Start the Migrator library

The Swift 4 Migrator is invoked through either the driver and frontend
with the -update-code flag.

The basic pipeline in the frontend is:

- Perform some list of syntactic fixes (there are currently none).
- Perform N rounds of sema fix-its on the primary input file, currently
  set to 7 based on prior migrator seasons.  Right now, this is just set
  to take any fix-it suggested by the compiler.
- Emit a replacement map file, a JSON file describing replacements to a
  file that Xcode knows how to understand.

Currently, the Migrator maintains a history of migration states along
the way for debugging purposes.

- Add -emit-remap frontend option
  This will indicate the EmitRemap frontend action.
- Don't fork to a separte swift-update binary.
  This is going to be a mode of the compiler, invoked by the same flags.
- Add -disable-migrator-fixits option
  Useful for debugging, this skips the phase in the Migrator that
  automatically applies fix-its suggested by the compiler.
- Add -emit-migrated-file-path option
  This is used for testing/debugging scenarios. This takes the final
  migration state's output text and writes it to the file specified
  by this option.
- Add -dump-migration-states-dir

  This dumps all of the migration states encountered during a migration
  run for a file to the given directory. For example, the compiler
  fix-it migration pass dumps the input file, the output file, and the
  remap file between the two.

  State output has the following naming convention:
  ${Index}-${MigrationPassName}-${What}.${extension}, such as:
  1-FixitMigrationState-Input.swift

rdar://problem/30926261

Author: bitjammer

include/swift/Basic/SourceManager.h

@@ -199,6 +199,8 @@ class SourceManager {
     return LLVMSourceMgr.FindLineNumber(Loc.Value, BufferID);
   }
 
+  StringRef getEntireTextForBuffer(unsigned BufferID) const;
+
   StringRef extractText(CharSourceRange Range,
                         Optional<unsigned> BufferID = None) const;
 

include/swift/Driver/Driver.h

@@ -66,9 +66,6 @@ class OutputInfo {
 
     /// Compile and execute the inputs immediately
     Immediate,
-
-    /// Invoke swift-update with the compiler frontend options.
-    UpdateCode,
   };
 
   /// The mode in which the driver should invoke the frontend.
@@ -97,9 +94,6 @@ class OutputInfo {
 
   /// Whether the compiler picked the current module name, rather than the user.
   bool ModuleNameIsFallback = false;
-
-  // Whether the driver should generate compiler fixits as source edits.
-  bool ShouldGenerateFixitEdits = false;
 
   /// The number of threads for multi-threaded compilation.
   unsigned numThreads = 0;

include/swift/Frontend/Frontend.h

@@ -33,6 +33,7 @@
 #include "swift/ClangImporter/ClangImporter.h"
 #include "swift/ClangImporter/ClangImporterOptions.h"
 #include "swift/Frontend/FrontendOptions.h"
+#include "swift/Migrator/MigratorOptions.h"
 #include "swift/Sema/SourceLoader.h"
 #include "swift/Serialization/Validation.h"
 #include "swift/SIL/SILModule.h"
@@ -62,6 +63,7 @@ class CompilerInvocation {
   ClangImporterOptions ClangImporterOpts;
   SearchPathOptions SearchPathOpts;
   DiagnosticOptions DiagnosticOpts;
+  MigratorOptions MigratorOpts;
   SILOptions SILOpts;
   IRGenOptions IRGenOpts;
 
@@ -202,6 +204,10 @@ class CompilerInvocation {
     return DiagnosticOpts;
   }
 
+  const MigratorOptions &getMigratorOptions() const {
+    return MigratorOpts;
+  }
+
   SILOptions &getSILOptions() { return SILOpts; }
   const SILOptions &getSILOptions() const { return SILOpts; }
 

include/swift/Frontend/FrontendOptions.h

@@ -169,6 +169,8 @@ class FrontendOptions {
     EmitIR, ///< Emit LLVM IR
     EmitBC, ///< Emit LLVM BC
     EmitObject, ///< Emit object file
+
+    UpdateCode, ///< Update Swift code
   };
 
   /// Indicates the action the user requested that the frontend perform.

