[Diagnostics] Updated (experimental) diagnostic printing style (#30027)

* [Diagnostics] Experimental diagnostic printing updates

This new style directly annotates small snippets of code with
error messages, highlights and fix-its. It also uses color more
effectively to highlight important segments.

* [Diagnostics] Stage educational notes and experimental formatting behind separate frontend flags

educational notes -> -enable-educational-notes
formatting -> -enable-experimental-diagnostic-formatting

* [Diagnostics] Refactor expensive line lookups in diag formatting

* [Diagnostics] Refactor some PrintingDiagnosticConsumer code into a flush method

* [Diag-Experimental-Formatting] Custom formatting for Xcode editor placeholders

* [Diag-Experimental-Formatting] Better and more consistent textual description of fix its

* [Diags-Experimental-Formatting] Handle lines with tab characters correctly when rendering highlights and messages

Tabs are converted to 2 spaces for display purposes.

* [Diag-Experimental-Formatting] Refactor byte-to-column mapping for efficiency

* [Diag-Experimental-Formatting] Fix line number indent calculation

* [Diag-Experimental-Formatting] Include indicators of insertions and deletions in the highlight line

Inserts are underlined by green '+' chars, deletions by red '-' chars.

* [Diag-Experimental-Formatting] Change color of indicator arrow for non-ASCII anchored messages
* [Diag-experimental-formatting] Make tests less sensitive to line numbering

* [Diag-Experimental-Formatting] Update tests to allow windows path separators

* [Diag-Experimental-Formatting] Bug fixes for the integrated REPL

Author: owenv

include/swift/AST/DiagnosticConsumer.h

@@ -126,6 +126,9 @@ class DiagnosticConsumer {
   /// \returns true if an error occurred while finishing-up.
   virtual bool finishProcessing() { return false; }
 
+  /// Flush any in-flight diagnostics.
+  virtual void flush() {}
+
   /// In batch mode, any error causes failure for all primary files, but
   /// anyone consulting .dia files will only see an error for a particular
   /// primary in that primary's serialized diagnostics file. For other

include/swift/AST/DiagnosticEngine.h

@@ -676,8 +676,8 @@ namespace swift {
     /// Print diagnostic names after their messages
     bool printDiagnosticNames = false;
 
-    /// Use descriptive diagnostic style when available.
-    bool useDescriptiveDiagnostics = false;
+    /// Use educational notes when available.
+    bool useEducationalNotes = false;
 
     /// Path to diagnostic documentation directory.
     std::string diagnosticDocumentationPath = "";
@@ -705,6 +705,11 @@ namespace swift {
       return state.getShowDiagnosticsAfterFatalError();
     }
 
+    void flushConsumers() {
+      for (auto consumer : Consumers)
+        consumer->flush();
+    }
+
     /// Whether to skip emitting warnings
     void setSuppressWarnings(bool val) { state.setSuppressWarnings(val); }
     bool getSuppressWarnings() const {
@@ -725,12 +730,8 @@ namespace swift {
       return printDiagnosticNames;
     }
 
-    void setUseDescriptiveDiagnostics(bool val) {
-       useDescriptiveDiagnostics = val;
-    }
-    bool getUseDescriptiveDiagnostics() const {
-      return useDescriptiveDiagnostics;
-    }
+    void setUseEducationalNotes(bool val) { useEducationalNotes = val; }
+    bool getUseEducationalNotes() const { return useEducationalNotes; }
 
     void setDiagnosticDocumentationPath(std::string path) {
       diagnosticDocumentationPath = path;

include/swift/Basic/DiagnosticOptions.h

@@ -55,9 +55,13 @@ class DiagnosticOptions {
   // When printing diagnostics, include the diagnostic name at the end
   bool PrintDiagnosticNames = false;
 
-  /// If set to true, produce more descriptive diagnostic output if available.
-  /// Descriptive diagnostic output is not intended to be machine-readable.
-  bool EnableDescriptiveDiagnostics = false;
+  /// If set to true, display educational note content to the user if available.
+  /// Educational notes are documentation which supplement diagnostics.
+  bool EnableEducationalNotes = false;
+
+  // If set to true, use the more descriptive experimental formatting style for
+  // diagnostics.
+  bool EnableExperimentalFormatting = false;
 
   std::string DiagnosticDocumentationPath = "";
 

include/swift/Basic/SourceManager.h

@@ -256,6 +256,8 @@ class SourceManager {
                                SourceLoc();
   }
 
+  std::string getLineString(unsigned BufferID, unsigned LineNumber);
+
   SourceLoc getLocFromExternalSource(StringRef Path, unsigned Line, unsigned Col);
 private:
   const VirtualFile *getVirtualFile(SourceLoc Loc) const;

include/swift/Frontend/PrintingDiagnosticConsumer.h

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 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
@@ -25,24 +25,39 @@
 #include "llvm/Support/Process.h"
 
 namespace swift {
+class AnnotatedSourceSnippet;
 
