Merge pull request swiftlang#38782 from ahoppen/pr/sourcekit-cancellation

[SourceKit] Support cancellation of requests while an AST is being built

Author: ahoppen

include/swift/Basic/LangOptions.h

@@ -595,6 +595,12 @@ namespace swift {
     /// than this many seconds.
     unsigned ExpressionTimeoutThreshold = 600;
 
+    /// If the shared pointer is not a \c nullptr and the pointee is \c true,
+    /// typechecking should be aborted at the next possible opportunity.
+    /// This is used by SourceKit to cancel requests for which the result is no
+    /// longer of interest.
+    std::shared_ptr<std::atomic<bool>> CancellationFlag = nullptr;
+
     /// If non-zero, abort the switch statement exhaustiveness checker if
     /// the Space::minus function is called more than this many times.
     ///

include/swift/Sema/ConstraintSystem.h

@@ -5113,6 +5113,10 @@ class ConstraintSystem {
     if (isExpressionAlreadyTooComplex)
       return true;
 
+    auto CancellationFlag = getASTContext().TypeCheckerOpts.CancellationFlag;
+    if (CancellationFlag && CancellationFlag->load(std::memory_order_relaxed))
+      return true;
+
     auto used = getASTContext().getSolverMemory() + solutionMemory;
     MaxMemory = std::max(used, MaxMemory);
     auto threshold = getASTContext().TypeCheckerOpts.SolverMemoryThreshold;

test/SourceKit/Misc/stats.swift

@@ -46,8 +46,8 @@ func foo() {}
 // SEMA_3: 1 {{.*}} source.statistic.num-ast-builds
 // SEMA_3: 1 {{.*}} source.statistic.num-asts-in-memory
 // SEMA_3: 1 {{.*}} source.statistic.max-asts-in-memory
-// SEMA_3: 0 {{.*}} source.statistic.num-ast-cache-hits
-// SEMA_3: 1 {{.*}} source.statistic.num-ast-snaphost-uses
+// SEMA_3: 1 {{.*}} source.statistic.num-ast-cache-hits
+// SEMA_3: 0 {{.*}} source.statistic.num-ast-snaphost-uses
 
 // RUN: %sourcekitd-test -req=sema %s -- -Xfrontend -disable-implicit-concurrency-module-import  %s == -req=related-idents -pos=1:6 %s -- -Xfrontend -disable-implicit-concurrency-module-import  %s == -req=stats | %FileCheck %s -check-prefix=SEMA_4
 
@@ -58,3 +58,14 @@ func foo() {}
 // SEMA_4: 1 {{.*}} source.statistic.max-asts-in-memory
 // SEMA_4: 1 {{.*}} source.statistic.num-ast-cache-hits
 // SEMA_4: 0 {{.*}} source.statistic.num-ast-snaphost-uses
+
+// Test that we can have two files open and don't need to rebuild an AST when doing the cursor info request on '%s' after opening '10bytes.swift'
+// RUN: %sourcekitd-test \
+// RUN: -req=sema %s -- -Xfrontend -disable-implicit-concurrency-module-import  %s == \
+// RUN: -req=sema %S/Inputs/10bytes.swift -- -Xfrontend -disable-implicit-concurrency-module-import %S/Inputs/10bytes.swift == \
+// RUN: -req=cursor -pos=1:6 %s -- -Xfrontend -disable-implicit-concurrency-module-import  %s == \
+// RUN: -req=stats | %FileCheck %s -check-prefix=OPEN_TWO_FILES
+
+// OPEN_TWO_FILES: 2 {{.*}} source.statistic.num-ast-builds
+// OPEN_TWO_FILES: 2 {{.*}} source.statistic.num-asts-in-memory
+// OPEN_TWO_FILES: 2 {{.*}} source.statistic.max-asts-in-memory