include/swift/Migrator/FixitApplyDiagnosticConsumer.h

@@ -0,0 +1,86 @@
+//===--- FixitApplyDiagnosticConsumer.h - ----------------------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// This class records compiler interesting fix-its as textual edits.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_MIGRATOR_FIXITAPPLYDIAGNOSTICCONSUMER_H
+#define SWIFT_MIGRATOR_FIXITAPPLYDIAGNOSTICCONSUMER_H
+
+#include "swift/AST/DiagnosticConsumer.h"
+#include "clang/Rewrite/Core/RewriteBuffer.h"
+
+namespace swift {
+
+class CompilerInvocation;
+struct DiagnosticInfo;
+struct MigratorOptions;
+class SourceManager;
+
+namespace migrator {
+
+class Replacement;
+
+class FixitApplyDiagnosticConsumer final : public DiagnosticConsumer {
+  clang::RewriteBuffer RewriteBuf;
+
+  /// The Migrator options collected by the Swift CompilerInvocation,
+  /// used to drive decisions about which fix-its to apply.
+  const MigratorOptions &MigratorOpts;
+
+  /// The entire text of the input file.
+  const StringRef Text;
+
+  /// The name of the buffer, which should be the absolute path of the input
+  /// filename.
+  const StringRef BufferName;
+
+  /// The number of fix-its pushed into the rewrite buffer. Use this to
+  /// determine whether to call `printResult`.
+  unsigned NumFixitsApplied;
+
+  /// A list of replacements that have been applied while diagnosing the
+  /// input file.
+  std::vector<Replacement> Replacements;
+
+  /// Returns true if the fix-it should be applied.
+  bool shouldTakeFixit(const DiagnosticInfo &Info,
+                       const DiagnosticInfo::FixIt &F) const;
+
+public:
+  FixitApplyDiagnosticConsumer(const MigratorOptions &MigratorOpts,
+                               const StringRef Text,
+                               const StringRef BufferName);
+
+  /// Print the resulting text, applying the caught fix-its to the given
+  /// output stream.
+  void printResult(llvm::raw_ostream &OS) const;
+
+  const std::vector<Replacement> &getReplacements() const {
+    return Replacements;
+  }
+
+  void handleDiagnostic(SourceManager &SM, SourceLoc Loc,
+                        DiagnosticKind Kind,
+                        StringRef FormatString,
+                        ArrayRef<DiagnosticArgument> FormatArgs,
+                        const DiagnosticInfo &Info) override;
+
+  unsigned getNumFixitsApplied() const {
+    return NumFixitsApplied;
+  }
+};
+} // end namespace migrator
+} // end namespace swift
+
+#endif // SWIFT_MIGRATOR_FIXITAPPLYDIAGNOSTICCONSUMER_H

include/swift/Migrator/MigrationState.h

@@ -0,0 +1,121 @@
+//===--- MigrationState.h - Migration State --------------------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// This class is an explicit container for a state during migration, its input
+// and output text, as well as what created this state.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_MIGRATOR_MIGRATIONSTATE_H
+#define SWIFT_MIGRATOR_MIGRATIONSTATE_H
+
+#include "swift/Migrator/Replacement.h"
+#include "swift/Syntax/References.h"
+#include "llvm/ADT/IntrusiveRefCntPtr.h"
+#include "llvm/ADT/StringRef.h"
+
+namespace swift {
+
+class SourceManager;
+
+namespace migrator {
+
+enum class MigrationKind {
+  /// The compiler has made several passes over the input file and we
+  /// applied the suggested fix-its we deemed appropriate.
+  CompilerFixits,
+};
+
+struct MigrationState : public llvm::ThreadSafeRefCountedBase<MigrationState> {
+  const MigrationKind Kind;
+  SourceManager &SrcMgr;
+
+  MigrationState(const MigrationKind Kind, SourceManager &SrcMgr)
+    : Kind(Kind), SrcMgr(SrcMgr) {}
+
+  MigrationKind getKind() const {
+    return Kind;
+  }
+
+  std::string getInputText() const;
+  std::string getOutputText() const;
+
+  /// Write all relevant information about the state to OutDir, such as the
+  /// input file, output file, replacements, syntax trees, etc.
+  bool print(size_t StateNumber, StringRef OutDir) const;
+};
+
+struct FixitMigrationState final : public MigrationState {
+  const unsigned InputBufferID;
+  const unsigned OutputBufferID;
+  const std::vector<Replacement> Replacements;
+
+  // Other information about the migration?
+
+  FixitMigrationState(SourceManager &SrcMgr,
+                      const unsigned InputBufferID,
+                      const unsigned OutputBufferID,
+                      const std::vector<Replacement> &Replacements)
+    : MigrationState(MigrationKind::CompilerFixits, SrcMgr),
+      InputBufferID(InputBufferID),
+      OutputBufferID(OutputBufferID),
+      Replacements(Replacements) {}
+
+  std::string getInputText() const;
+
+  unsigned getInputBufferID() const {
+    return InputBufferID;
+  }
+
+  std::string getOutputText() const;
+
+  unsigned getOutputBufferID() const {
+    return OutputBufferID;
+  }
+
+  bool print(size_t StateNumber, StringRef OutDir) const;
+
+  bool outputDiffersFromInput() const {
+    return InputBufferID != OutputBufferID;
+  }
+
+  /// Dump the remap between the current input and output text.
+  void dumpRemap() const;
+
+  static RC<FixitMigrationState>
+  make(SourceManager &SrcMgr, const unsigned InputBufferID,
+       const unsigned OutputBufferID,
+       const std::vector<Replacement> &Replacements) {
+    return RC<FixitMigrationState> {
+      new FixitMigrationState {
+        SrcMgr,
+        InputBufferID,
+        // The input is the output here, because nothing happened yet.
+        OutputBufferID,
+        Replacements
+      }
+    };
+  }
+
+  static RC<FixitMigrationState>
+  start(SourceManager &SrcMgr, const unsigned InputBufferID) {
+    return make(SrcMgr, InputBufferID, InputBufferID, {});
+  }
+
+  static bool classof(const MigrationState *MS) {
+    return MS->getKind() == MigrationKind::CompilerFixits;
+  }
+};
+
+}
+}
+#endif // SWIFT_MIGRATOR_MIGRATIONSTATE_H

