Get rid of the parse tree cache

Since we already cache files in normal form (fileEvalCache), caching
parse trees is redundant.

Note that getting rid of this cache doesn't actually save much memory
at the moment, because parse trees are currently not freed / GC'ed.

src/libexpr/eval.cc

@@ -440,26 +440,30 @@ Value * ExprPath::maybeThunk(EvalState & state, Env & env)
 
 void EvalState::evalFile(const Path & path, Value & v)
 {
-    FileEvalCache::iterator i = fileEvalCache.find(path);
-    if (i == fileEvalCache.end()) {
-        startNest(nest, lvlTalkative, format("evaluating file `%1%'") % path);
-        Expr * e = parseExprFromFile(path);
+    Path path2 = resolveExprPath(path);
+
+    FileEvalCache::iterator i = fileEvalCache.find(path2);
+    if (i != fileEvalCache.end()) {
+        v = i->second;
+        return;
+    }
+
+    startNest(nest, lvlTalkative, format("evaluating file `%1%'") % path2);
+    Expr * e = parseExprFromFile(path2);
     try {
         eval(e, v);
     } catch (Error & e) {
-            addErrorPrefix(e, "while evaluating the file `%1%':\n", path);
+        addErrorPrefix(e, "while evaluating the file `%1%':\n", path2);
         throw;
     }
-        fileEvalCache[path] = v;
-    } else
-        v = i->second;
+    fileEvalCache[path2] = v;
+    //if (path != path2) fileEvalCache[path2] = v;
 }
 
 
 void EvalState::resetFileCache()
 {
     fileEvalCache.clear();
-    parseTrees.clear();
 }
 
 

src/libexpr/eval.hh

@@ -103,9 +103,6 @@ public:
 private:
     SrcToStore srcToStore;
 
-    /* A cache from path names to parse trees. */
-    std::map<Path, Expr *> parseTrees;
-
     /* A cache from path names to values. */
 #if HAVE_BOEHMGC
     typedef std::map<Path, Value, std::less<Path>, gc_allocator<std::pair<const Path, Value> > > FileEvalCache;
@@ -125,9 +122,8 @@ public:
 
     void addToSearchPath(const string & s);
 
-    /* Parse a Nix expression from the specified file.  If `path'
-       refers to a directory, then "/default.nix" is appended. */
-    Expr * parseExprFromFile(Path path);
+    /* Parse a Nix expression from the specified file. */
+    Expr * parseExprFromFile(const Path & path);
 
     /* Parse a Nix expression from the specified string. */
     Expr * parseExprFromString(const string & s, const Path & basePath, StaticEnv & staticEnv);
@@ -278,4 +274,8 @@ private:
 string showType(const Value & v);
 
 
+/* If `path' refers to a directory, then append "/default.nix". */
+Path resolveExprPath(Path path);
+
+
 }

src/libexpr/parser.y

@@ -505,7 +505,7 @@ Expr * EvalState::parse(const char * text,
 }
 
 
-Expr * EvalState::parseExprFromFile(Path path)
+Path resolveExprPath(Path path)
 {
     assert(path[0] == '/');
 
@@ -523,15 +523,13 @@ Expr * EvalState::parseExprFromFile(Path path)
     if (S_ISDIR(st.st_mode))
         path = canonPath(path + "/default.nix");
 
-    /* Read and parse the input file, unless it's already in the parse
-       tree cache. */
-    Expr * e = parseTrees[path];
-    if (!e) {
-        e = parse(readFile(path).c_str(), path, dirOf(path), staticBaseEnv);
-        parseTrees[path] = e;
+    return path;
 }
 
-    return e;
+
+Expr * EvalState::parseExprFromFile(const Path & path)
+{
+    return parse(readFile(path).c_str(), path, dirOf(path), staticBaseEnv);
 }
 
 

src/libexpr/primops.cc

@@ -82,8 +82,7 @@ static void prim_import(EvalState & state, Value * * args, Value & v)
         }
         w.attrs->sort();
         Value fun;
-        state.mkThunk_(fun,
-            state.parseExprFromFile(state.findFile("nix/imported-drv-to-derivation.nix")));
+        state.evalFile(state.findFile("nix/imported-drv-to-derivation.nix"), fun);
         state.forceFunction(fun);
         mkApp(v, fun, w);
         state.forceAttrs(v);
@@ -1263,7 +1262,7 @@ void EvalState::createBaseEnv()
 
     /* Add a wrapper around the derivation primop that computes the
        `drvPath' and `outPath' attributes lazily. */
-    mkThunk_(v, parseExprFromFile(findFile("nix/derivation.nix")));
+    evalFile(findFile("nix/derivation.nix"), v);
     addConstant("derivation", v);
 
     /* Now that we've added all primops, sort the `builtins' attribute

src/nix-env/nix-env.cc

@@ -131,7 +131,7 @@ static void getAllExprs(EvalState & state,
             if (hasSuffix(attrName, ".nix"))
                 attrName = string(attrName, 0, attrName.size() - 4);
             attrs.attrs[state.symbols.create(attrName)] =
-                ExprAttrs::AttrDef(state.parseExprFromFile(absPath(path2)), noPos);
+                ExprAttrs::AttrDef(state.parseExprFromFile(resolveExprPath(absPath(path2))), noPos);
         }
         else
             /* `path2' is a directory (with no default.nix in it);
@@ -143,7 +143,7 @@ static void getAllExprs(EvalState & state,
 
 static Expr * loadSourceExpr(EvalState & state, const Path & path)
 {
-    if (isNixExpr(path)) return state.parseExprFromFile(absPath(path));
+    if (isNixExpr(path)) return state.parseExprFromFile(resolveExprPath(absPath(path)));
 
     /* The path is a directory.  Put the Nix expressions in the
        directory in an attribute set, with the file name of each

src/nix-instantiate/nix-instantiate.cc

@@ -160,7 +160,7 @@ void run(Strings args)
         files.push_back("./default.nix");
 
     foreach (Strings::iterator, i, files) {
-        Expr * e = state.parseExprFromFile(lookupFileArg(state, *i));
+        Expr * e = state.parseExprFromFile(resolveExprPath(lookupFileArg(state, *i)));
         processExpr(state, attrPaths, parseOnly, strict, autoArgs,
             evalOnly, xmlOutput, xmlOutputSourceLocation, e);
     }