From 45a28ed36f769c1db57b805d95967a997ccab3e2 Mon Sep 17 00:00:00 2001
From: regnat <rg@regnat.ovh>
Date: Thu, 3 Jun 2021 10:50:32 +0200
Subject: [PATCH] Extract a Value method to get the eval cache

---
 src/libexpr/eval.cc        | 40 ++++++++++++++++++++++++--------------
 src/libexpr/value-cache.hh |  2 +-
 src/libexpr/value.hh       |  4 ++++
 3 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index e94e64346..debdf4e42 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1,4 +1,5 @@
 #include "eval.hh"
+#include "value-cache.hh"
 #include "hash.hh"
 #include "util.hh"
 #include "store-api.hh"
@@ -1190,23 +1191,22 @@ bool EvalState::getAttrField(Value & attrs, const std::vector<Symbol> & selector
     Pos * pos2 = 0;
 
     forceValue(attrs, pos);
-    if (attrs.type() == nAttrs) {
-        auto eval_cache = attrs.attrs->eval_cache;
-        auto [ cacheResult, resultingCursor ] = eval_cache.getValue(*this, selector, dest);
-        updateCacheStats(cacheResult);
-        switch (cacheResult.returnCode) {
-            case ValueCache::CacheHit:
-                if (cacheResult.lastQueriedSymbolIfMissing)
-                    return false;
-                return true;
-            case ValueCache::CacheMiss: // FIXME: Handle properly
-            case ValueCache::Forward: // FIXME: Handle properly
-            case ValueCache::NoCacheKey:
-            case ValueCache::UnCacheable:
-                ;
-        }
+    auto eval_cache = attrs.getEvalCache();
+    auto [ cacheResult, resultingCursor ] = eval_cache.getValue(*this, selector, dest);
+    updateCacheStats(cacheResult);
+    switch (cacheResult.returnCode) {
+        case ValueCache::CacheHit:
+            if (cacheResult.lastQueriedSymbolIfMissing)
+                return false;
+            return true;
+        case ValueCache::CacheMiss: // FIXME: Handle properly
+        case ValueCache::Forward: // FIXME: Handle properly
+        case ValueCache::NoCacheKey:
+        case ValueCache::UnCacheable:
+            ;
     }
 
+
     Value * vAttrs = &attrs;
     try {
         for (auto & name : selector) {
@@ -1802,6 +1802,16 @@ std::vector<std::pair<Path, std::string>> Value::getContext()
     return res;
 }
 
+ValueCache & Value::getEvalCache()
+{
+    if (internalType == tAttrs) {
+        return attrs->eval_cache;
+    } else {
+        return ValueCache::empty;
+    }
+}
+
+ValueCache ValueCache::empty = ValueCache(nullptr);
 
 string EvalState::forceString(Value & v, PathSet & context, const Pos & pos)
 {
diff --git a/src/libexpr/value-cache.hh b/src/libexpr/value-cache.hh
index e36e03ad8..177f97ad2 100644
--- a/src/libexpr/value-cache.hh
+++ b/src/libexpr/value-cache.hh
@@ -13,7 +13,7 @@ public:
 
     ValueCache(tree_cache::Cursor::Ref rawCache) : rawCache(rawCache) {}
 
-    const static ValueCache empty;
+    static ValueCache empty;
 
     bool isEmpty () { return rawCache == nullptr; }
 
diff --git a/src/libexpr/value.hh b/src/libexpr/value.hh
index a1f131f9e..740a19f0c 100644
--- a/src/libexpr/value.hh
+++ b/src/libexpr/value.hh
@@ -57,6 +57,8 @@ class EvalState;
 class XMLWriter;
 class JSONPlaceholder;
 
+class ValueCache;
+
 
 typedef int64_t NixInt;
 typedef double NixFloat;
@@ -349,6 +351,8 @@ public:
     bool isTrivial() const;
 
     std::vector<std::pair<Path, std::string>> getContext();
+
+    ValueCache & getEvalCache();
 };