Handle autocomplete in table when no initial character present (#1155)

Closes #685

Analysis/src/Autocomplete.cpp

@@ -16,6 +16,7 @@
 LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);
 LUAU_FASTFLAG(DebugLuauReadWriteProperties);
 LUAU_FASTFLAGVARIABLE(LuauAutocompleteStringLiteralBounds, false);
+LUAU_FASTFLAGVARIABLE(LuauAutocompleteTableKeysNoInitialCharacter, false);
 
 static const std::unordered_set<std::string> kStatementStartingKeywords = {
     "while", "if", "local", "repeat", "function", "do", "for", "return", "break", "continue", "type", "export"};
@@ -1742,6 +1743,37 @@ static AutocompleteResult autocomplete(const SourceModule& sourceModule, const M
             }
         }
     }
+    else if (AstExprTable* exprTable = node->as<AstExprTable>(); exprTable && FFlag::LuauAutocompleteTableKeysNoInitialCharacter)
+    {
+        AutocompleteEntryMap result;
+
+        if (auto it = module->astExpectedTypes.find(exprTable))
+        {
+            result = autocompleteProps(*module, typeArena, builtinTypes, *it, PropIndexType::Key, ancestry);
+
+            // If the key type is a union of singleton strings,
+            // suggest those too.
+            if (auto ttv = get<TableType>(follow(*it)); ttv && ttv->indexer)
+            {
+                autocompleteStringSingleton(ttv->indexer->indexType, false, node, position, result);
+            }
+
+            // Remove keys that are already completed
+            for (const auto& item : exprTable->items)
+            {
+                if (!item.key)
+                    continue;
+
+                if (auto stringKey = item.key->as<AstExprConstantString>())
+                    result.erase(std::string(stringKey->value.data, stringKey->value.size));
+            }
+        }
+
+        // Also offer general expression suggestions
+        autocompleteExpression(sourceModule, *module, builtinTypes, typeArena, ancestry, position, result);
+
+        return {result, ancestry, AutocompleteContext::Property};
+    }
     else if (isIdentifier(node) && (parent->is<AstStatExpr>() || parent->is<AstStatError>()))
         return {autocompleteStatement(sourceModule, *module, ancestry, position), ancestry, AutocompleteContext::Statement};
 

tests/Autocomplete.test.cpp

@@ -16,6 +16,7 @@
 LUAU_FASTFLAG(LuauTraceTypesInNonstrictMode2)
 LUAU_FASTFLAG(LuauSetMetatableDoesNotTimeTravel)
 LUAU_FASTFLAG(LuauAutocompleteStringLiteralBounds);
+LUAU_FASTFLAG(LuauAutocompleteTableKeysNoInitialCharacter)
 
 using namespace Luau;
 
@@ -2693,6 +2694,43 @@ local t = {
     CHECK_EQ(ac.context, AutocompleteContext::Property);
 }
 
+TEST_CASE_FIXTURE(ACFixture, "suggest_table_keys_no_initial_character")
+{
+    ScopedFastFlag sff{FFlag::LuauAutocompleteTableKeysNoInitialCharacter, true};
+
+    check(R"(
+type Test = { first: number, second: number }
+local t: Test = { @1 }
+    )");
+
+    auto ac = autocomplete('1');
+    CHECK(ac.entryMap.count("first"));
+    CHECK(ac.entryMap.count("second"));
+    CHECK_EQ(ac.context, AutocompleteContext::Property);
+
+    check(R"(
+type Test = { first: number, second: number }
+local t: Test = { first = 1, @1 }
+    )");
+
+    ac = autocomplete('1');
+    CHECK_EQ(ac.entryMap.count("first"), 0);
+    CHECK(ac.entryMap.count("second"));
+    CHECK_EQ(ac.context, AutocompleteContext::Property);
+
+    check(R"(
+type Properties = { TextScaled: boolean, Text: string }
+local function create(props: Properties) end
+
+create({ @1 })
+    )");
+
+    ac = autocomplete('1');
+    CHECK(ac.entryMap.count("TextScaled"));
+    CHECK(ac.entryMap.count("Text"));
+    CHECK_EQ(ac.context, AutocompleteContext::Property);
+}
+
 TEST_CASE_FIXTURE(ACFixture, "autocomplete_documentation_symbols")
 {
     loadDefinition(R"(