Improve the data formatter UX if an array is uninitialized.

lldb/source/Plugins/Language/Swift/SwiftArray.cpp

@@ -114,7 +114,7 @@ SwiftArrayNativeBufferHandler::SwiftArrayNativeBufferHandler(
 }
 
 bool SwiftArrayNativeBufferHandler::IsValid() {
-  return m_metadata_ptr != LLDB_INVALID_ADDRESS &&
+  return m_metadata_ptr != LLDB_INVALID_ADDRESS && m_metadata_ptr &&
          m_first_elem_ptr != LLDB_INVALID_ADDRESS && m_capacity >= m_size &&
          m_elem_type.IsValid();
 }
@@ -437,10 +437,7 @@ SwiftArrayBufferHandler::CreateBufferHandler(ValueObject &static_valobj) {
         handler.reset(new SwiftArrayBridgedBufferHandler(
             process_sp, masked_storage_location));
       }
-
-      if (handler && handler->IsValid())
-        return handler;
-      return nullptr;
+      return handler;
     } else {
       CompilerType elem_type(
           valobj.GetCompilerType().GetArrayElementType(exe_scope));
@@ -457,6 +454,12 @@ bool lldb_private::formatters::swift::Array_SummaryProvider(
   if (!handler)
     return false;
 
+  if (!handler->IsValid()) {
+    // FIXME: This should be an out-of-band llvm::Error return value.
+    stream << "<uninitialized>";
+    return true;
+  }
+
   auto count = handler->GetCount();
 
   stream.Printf("%zu value%s", count, (count == 1 ? "" : "s"));

lldb/test/API/lang/swift/array_uninitialized/Makefile

@@ -0,0 +1,3 @@
+SWIFT_SOURCES := main.swift
+SWIFTFLAGS_EXTRAS := -parse-as-library
+include Makefile.rules

lldb/test/API/lang/swift/array_uninitialized/TestSwiftArrayUninitialized.py

@@ -0,0 +1,15 @@
+import lldb
+from lldbsuite.test.decorators import *
+import lldbsuite.test.lldbtest as lldbtest
+import lldbsuite.test.lldbutil as lldbutil
+
+
+class TestSwiftArrayUninitialized(lldbtest.TestBase):
+    @swiftTest
+    def test(self):
+        """Test unitialized global arrays"""
+        self.build()
+        lldbutil.run_to_source_breakpoint(
+            self, 'break here', lldb.SBFileSpec('main.swift'))
+        self.expect("target variable -- array_unused", substrs=['<uninitialized>'])
+        self.expect("target variable -- array_used_empty", substrs=['0 values'])

lldb/test/API/lang/swift/array_uninitialized/main.swift

@@ -0,0 +1,8 @@
+var array_unused : [Int] = [1,2,3]
+var array_used_empty : [Int] = []
+@main struct Main {
+  static func main() {
+    print(array_used_empty)
+    print("break here")
+  }
+}

lldb/test/API/lang/swift/nsarray_code_running_formatter/main.swift

@@ -23,7 +23,7 @@ func main() {
   var tb = Test() as Array + []
 
   print("second stop") //% self.expect('frame variable -d run -- t', substrs=['t = 0x', 'NSArray = {', 'NSObject = {'])
-                       //% self.expect('frame variable -d run -- ta', substrs=['ta = {', '_buffer = {', '_storage =', 'rawValue = 0x'])
+                       //% self.expect('frame variable -d run -- ta', substrs=['ta = <uninitialized>', '_buffer = {', '_storage =', 'rawValue = 0x'])
                        //% self.expect('frame variable -d run -- tb', substrs=['tb = 1 value {', '"abc"'])
                        //% self.expect('po t', substrs=['0 : abc'])
                        //% self.expect('po ta', substrs=['0 : abc'])