From c4c120513ff965b117bc006be6f98e227b74e1ae Mon Sep 17 00:00:00 2001
From: JohnnyMorganz <johnnymorganz@outlook.com>
Date: Thu, 20 Oct 2022 17:07:00 +0100
Subject: [PATCH] Fix reverse deps > 1 node away not correctly marked as dirty
 (#719)

`Frontend.markDirty()` does not correctly mark reverse dependencies that
are not immediate as dirty.
This is because it would keep adding the reverse deps of `name` into the
queue to mark as dirty, instead of the reverse deps of `next`
---
 Analysis/src/Frontend.cpp | 24 +++++++++++++++++++-----
 tests/Frontend.test.cpp   | 27 +++++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 5 deletions(-)

diff --git a/Analysis/src/Frontend.cpp b/Analysis/src/Frontend.cpp
index 5705ac1..cfe710d 100644
--- a/Analysis/src/Frontend.cpp
+++ b/Analysis/src/Frontend.cpp
@@ -30,6 +30,7 @@ LUAU_FASTFLAGVARIABLE(LuauAutocompleteDynamicLimits, false)
 LUAU_FASTINTVARIABLE(LuauAutocompleteCheckTimeoutMs, 100)
 LUAU_FASTFLAGVARIABLE(DebugLuauDeferredConstraintResolution, false)
 LUAU_FASTFLAG(DebugLuauLogSolverToJson);
+LUAU_FASTFLAGVARIABLE(LuauFixMarkDirtyReverseDeps, false)
 
 namespace Luau
 {
@@ -807,13 +808,26 @@ void Frontend::markDirty(const ModuleName& name, std::vector<ModuleName>* marked
         sourceNode.dirtyModule = true;
         sourceNode.dirtyModuleForAutocomplete = true;
 
-        if (0 == reverseDeps.count(name))
-            continue;
+        if (FFlag::LuauFixMarkDirtyReverseDeps)
+        {
+            if (0 == reverseDeps.count(next))
+                continue;
 
-        sourceModules.erase(name);
+            sourceModules.erase(next);
 
-        const std::vector<ModuleName>& dependents = reverseDeps[name];
-        queue.insert(queue.end(), dependents.begin(), dependents.end());
+            const std::vector<ModuleName>& dependents = reverseDeps[next];
+            queue.insert(queue.end(), dependents.begin(), dependents.end());
+        }
+        else
+        {
+            if (0 == reverseDeps.count(name))
+                continue;
+
+            sourceModules.erase(name);
+
+            const std::vector<ModuleName>& dependents = reverseDeps[name];
+            queue.insert(queue.end(), dependents.begin(), dependents.end());
+        }
     }
 }
 
diff --git a/tests/Frontend.test.cpp b/tests/Frontend.test.cpp
index 957f3c7..df0abdc 100644
--- a/tests/Frontend.test.cpp
+++ b/tests/Frontend.test.cpp
@@ -517,6 +517,33 @@ TEST_CASE_FIXTURE(FrontendFixture, "recheck_if_dependent_script_is_dirty")
     CHECK_EQ("{| b_value: string |}", toString(*bExports));
 }
 
+TEST_CASE_FIXTURE(FrontendFixture, "mark_non_immediate_reverse_deps_as_dirty")
+{
+    ScopedFastFlag sff[] = {
+        {"LuauFixMarkDirtyReverseDeps", true},
+    };
+
+    fileResolver.source["game/Gui/Modules/A"] = "return {hello=5, world=true}";
+    fileResolver.source["game/Gui/Modules/B"] = R"(
+        return require(game:GetService('Gui').Modules.A)
+    )";
+    fileResolver.source["game/Gui/Modules/C"] = R"(
+        local Modules = game:GetService('Gui').Modules
+        local B = require(Modules.B)
+        return {c_value = B.hello}
+    )";
+
+    frontend.check("game/Gui/Modules/C");
+
+    std::vector<Luau::ModuleName> markedDirty;
+    frontend.markDirty("game/Gui/Modules/A", &markedDirty);
+
+    REQUIRE(markedDirty.size() == 3);
+    CHECK(std::find(markedDirty.begin(), markedDirty.end(), "game/Gui/Modules/A") != markedDirty.end());
+    CHECK(std::find(markedDirty.begin(), markedDirty.end(), "game/Gui/Modules/B") != markedDirty.end());
+    CHECK(std::find(markedDirty.begin(), markedDirty.end(), "game/Gui/Modules/C") != markedDirty.end());
+}
+
 #if 0
 // Does not work yet. :(
 TEST_CASE_FIXTURE(FrontendFixture, "recheck_if_dependent_script_has_a_parse_error")