Feature: Support DM info from companion plugin even if no sourcemap.json exists (#1216)

* Populate a default sourcemap if plugin provides DM info with no sourcemap.json present

* Add info popup when using only plugin info

* Add unit test

Author: zovits

src/include/Platform/RobloxPlatform.hpp

@@ -106,7 +106,6 @@ class RobloxPlatform : public LSPPlatform
 private:
     // Plugin-provided DataModel information
     PluginNode* pluginInfo = nullptr;
-    Luau::TypedAllocator<PluginNode> pluginNodeAllocator;
 
     mutable std::unordered_map<Uri, const SourceNode*, UriHash> realPathsToSourceNodes{};
     mutable std::unordered_map<Luau::ModuleName, const SourceNode*> virtualPathsToSourceNodes{};
@@ -117,19 +116,24 @@ class RobloxPlatform : public LSPPlatform
     static Luau::ModuleName getVirtualPathFromSourceNode(const SourceNode* sourceNode);
 
     void clearSourcemapTypes();
-    bool updateSourceMap();
 
 public:
     // The root source node from a parsed Rojo source map
     SourceNode* rootSourceNode = nullptr;
     Luau::TypedAllocator<SourceNode> sourceNodeAllocator;
+    Luau::TypedAllocator<PluginNode> pluginNodeAllocator;
 
     Luau::TypeArena instanceTypes;
 
-    /// For testing only
+    /// These are "private" but exposed for unit testing only
+    void setPluginInfo(PluginNode* info)
+    {
+        pluginInfo = info;
+    }
+    bool updateSourceMap();
     bool updateSourceMapFromContents(const std::string& sourceMapContents);
-    /// For testing only
     void writePathsToMap(SourceNode* node, const std::string& base);
+
     std::optional<Uri> getRealPathFromSourceNode(const SourceNode* sourceNode) const;
 
     void mutateRegisteredDefinitions(Luau::GlobalTypes& globals, std::optional<nlohmann::json> metadata) override;

src/platform/roblox/RobloxSourcemap.cpp

@@ -445,18 +445,33 @@ bool RobloxPlatform::updateSourceMap()
     auto config = workspaceFolder->client->getConfiguration(workspaceFolder->rootUri);
     std::string sourcemapFileName = config.sourcemap.sourcemapFile;
 
+    // TODO: we assume the sourcemap file is in the workspace root
     auto sourcemapPath = workspaceFolder->rootUri.resolvePath(sourcemapFileName);
-    workspaceFolder->client->sendTrace("Updating sourcemap contents from " + sourcemapPath.toString());
 
-    // Read in the sourcemap
-    // TODO: we assume a sourcemap file in the workspace root
-    if (auto sourceMapContents = Luau::FileUtils::readFile(sourcemapPath.fsPath()))
+    if (Luau::FileUtils::exists(sourcemapPath.fsPath()))
     {
-        return updateSourceMapFromContents(sourceMapContents.value());
+        if (auto sourceMapContents = Luau::FileUtils::readFile(sourcemapPath.fsPath()))
+        {
+            workspaceFolder->client->sendTrace("Updating sourcemap contents from " + sourcemapPath.toString());
+            return updateSourceMapFromContents(sourceMapContents.value());
+        }
+        else
+        {
+            workspaceFolder->client->sendTrace("Sourcemap file failed to read");
+            return false;
+        }
+    }
+    else if (pluginInfo)
+    {
+        workspaceFolder->client->sendTrace("Creating sourcemap from plugin provided information");
+        workspaceFolder->client->sendWindowMessage(
+            lsp::MessageType::Info, "Couldn't find " + sourcemapFileName + " for workspace '" + workspaceFolder->name +
+                                        "'. Using available datamodel info from companion plugin (require paths may be missing)");
+        return updateSourceMapFromContents("{\"name\":\"Default\",\"className\":\"DataModel\",\"children\":[]}");
     }
     else
     {
-        workspaceFolder->client->sendTrace("Sourcemap file failed to read");
+        workspaceFolder->client->sendTrace("No sourcemap file or plugin information found, cannot update sourcemap");
         return false;
     }
 }

src/platform/roblox/RobloxStudioPlugin.cpp

@@ -26,7 +26,7 @@ void RobloxPlatform::onStudioPluginFullChange(const json& dataModel)
     workspaceFolder->client->sendLogMessage(lsp::MessageType::Info, "received full change from studio plugin");
 
     pluginNodeAllocator.clear();
-    pluginInfo = PluginNode::fromJson(dataModel, pluginNodeAllocator);
+    setPluginInfo(PluginNode::fromJson(dataModel, pluginNodeAllocator));
 
     // Mutate the sourcemap with the new information
     updateSourceMap();
@@ -38,7 +38,7 @@ void RobloxPlatform::onStudioPluginClear()
 
     // TODO: properly handle multi-workspace setup
     pluginNodeAllocator.clear();
-    pluginInfo = nullptr;
+    setPluginInfo(nullptr);
 
     // Mutate the sourcemap with the new information
     updateSourceMap();

tests/Sourcemap.test.cpp

@@ -2,6 +2,7 @@
 #include "Fixture.h"
 #include "Platform/RobloxPlatform.hpp"
 #include "ScopedFlags.h"
+#include "LuauFileUtils.hpp"
 
 TEST_SUITE_BEGIN("SourcemapTests");
 
@@ -761,4 +762,46 @@ TEST_CASE_FIXTURE(Fixture, "child_properties_of_game_are_cleared_when_an_invalid
     CHECK_EQ(Luau::get<Luau::UnknownProperty>(result2.errors[0])->key, "Part");
 }
 
+TEST_CASE_FIXTURE(Fixture, "sourcemap_update_uses_plugin_info_if_sourcemap_file_is_missing")
+{
+    client->globalConfig.diagnostics.strictDatamodelTypes = true;
+    client->globalConfig.sourcemap.enabled = true;
+
+    // Verify that no sourcemap file exists - this ensures we're testing the fallback behavior
+    auto config = client->getConfiguration(workspace.rootUri);
+    auto sourcemapPath = workspace.rootUri.resolvePath(config.sourcemap.sourcemapFile);
+    REQUIRE_FALSE(Luau::FileUtils::exists(sourcemapPath.fsPath()));
+
+    // Set up plugin info with a Part child
+    auto platform = dynamic_cast<RobloxPlatform*>(workspace.platform.get());
+    auto pluginData = json::parse(R"(
+        {
+            "Name": "game",
+            "ClassName": "DataModel",
+            "Children": [
+                {
+                    "Name": "TestPart",
+                    "ClassName": "Part"
+                }
+            ]
+        }
+    )");
+    platform->setPluginInfo(PluginNode::fromJson(pluginData, platform->pluginNodeAllocator));
+
+    // Update sourcemap successfully
+    REQUIRE(platform->updateSourceMap());
+
+    // Verify the plugin info was used
+    REQUIRE(platform->rootSourceNode);
+    CHECK_EQ(platform->rootSourceNode->className, "DataModel");
+
+    auto result = check(R"(
+        --!strict
+        local part = game.TestPart
+    )");
+
+    LUAU_LSP_REQUIRE_NO_ERRORS(result);
+    CHECK(Luau::toString(requireType("part")) == "Part");
+}
+
 TEST_SUITE_END();