[SourceKit] Add "Active Regions" request

`source.request.activeregions` is a new request that reports all
`#if`, `#else` and `#elseif` decls in the response with an `is_active` flag.
This is mainly useful for a client to know which branches are active,
but for completeness sake, the active decls are also reported.

Note: it only reports the positions of the decls, not the entire ranges.
It's up to clients to map this to the syntactic structure of a tree.
Reporting the ranges of the decls could be confusing in the case
of nested `#if`s, where the ranges can overlap.

Author: louisdh

test/SourceKit/ActiveRegions/nested.swift

@@ -0,0 +1,47 @@
+#if FLAG_1
+class Foo {
+    #if FLAG_2
+    func debugOnly() {
+        
+    }
+    #endif
+}
+#elseif FLAG_3
+class GracefulFallback {
+    
+}
+#else
+class Fallback {
+    
+}
+#endif
+
+// RUN: %sourcekitd-test -req=active-regions %s -- -D FLAG_1 -module-name active_regions %s | %FileCheck -check-prefix=CHECK1 %s
+// CHECK1: START IF CONFIGS
+// CHECK1-NEXT: 1:1 - active
+// CHECK1-NEXT: 3:5 - inactive
+// CHECK1-NEXT: 9:1 - inactive
+// CHECK1-NEXT: 13:1 - inactive
+// CHECK1-NEXT: END IF CONFIGS
+
+// RUN: %sourcekitd-test -req=active-regions %s -- -D FLAG_2 -module-name active_regions %s | %FileCheck -check-prefix=CHECK2 %s
+// CHECK2: START IF CONFIGS
+// CHECK2-NEXT: 1:1 - inactive
+// CHECK2-NEXT: 9:1 - inactive
+// CHECK2-NEXT: 13:1 - active
+// CHECK2-NEXT: END IF CONFIGS
+
+// RUN: %sourcekitd-test -req=active-regions %s -- -D FLAG_1 -D FLAG_2 -module-name active_regions %s | %FileCheck -check-prefix=CHECK3 %s
+// CHECK3: START IF CONFIGS
+// CHECK3-NEXT: 1:1 - active
+// CHECK3-NEXT: 3:5 - active
+// CHECK3-NEXT: 9:1 - inactive
+// CHECK3-NEXT: 13:1 - inactive
+// CHECK3-NEXT: END IF CONFIGS
+
+// RUN: %sourcekitd-test -req=active-regions %s -- -D FLAG_3 -module-name active_regions %s | %FileCheck -check-prefix=CHECK4 %s
+// CHECK4: START IF CONFIGS
+// CHECK4-NEXT: 1:1 - inactive
+// CHECK4-NEXT: 9:1 - active
+// CHECK4-NEXT: 13:1 - inactive
+// CHECK4-NEXT: END IF CONFIGS

test/SourceKit/ActiveRegions/syntactically_invalid.swift

@@ -0,0 +1,12 @@
+#if FOO > 10
+class Foo {
+}
+#else
+class Fallback {
+}
+#endif
+// RUN: %sourcekitd-test -req=active-regions %s -- -module-name active_regions %s | %FileCheck -check-prefix=CHECK1 %s
+// CHECK1: START IF CONFIGS
+// CHECK1-NEXT: 1:1 - inactive
+// CHECK1-NEXT: 4:1 - active
+// CHECK1-NEXT: END IF CONFIGS

test/SourceKit/ActiveRegions/unterminated.swift

@@ -0,0 +1,12 @@
+#if FLAG_1
+class Foo {
+}
+#else
+class Fallback {
+}
+
+// RUN: %sourcekitd-test -req=active-regions %s -- -D FLAG_1 -module-name active_regions %s | %FileCheck -check-prefix=CHECK1 %s
+// CHECK1: START IF CONFIGS
+// CHECK1-NEXT: 1:1 - active
+// CHECK1-NEXT: 4:1 - inactive
+// CHECK1-NEXT: END IF CONFIGS

tools/SourceKit/include/SourceKit/Core/LangSupport.h

@@ -648,6 +648,20 @@ struct RelatedIdentsInfo {
   ArrayRef<std::pair<unsigned, unsigned>> Ranges;
 };
 
