From 9151dbff88fa765496e970aee2db5a8ce640b3a4 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 2 Jun 2022 10:26:46 -0600
Subject: [PATCH] ignore-try flag

---
 src/libcmd/command.cc  | 11 ++++++++++-
 src/libcmd/command.hh  |  1 +
 src/libexpr/eval.cc    |  1 +
 src/libexpr/eval.hh    |  1 +
 src/libexpr/primops.cc | 14 ++++++++++++++
 5 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 7f8072d75..940fd5b23 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -91,6 +91,12 @@ EvalCommand::EvalCommand()
         .description = "start an interactive environment if evaluation fails",
         .handler = {&startReplOnEvalErrors, true},
     });
+
+    addFlag({
+        .longName = "ignore-try",
+        .description = "ignore exceptions in try clauses during debug",
+        .handler = {&ignoreExceptionsDuringTry, true},
+    });
 }
 
 EvalCommand::~EvalCommand()
@@ -120,7 +126,10 @@ ref<EvalState> EvalCommand::getEvalState()
             ;
 
         if (startReplOnEvalErrors) {
-            evalState->debugRepl = &runRepl;        
+            evalState->debugRepl = &runRepl;
+        };
+        if (ignoreExceptionsDuringTry) {
+            evalState->ignoreTry = ignoreExceptionsDuringTry;
         };
     }
     return ref<EvalState>(evalState);
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index 8982f21d0..2c930dcb7 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -58,6 +58,7 @@ struct CopyCommand : virtual StoreCommand
 struct EvalCommand : virtual StoreCommand, MixEvalArgs
 {
     bool startReplOnEvalErrors = false;
+    bool ignoreExceptionsDuringTry = false;
 
     EvalCommand();
 
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 40462afdf..c35527992 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -467,6 +467,7 @@ EvalState::EvalState(
     , debugRepl(0)
     , debugStop(false)
     , debugQuit(false)
+    , ignoreTry(false)
     , regexCache(makeRegexCache())
 #if HAVE_BOEHMGC
     , valueAllocCache(std::allocate_shared<void *>(traceable_allocator<void *>(), nullptr))
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 7b8732169..3c3dddd1e 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -130,6 +130,7 @@ public:
     void (* debugRepl)(ref<EvalState> es, const ValMap & extraEnv);
     bool debugStop;
     bool debugQuit;
+    bool ignoreTry;
     std::list<DebugTrace> debugTraces;
     std::map<const Expr*, const std::shared_ptr<const StaticEnv>> exprEnvs;
     const std::shared_ptr<const StaticEnv> getStaticEnv(const Expr & expr) const
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index eea274301..772898932 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -851,6 +851,15 @@ static RegisterPrimOp primop_floor({
 static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Value & v)
 {
     auto attrs = state.buildBindings(2);
+
+    void (* savedDebugRepl)(ref<EvalState> es, const ValMap & extraEnv) = nullptr;
+    if (state.debugRepl && state.ignoreTry)
+    {
+        // to prevent starting the repl from exceptions withing a tryEval, null it.
+        savedDebugRepl = state.debugRepl;
+        state.debugRepl = nullptr;
+    }
+
     try {
         state.forceValue(*args[0], pos);
         attrs.insert(state.sValue, args[0]);
@@ -859,6 +868,11 @@ static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Va
         attrs.alloc(state.sValue).mkBool(false);
         attrs.alloc("success").mkBool(false);
     }
+
+    // restore the debugRepl pointer if we saved it earlier.
+    if (savedDebugRepl)
+        state.debugRepl = savedDebugRepl;
+
     v.mkAttrs(attrs);
 }