB.delPair(txn, dbValidPaths, path);
-            nixDB.delPair(txn, dbSuccessorsRev, path);
-            nixDB.delPair(txn, dbSubstitutesRev, path);
-        }
+            invalidatePath(path, txn);
+        } else
+            validPaths.insert(path);
     }
 
-#if 0    
-    Strings subs;
-    nixDB.enumTable(txn, dbSubstitutes, subs);
-
-    for (Strings::iterator i = subs.begin();
-         i != subs.end(); i++)
-    {
-        FSId srcId = parseHash(*i);
-
-        Strings subIds;
-        nixDB.queryStrings(txn, dbSubstitutes, srcId, subIds);
-
-        for (Strings::iterator j = subIds.begin();     
-             j != subIds.end(); )
+    Paths sucs;
+    nixDB.enumTable(txn, dbSuccessors, sucs);
+    for (Paths::iterator i = sucs.begin(); i != sucs.end(); ++i) {
+        /* Note that *i itself does not have to be valid, just its
+           successor. */
+        Path sucPath;
+        if (nixDB.queryString(txn, dbSuccessors, *i, sucPath) &&
+            validPaths.find(sucPath) == validPaths.end())
         {
-            FSId subId = parseHash(*j);
-            
-            Strings subPaths;
-            nixDB.queryStrings(txn, dbId2Paths, subId, subPaths);
-            if (subPaths.size() == 0) {
-                debug(format("erasing substitute %1% for %2%") 
-                    % (string) subId % (string) srcId);
-                j = subIds.erase(j);
-            } else j++;
+            debug(format("found successor mapping to non-existent path `%1%'") % sucPath);
+            nixDB.delPair(txn, dbSuccessors, *i);
         }
+    }
 
-        nixDB.setStrings(txn, dbSubstitutes, srcId, subIds);
+    Paths rsucs;
+    nixDB.enumTable(txn, dbSuccessorsRev, rsucs);
+    for (Paths::iterator i = rsucs.begin(); i != rsucs.end(); ++i) {
+        if (validPaths.find(*i) == validPaths.end()) {
+            debug(format("found reverse successor mapping for non-existent path `%1%'") % *i);
+            nixDB.delPair(txn, dbSuccessorsRev, *i);
+        }
     }
-#endif
 
+#if 0
     Paths sucs;
     nixDB.enumTable(txn, dbSuccessors, sucs);
 
@@ -395,6 +411,7 @@ void verifyStore()
             nixDB.setStrings(txn, dbSuccessorsRev, sucPath, revs);
         }
     }
+#endif
 
     txn.commit();
 }
diff --git a/src/libstore/store.hh b/src/libstore/store.hh
index dab3d603f8..143cad8dbe 100644
--- a/src/libstore/store.hh
+++ b/src/libstore/store.hh
@@ -48,9 +48,6 @@ Paths querySubstitutes(const Path & srcPath);
 /* Register the validity of a path. */
 void registerValidPath(const Transaction & txn, const Path & path);
 
-/* Unregister the validity of a path. */
-void unregisterValidPath(const Path & path);
-
 /* Checks whether a path is valid. */ 
 bool isValidPath(const Path & path);
 
diff --git a/src/nix-instantiate/main.cc b/src/nix-instantiate/main.cc
index aa6883ff84..f63789fc4b 100644
--- a/src/nix-instantiate/main.cc
+++ b/src/nix-instantiate/main.cc
@@ -5,6 +5,7 @@
 #include "normalise.hh"
 #include "shared.hh"
 #include "eval.hh"
+#include "parser.hh"
 
 
 #if 0
@@ -29,9 +30,9 @@ static Path searchPath(const Paths & searchDirs, const Path & relPath)
 static Expr evalStdin(EvalState & state)
 {
     startNest(nest, lvlTalkative, format("evaluating standard input"));
-    Expr e = ATreadFromFile(stdin);
-    if (!e) 
-        throw Error(format("unable to read a term from stdin"));
+    string s, s2;
+    while (getline(cin, s2)) s += s2 + "\n";
+    Expr e = parseExprFromString(s, absPath("."));
     return evalExpr(state, e);
 }
 
diff --git a/substitute.mk b/substitute.mk
index 8527cf6fd1..c575dc0ff0 100644
--- a/substitute.mk
+++ b/substitute.mk
@@ -1,9 +1,11 @@
 %: %.in Makefile
 	sed \
-	 -e s^@prefix\@^$(prefix)^g \
-	 -e s^@bindir\@^$(bindir)^g \
-	 -e s^@sysconfdir\@^$(sysconfdir)^g \
-	 -e s^@localstatedir\@^$(localstatedir)^g \
-	 -e s^@wget\@^$(wget)^g \
+	 -e "s^@prefix\@^$(prefix)^g" \
+	 -e "s^@bindir\@^$(bindir)^g" \
+	 -e "s^@sysconfdir\@^$(sysconfdir)^g" \
+	 -e "s^@localstatedir\@^$(localstatedir)^g" \
+	 -e "s^@datadir\@^$(datadir)^g" \
+	 -e "s^@host\@^$(host)^g" \
+	 -e "s^@wget\@^$(wget)^g" \
 	 < $< > $@ || rm $@
 	chmod +x $@