* 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.

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\-\_\.\!\~\*\'\(\)\/]
 
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

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);
+}

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 */

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;
         }
     }

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);
     }
-#endif
 
+    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);
+        }
+    }
+
+#if 0
     Paths sucs;
     nixDB.enumTable(txn, dbSuccessors, sucs);
 
@@ -395,6 +411,7 @@ void verifyStore()
             nixDB.setStrings(txn, dbSuccessorsRev, sucPath, revs);
         }
     }
+#endif
 
     txn.commit();
 }

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);
 

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);
 }