 /// Diagnostic consumer that displays diagnostics to standard error.
 class PrintingDiagnosticConsumer : public DiagnosticConsumer {
   llvm::raw_ostream &Stream;
   bool ForceColors = false;
   bool DidErrorOccur = false;
+  bool ExperimentalFormattingEnabled = false;
+  // The current snippet used to display an error/warning/remark and the notes
+  // implicitly associated with it. Uses `std::unique_ptr` so that
+  // `AnnotatedSourceSnippet` can be forward declared.
+  std::unique_ptr<AnnotatedSourceSnippet> currentSnippet;
+
 public:
-  PrintingDiagnosticConsumer(llvm::raw_ostream &stream = llvm::errs()) :
-    Stream(stream) { }
+  PrintingDiagnosticConsumer(llvm::raw_ostream &stream = llvm::errs());
+  ~PrintingDiagnosticConsumer();
 
   virtual void handleDiagnostic(SourceManager &SM,
                                 const DiagnosticInfo &Info) override;
 
+  virtual bool finishProcessing() override;
+
+  void flush(bool includeTrailingBreak);
+
+  virtual void flush() override { flush(false); }
+
   void forceColors() {
     ForceColors = true;
     llvm::sys::Process::UseANSIEscapeCodes(true);
   }
 
+  void enableExperimentalFormatting() { ExperimentalFormattingEnabled = true; }
+
   bool didErrorOccur() {
     return DidErrorOccur;
   }

include/swift/Option/FrontendOptions.td

@@ -131,8 +131,12 @@ def enable_cross_import_overlays : Flag<["-"], "enable-cross-import-overlays">,
 def disable_cross_import_overlays : Flag<["-"], "disable-cross-import-overlays">,
   HelpText<"Do not automatically import declared cross-import overlays.">;
 
-def enable_descriptive_diagnostics : Flag<["-"], "enable-descriptive-diagnostics">,
-  HelpText<"Show descriptive diagnostic information, if available.">;
+def enable_educational_notes : Flag<["-"], "enable-educational-notes">,
+  HelpText<"Show educational notes, if available.">;
+  
+def enable_experimental_diagnostic_formatting :
+  Flag<["-"], "enable-experimental-diagnostic-formatting">,
+  HelpText<"Enable experimental diagnostic formatting features.">;
 
 def diagnostic_documentation_path
   : Separate<["-"], "diagnostic-documentation-path">, MetaVarName<"<path>">,

lib/AST/DiagnosticEngine.cpp

@@ -984,7 +984,7 @@ void DiagnosticEngine::emitDiagnostic(const Diagnostic &diagnostic) {
     info->ChildDiagnosticInfo = childInfoPtrs;
 
     SmallVector<std::string, 1> educationalNotePaths;
-    if (useDescriptiveDiagnostics) {
+    if (useEducationalNotes) {
       auto associatedNotes = educationalNotes[(uint32_t)diagnostic.getID()];
       while (associatedNotes && *associatedNotes) {
         SmallString<128> notePath(getDiagnosticDocumentationPath());

lib/Frontend/CompilerInvocation.cpp

@@ -819,8 +819,9 @@ static bool ParseDiagnosticArgs(DiagnosticOptions &Opts, ArgList &Args,
   Opts.SuppressWarnings |= Args.hasArg(OPT_suppress_warnings);
   Opts.WarningsAsErrors |= Args.hasArg(OPT_warnings_as_errors);
   Opts.PrintDiagnosticNames |= Args.hasArg(OPT_debug_diagnostic_names);
-  Opts.EnableDescriptiveDiagnostics |=
-      Args.hasArg(OPT_enable_descriptive_diagnostics);
+  Opts.EnableEducationalNotes |= Args.hasArg(OPT_enable_educational_notes);
+  Opts.EnableExperimentalFormatting |=
+      Args.hasArg(OPT_enable_experimental_diagnostic_formatting);
   if (Arg *A = Args.getLastArg(OPT_diagnostic_documentation_path)) {
     Opts.DiagnosticDocumentationPath = A->getValue();
   }

lib/Frontend/Frontend.cpp

@@ -406,8 +406,8 @@ void CompilerInstance::setUpDiagnosticOptions() {
   if (Invocation.getDiagnosticOptions().PrintDiagnosticNames) {
     Diagnostics.setPrintDiagnosticNames(true);
   }
-  if (Invocation.getDiagnosticOptions().EnableDescriptiveDiagnostics) {
-    Diagnostics.setUseDescriptiveDiagnostics(true);
+  if (Invocation.getDiagnosticOptions().EnableEducationalNotes) {
+    Diagnostics.setUseEducationalNotes(true);
   }
   Diagnostics.setDiagnosticDocumentationPath(
       Invocation.getDiagnosticOptions().DiagnosticDocumentationPath);