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authorDaiderd Jordan <daiderd@gmail.com>2020-01-11T14·06+0100
committerEelco Dolstra <edolstra@gmail.com>2020-04-10T08·39+0200
commiteba0892d08dca56905f251cfa9e1d048daf8c31d (patch)
treed98f87ac64d1c5d27a10e7a8de006419c47d0902
parent7fee49ef3719e7359b1b317a5b5a2bf0b4ecc3df (diff)
libexpr: show expression in assertion errors
Includes the expression of the condition in the assertion message if
the assertion failed, making assertions much easier to debug. eg.

    error: assertion (withPython -> (python2Packages != null)) failed at pkgs/tools/security/nmap/default.nix:11:1

(cherry picked from commit 307bcb9a8e7a16bfc451e055a620b766df9d3f7d)
Signed-off-by: Domen Kožar <domen@dev.si>
-rw-r--r--src/libexpr/eval.cc11
1 files changed, 7 insertions, 4 deletions
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 09276a189535..3426afb6cf6e 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -520,9 +520,9 @@ LocalNoInlineNoReturn(void throwTypeError(const char * s, const ExprLambda & fun
     throw TypeError(format(s) % fun.showNamePos() % s2 % pos);
 }
 
-LocalNoInlineNoReturn(void throwAssertionError(const char * s, const Pos & pos))
+LocalNoInlineNoReturn(void throwAssertionError(const char * s, const string & s1, const Pos & pos))
 {
-    throw AssertionError(format(s) % pos);
+    throw AssertionError(format(s) % s1 % pos);
 }
 
 LocalNoInlineNoReturn(void throwUndefinedVarError(const char * s, const string & s1, const Pos & pos))
@@ -1253,8 +1253,11 @@ void ExprIf::eval(EvalState & state, Env & env, Value & v)
 
 void ExprAssert::eval(EvalState & state, Env & env, Value & v)
 {
-    if (!state.evalBool(env, cond, pos))
-        throwAssertionError("assertion failed at %1%", pos);
+    if (!state.evalBool(env, cond, pos)) {
+        std::ostringstream out;
+        cond->show(out);
+        throwAssertionError("assertion %1% failed at %2%", out.str(), pos);
+    }
     body->eval(state, env, v);
 }