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.

4 files changed, 32 insertions, 31 deletions

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 6ac07eed6..50f36ce4e 100644
--- a/src/libexpr/eval.cc
+++ b/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);
-        try {
-            eval(e, v);
-        } catch (Error & e) {
-            addErrorPrefix(e, "while evaluating the file `%1%':\n", path);
-            throw;
-        }
-        fileEvalCache[path] = v;
-    } else
+    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", path2);
+        throw;
+    }
+    fileEvalCache[path2] = v;
+    //if (path != path2) fileEvalCache[path2] = v;
 }
 
 
 void EvalState::resetFileCache()
 {
     fileEvalCache.clear();
-    parseTrees.clear();
 }
 
 
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 98ac0bdb4..29c8341df 100644
--- a/src/libexpr/eval.hh
+++ b/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);
+
+
 }
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 623ac641c..c63043c4d 100644
--- a/src/libexpr/parser.y
+++ b/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);
 }
 
 
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index bcaa51dd6..a216fa7ab 100644
--- a/src/libexpr/primops.cc
+++ b/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