[Basic] Add a utility function for parsing an editor placeholder.

Swift SVN r26214

Author: akyrtzi

include/swift/Basic/EditorPlaceholder.h

@@ -0,0 +1,52 @@
+//===--- EditorPlaceholder.h - Handling for editor placeholders -----------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Provides info about editor placeholders, <#such as this#>.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_BASIC_EDITORPLACEHOLDER_H
+#define SWIFT_BASIC_EDITORPLACEHOLDER_H
+
+#include "llvm/ADT/StringRef.h"
+#include "swift/Basic/LLVM.h"
+
+namespace swift {
+
+enum class EditorPlaceholderKind {
+  Basic,
+  Typed,
+};
+
+struct EditorPlaceholderData {
+  /// Placeholder kind.
+  EditorPlaceholderKind Kind;
+  /// The part that is displayed in the editor.
+  StringRef Display;
+  /// If kind is \c Typed, this is the type string for the placeholder.
+  StringRef Type;
+  /// If kind is \c Typed, this is the type string to be considered for
+  /// placeholder expansion.
+  /// It can be same as \c Type or different if \c Type is a typealias.
+  StringRef TypeForExpansion;
+};
+
+/// Deconstructs a placeholder string and returns info about it.
+/// \returns None if the \c PlaceholderText is not a valid placeholder string.
+Optional<EditorPlaceholderData>
+  parseEditorPlaceholder(StringRef PlaceholderText);
+
+} // namespace swift
+
+#endif // LLVM_SWIFT_BASIC_EDITORPLACEHOLDER_H
+

lib/Basic/CMakeLists.txt

@@ -7,6 +7,7 @@ add_swift_library(swiftBasic
   DemangleWrappers.cpp
   DiagnosticConsumer.cpp
   DiverseStack.cpp
+  EditorPlaceholder.cpp
   JSONSerialization.cpp
   LangOptions.cpp
   Platform.cpp

lib/Basic/EditorPlaceholder.cpp

@@ -0,0 +1,78 @@
+//===--- EditorPlaceholder.cpp - Handling for editor placeholders ---------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Provides info about editor placeholders, <#such as this#>.
+///
+//===----------------------------------------------------------------------===//
+
+#include "swift/Basic/EditorPlaceholder.h"
+#include "llvm/ADT/Optional.h"
+
+using namespace swift;
+using namespace llvm;
+
+// Placeholder text must start with '<#' and end with
+// '#>'.
+//
+// Placeholder kinds:
+//
+// Typed:
+//   'T##' display-string '##' type-string ('##' type-for-expansion-string)?
+//
+// Basic:
+//   display-string
+//
+// NOTE: It is required that '##' is not a valid substring of display-string
+// or type-string. If this ends up not the case for some reason, we can consider
+// adding escaping for '##'.
+
+Optional<EditorPlaceholderData>
+swift::parseEditorPlaceholder(StringRef PlaceholderText) {
+  if (!PlaceholderText.startswith("<#") ||
+      !PlaceholderText.endswith("#>"))
+    return None;
+
+  PlaceholderText = PlaceholderText.drop_front(2).drop_back(2);
+  EditorPlaceholderData PHDataBasic;
+  PHDataBasic.Kind = EditorPlaceholderKind::Basic;
+  PHDataBasic.Display = PlaceholderText;
+
+  if (!PlaceholderText.startswith("T##")) {
+    // Basic.
+    return PHDataBasic;
+  }
+
+  // Typed.
+  EditorPlaceholderData PHDataTyped;
+  PHDataTyped.Kind = EditorPlaceholderKind::Typed;
+
+  assert(PlaceholderText.startswith("T##"));
+  PlaceholderText = PlaceholderText.drop_front(3);
+  size_t Pos = PlaceholderText.find("##");
+  if (Pos == StringRef::npos) {
+    // Fallback to basic.
+    return PHDataBasic;
+  }
+  PHDataTyped.Display = PlaceholderText.substr(0, Pos);
+
+  PlaceholderText = PlaceholderText.substr(Pos+2);
+  Pos = PlaceholderText.find("##");
+  if (Pos == StringRef::npos) {
+    PHDataTyped.Type = PHDataTyped.TypeForExpansion = PlaceholderText;
+  } else {
+    PHDataTyped.Type = PlaceholderText.substr(0, Pos);
+    PHDataTyped.TypeForExpansion = PlaceholderText.substr(Pos+2);
+  }
+
+  return PHDataTyped;
+}

unittests/Basic/CMakeLists.txt

@@ -9,6 +9,7 @@ add_swift_unittest(SwiftBasicTests
   ADTTests.cpp
   ClusteredBitVectorTest.cpp
   Demangle.cpp
+  EditorPlaceholderTest.cpp
   SourceManager.cpp
   TreeScopedHashTableTests.cpp
   StringExtrasTest.cpp

unittests/Basic/EditorPlaceholderTest.cpp

@@ -0,0 +1,54 @@
+#include "swift/Basic/EditorPlaceholder.h"
+#include "llvm/ADT/Optional.h"
+#include "gtest/gtest.h"
+
+using namespace swift;
+
+TEST(EditorPlaceholder, EditorPlaceholders) {
+  const char *Text = "<#this is simple#>";
+  EditorPlaceholderData Data = *parseEditorPlaceholder(Text);
+  EXPECT_EQ(EditorPlaceholderKind::Basic, Data.Kind);
+  EXPECT_EQ("this is simple", Data.Display);
+  EXPECT_TRUE(Data.Type.empty());
+  EXPECT_TRUE(Data.TypeForExpansion.empty());
+
+  Text = "<#T##x: Int##Int#>";
+  Data = *parseEditorPlaceholder(Text);
+  EXPECT_EQ(EditorPlaceholderKind::Typed, Data.Kind);
+  EXPECT_EQ("x: Int", Data.Display);
+  EXPECT_EQ("Int", Data.Type);
+  EXPECT_EQ("Int", Data.TypeForExpansion);
+
+  Text = "<#T##x: Int##Blah##()->Int#>";
+  Data = *parseEditorPlaceholder(Text);
+  EXPECT_EQ(EditorPlaceholderKind::Typed, Data.Kind);
+  EXPECT_EQ("x: Int", Data.Display);
+  EXPECT_EQ("Blah", Data.Type);
+  EXPECT_EQ("()->Int", Data.TypeForExpansion);
+
+  // Fallback.
+  Text = "<#T##x: Int#>";
+  Data = *parseEditorPlaceholder(Text);
+  EXPECT_EQ(EditorPlaceholderKind::Basic, Data.Kind);
+  EXPECT_EQ("T##x: Int", Data.Display);
+  EXPECT_TRUE(Data.Type.empty());
+  EXPECT_TRUE(Data.TypeForExpansion.empty());
+}
+
+TEST(EditorPlaceholder, InvalidEditorPlaceholders) {
+  const char *Text = "<#foo";
+  Optional<EditorPlaceholderData> DataOpt = parseEditorPlaceholder(Text);
+  EXPECT_FALSE(DataOpt.hasValue());
+
+  Text = "foo#>";
+  DataOpt = parseEditorPlaceholder(Text);
+  EXPECT_FALSE(DataOpt.hasValue());
+
+  Text = "#foo#>";
+  DataOpt = parseEditorPlaceholder(Text);
+  EXPECT_FALSE(DataOpt.hasValue());
+
+  Text = " <#foo#>";
+  DataOpt = parseEditorPlaceholder(Text);
+  EXPECT_FALSE(DataOpt.hasValue());
+}