include/swift/Migrator/Migrator.h

@@ -0,0 +1,87 @@
+//===--- Migrator.h - Migrator ----------------------------------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// The top-level Swift Migrator driver.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_MIGRATOR_MIGRATOR_H
+#define SWIFT_MIGRATOR_MIGRATOR_H
+
+#include "swift/Migrator/MigrationState.h"
+#include "swift/Migrator/Replacement.h"
+#include "swift/Syntax/References.h"
+
+namespace swift {
+class CompilerInstance;
+
+namespace migrator {
+
+/// Run the migrator on the compiler invocation's input file and emit a
+/// "replacement map" describing the requested changes to the source file.
+bool updateCodeAndEmitRemap(CompilerInstance &Instance,
+                            const CompilerInvocation &Invocation);
+
+class Migrator {
+  CompilerInstance &StartInstance;
+  const CompilerInvocation &StartInvocation;
+  SourceManager SrcMgr;
+  std::vector<RC<MigrationState>> States;
+
+public:
+  Migrator(CompilerInstance &StartInstance,
+           const CompilerInvocation &StartInvocation);
+
+  /// The maximum number of times to run the compiler over the input to get
+  /// fix-its. Nullability changes may expose other fix-its in subsequent
+  /// compilations.
+  static constexpr unsigned MaxCompilerFixitPassIterations = 7;
+
+  /// Repeatedly perform a number of compielr-fix-it migrations in a row, until
+  /// there are no new suggestions from the compiler or some other error
+  /// occurred.
+  void repeatFixitMigrations(const unsigned Iterations);
+
+  /// Perform a single compiler fix-it migration on the last state, and push
+  /// the result onto the state history.
+  llvm::Optional<RC<FixitMigrationState>> performAFixItMigration();
+
+  /// Starting with the last state, perform the following migration passes.
+  llvm::Optional<RC<MigrationState>> performSyntacticPasses(/*, Array of passes */);
+
+  /// Populate an array of replacements representing the difference between
+  /// the start state's text and the end state's text.
+  void getReplacements(SmallVectorImpl<Replacement> &Replacements) const;
+
+  /// Emit the output text of the final state in States to the path specified
+  /// by -emit-migrated-file-path in StartInvocation.MigratorOptions.
+  ///
+  /// Returns true if an attempt was made and failed.
+  bool emitMigratedFile() const;
+
+  /// Dump all of the migration states encountered so far to
+  /// StartInvocation.MigratorOptions.DumpMigrationStatesDir.
+  ///
+  /// Returns true if an attempt was made and failed.
+  bool dumpStates() const;
+
+  /// Get the options for the Migrator.
+  const MigratorOptions &getMigratorOptions() const;
+
+  /// Get the filename of the input given by this->StartInvocation.
+  const StringRef getInputFilename() const;
+};
+
+} // end namespace migrator
+} // end namespace swift
+
+#endif // SWIFT_MIGRATOR_MIGRATOR_H