From 8d2be51d19830754db260e91521e58a947719574 Mon Sep 17 00:00:00 2001
From: regnat <rg@regnat.ovh>
Date: Wed, 9 Jun 2021 16:28:41 +0200
Subject: [PATCH] Cache the evaluation errors
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Doesn’t seem to make much of a difference on `nix search`, but we’ll
need it at some point
---
 src/libexpr/eval.cc | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index cc562328a..48752a925 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1261,7 +1261,12 @@ bool EvalState::getAttrField(Value & attrs, const std::vector<Symbol> & selector
             }
             vAttrs = j->value;
             pos2 = j->pos;
-            forceValue(*vAttrs, pos2 != NULL ? *pos2 : pos );
+            try {
+                forceValue(*vAttrs, pos2 != NULL ? *pos2 : pos );
+            } catch (EvalError & e) {
+                resultingCursor.addFailedChild(name, e);
+                throw;
+            }
             if (cacheResult.returnCode == ValueCache::CacheMiss) {
                 resultingCursor = resultingCursor.addChild(name, *vAttrs);
                 vAttrs->setEvalCache(resultingCursor);
@@ -1984,6 +1989,13 @@ ValueCache ValueCache::addChild(const Symbol& name, Value& value)
     return ret;
 }
 
+
+ValueCache ValueCache::addFailedChild(const Symbol& name, const Error & error)
+{
+    if (!rawCache) return ValueCache::empty;
+    return ValueCache(rawCache->addChild(name, tree_cache::failed_t{ .error = error.msg() }));
+}
+
 void ValueCache::addAttrSetChilds(Bindings & children)
 {
     if (!rawCache) return;