[SourceKit] If diagnostics are 'stale' for a particular snapshot then ignore them and only return the syntactic parser diagnostics (#10388)

This makes sure that diagnostics returned for a particular state of source buffer are consistent and accurate.
rdar://32769873

Author: akyrtzi

test/SourceKit/CursorInfo/rdar_18677108-2.swift.response

@@ -5,7 +5,7 @@
     key.filepath: rdar_18677108-2-a.swift,
     key.severity: source.diagnostic.severity.error,
     key.description: "expected ')' in expression list",
-    key.diagnostic_stage: source.diagnostic.stage.swift.parse,
+    key.diagnostic_stage: source.diagnostic.stage.swift.sema,
     key.diagnostics: [
       {
         key.line: 5,
@@ -22,7 +22,7 @@
     key.filepath: rdar_18677108-2-a.swift,
     key.severity: source.diagnostic.severity.error,
     key.description: "expected '}' at end of brace statement",
-    key.diagnostic_stage: source.diagnostic.stage.swift.parse,
+    key.diagnostic_stage: source.diagnostic.stage.swift.sema,
     key.diagnostics: [
       {
         key.line: 4,
@@ -39,7 +39,7 @@
     key.filepath: rdar_18677108-2-a.swift,
     key.severity: source.diagnostic.severity.error,
     key.description: "expected '}' in class",
-    key.diagnostic_stage: source.diagnostic.stage.swift.parse,
+    key.diagnostic_stage: source.diagnostic.stage.swift.sema,
     key.diagnostics: [
       {
         key.line: 2,

test/SourceKit/Sema/sema_diag_after_edit_fixit.swift

@@ -4,7 +4,7 @@ let a = 0; let b = 0 }; unresolved
 // Test that offsets of diagnostic ranges and fixits get updated correctly after the edit request
 
 // RUN: %sourcekitd-test -req=open %s -- %s == -req=print-diags %s \
-// RUN:    == -req=edit -pos=2:1 -replace="_" -length=5 %s -print-raw-response \
+// RUN:    == -req=edit -pos=2:1 -replace="_" -length=5 %s == -req=print-diags %s \
 // RUN: | %FileCheck %s
 
 // CHECK:      key.line: 2,

test/SourceKit/Sema/sema_playground.swift.response

@@ -12,6 +12,6 @@
     key.filepath: sema_playground.swift,
     key.severity: source.diagnostic.severity.error,
     key.description: "expected numeric value following '$'",
-    key.diagnostic_stage: source.diagnostic.stage.swift.parse
+    key.diagnostic_stage: source.diagnostic.stage.swift.sema
   }
 ]

test/SourceKit/SyntaxMapData/diags.swift.response

@@ -6,7 +6,7 @@
     key.filepath: parse_error.swift,
     key.severity: source.diagnostic.severity.error,
     key.description: "expected '(' in argument list of function declaration",
-    key.diagnostic_stage: source.diagnostic.stage.swift.parse,
+    key.diagnostic_stage: source.diagnostic.stage.swift.sema,
     key.fixits: [
       {
         key.offset: 26,
@@ -37,7 +37,7 @@
     key.filepath: parse_error.swift,
     key.severity: source.diagnostic.severity.error,
     key.description: "expected '(' in argument list of function declaration",
-    key.diagnostic_stage: source.diagnostic.stage.swift.parse,
+    key.diagnostic_stage: source.diagnostic.stage.swift.sema,
     key.fixits: [
       {
         key.offset: 29,

tools/SourceKit/include/SourceKit/Core/Context.h

@@ -35,7 +35,8 @@ class Context {
 public:
   Context(StringRef RuntimeLibPath,
           llvm::function_ref<
-              std::unique_ptr<LangSupport>(Context &)> LangSupportFactoryFn);
+              std::unique_ptr<LangSupport>(Context &)> LangSupportFactoryFn,
+          bool shouldDispatchNotificationsOnMain = true);
   ~Context();
 
   StringRef getRuntimeLibPath() const { return RuntimeLibPath; }

tools/SourceKit/include/SourceKit/Core/NotificationCenter.h

@@ -14,6 +14,7 @@
 #define LLVM_SOURCEKIT_CORE_NOTIFICATIONCENTER_H
 
 #include "SourceKit/Core/LLVM.h"
+#include "llvm/Support/Mutex.h"
 #include <functional>
 #include <vector>
 
@@ -23,9 +24,14 @@ typedef std::function<void(StringRef DocumentName)>
     DocumentUpdateNotificationReceiver;
 
 class NotificationCenter {
+  bool DispatchToMain;
   std::vector<DocumentUpdateNotificationReceiver> DocUpdReceivers;
+  mutable llvm::sys::Mutex Mtx;
 
 public:
+  explicit NotificationCenter(bool dispatchToMain);
+  ~NotificationCenter();
+
   void addDocumentUpdateNotificationReceiver(
       DocumentUpdateNotificationReceiver Receiver);
 

tools/SourceKit/lib/Core/Context.cpp

@@ -18,8 +18,9 @@ using namespace SourceKit;
 
 SourceKit::Context::Context(StringRef RuntimeLibPath,
     llvm::function_ref<std::unique_ptr<LangSupport>(Context &)>
-    LangSupportFactoryFn) : RuntimeLibPath(RuntimeLibPath),
-    NotificationCtr(new NotificationCenter()) {
+    LangSupportFactoryFn,
+    bool shouldDispatchNotificationsOnMain) : RuntimeLibPath(RuntimeLibPath),
+    NotificationCtr(new NotificationCenter(shouldDispatchNotificationsOnMain)) {
   // Should be called last after everything is initialized.
   SwiftLang = LangSupportFactoryFn(*this);
 }

tools/SourceKit/lib/Core/NotificationCenter.cpp

@@ -15,20 +15,33 @@
 
 using namespace SourceKit;
 
+NotificationCenter::NotificationCenter(bool dispatchToMain)
+  : DispatchToMain(dispatchToMain) {
+}
+NotificationCenter::~NotificationCenter() {}
+
 void NotificationCenter::addDocumentUpdateNotificationReceiver(
     DocumentUpdateNotificationReceiver Receiver) {
 
-  WorkQueue::dispatchOnMain([this, Receiver]{
-    DocUpdReceivers.push_back(Receiver);
-  });
+  llvm::sys::ScopedLock L(Mtx);
+  DocUpdReceivers.push_back(Receiver);
 }
 
 void NotificationCenter::postDocumentUpdateNotification(
     StringRef DocumentName) const {
-  
-  std::string DocName = DocumentName;
-  WorkQueue::dispatchOnMain([this, DocName]{
-    for (auto &Fn : DocUpdReceivers)
-      Fn(DocName);
-  });
+
+  std::vector<DocumentUpdateNotificationReceiver> recvs;
+  {
+    llvm::sys::ScopedLock L(Mtx);
+    recvs = DocUpdReceivers;
+  }  
+  std::string docName = DocumentName;
+  auto sendNote = [recvs, docName]{
+    for (auto &Fn : recvs)
+      Fn(docName);
+  };
+  if (DispatchToMain)
+    WorkQueue::dispatchOnMain(sendNote);
+  else
+    sendNote();
 }