+/// Represent one branch of an if config.
+/// Either `#if`, `#else` or `#elseif`.
+struct IfConfigInfo {
+  unsigned Offset;
+  bool IsActive;
+
+  IfConfigInfo(unsigned Offset, bool IsActive)
+      : Offset(Offset), IsActive(IsActive) {}
+};
+
+struct ActiveRegionsInfo {
+  ArrayRef<IfConfigInfo> Configs;
+};
+
 /// Filled out by LangSupport::findInterfaceDocument().
 struct InterfaceDocInfo {
   /// Non-empty if a generated interface editor document has previously been
@@ -993,6 +1007,12 @@ class LangSupport {
       std::function<void(const RequestResult<RelatedIdentsInfo> &)>
           Receiver) = 0;
 
+  virtual void findActiveRegionsInFile(
+      StringRef Filename, ArrayRef<const char *> Args,
+      SourceKitCancellationToken CancellationToken,
+      std::function<void(const RequestResult<ActiveRegionsInfo> &)>
+          Receiver) = 0;
+
   virtual llvm::Optional<std::pair<unsigned, unsigned>>
       findUSRRange(StringRef DocumentName, StringRef USR) = 0;
 

tools/SourceKit/lib/SwiftLang/SwiftLangSupport.h

@@ -672,6 +672,12 @@ class SwiftLangSupport : public LangSupport {
       std::function<void(const RequestResult<RelatedIdentsInfo> &)> Receiver)
       override;
 
+  void findActiveRegionsInFile(
+      StringRef Filename, ArrayRef<const char *> Args,
+      SourceKitCancellationToken CancellationToken,
+      std::function<void(const RequestResult<ActiveRegionsInfo> &)> Receiver)
+      override;
+
   void syntacticRename(llvm::MemoryBuffer *InputBuf,
                        ArrayRef<RenameLocations> RenameLocations,
                        ArrayRef<const char*> Args,

tools/SourceKit/lib/SwiftLang/SwiftSourceDocInfo.cpp

@@ -2572,6 +2572,101 @@ void SwiftLangSupport::findRelatedIdentifiersInFile(
                           llvm::vfs::getRealFileSystem());
 }
 
+//===----------------------------------------------------------------------===//
+// SwiftLangSupport::findActiveRegionsInFile
+//===----------------------------------------------------------------------===//
+
+namespace {
+class IfConfigScanner : public SourceEntityWalker {
+  SmallVectorImpl<IfConfigInfo> &Infos;
+  SourceManager &SourceMgr;
+  unsigned BufferID = -1;
+  bool Cancelled = false;
+
+public:
+  explicit IfConfigScanner(SourceFile &SrcFile, unsigned BufferID,
+                           SmallVectorImpl<IfConfigInfo> &Infos)
+      : Infos(Infos), SourceMgr(SrcFile.getASTContext().SourceMgr),
+        BufferID(BufferID) {}
+
+private:
+  bool walkToDeclPre(Decl *D, CharSourceRange Range) override {
+    if (Cancelled)
+      return false;
+
+    if (auto *IfDecl = dyn_cast<IfConfigDecl>(D)) {
+      for (auto &Clause : IfDecl->getClauses()) {
+        unsigned Offset = SourceMgr.getLocOffsetInBuffer(Clause.Loc, BufferID);
+        Infos.emplace_back(Offset, Clause.isActive);
+      }
+    }
+
+    return true;
+  }
+};
+
+} // end anonymous namespace
+
+void SwiftLangSupport::findActiveRegionsInFile(
+    StringRef InputFile, ArrayRef<const char *> Args,
+    SourceKitCancellationToken CancellationToken,
+    std::function<void(const RequestResult<ActiveRegionsInfo> &)> Receiver) {
+
+  std::string Error;
+  SwiftInvocationRef Invok =
+      ASTMgr->getTypecheckInvocation(Args, InputFile, Error);
+  if (!Invok) {
+    LOG_WARN_FUNC("failed to create an ASTInvocation: " << Error);
+    Receiver(RequestResult<ActiveRegionsInfo>::fromError(Error));
+    return;
+  }
+
+  class IfConfigConsumer : public SwiftASTConsumer {
+    std::function<void(const RequestResult<ActiveRegionsInfo> &)> Receiver;
+    SwiftInvocationRef Invok;
+
+  public:
+    IfConfigConsumer(
+        std::function<void(const RequestResult<ActiveRegionsInfo> &)> Receiver,
+        SwiftInvocationRef Invok)
+        : Receiver(std::move(Receiver)), Invok(Invok) {}
+
+    void handlePrimaryAST(ASTUnitRef AstUnit) override {
+      auto &SrcFile = AstUnit->getPrimarySourceFile();
+      SmallVector<IfConfigInfo> Configs;
+      auto BufferID = SrcFile.getBufferID();
+      if (!BufferID)
+        return;
+      IfConfigScanner Scanner(SrcFile, *BufferID, Configs);
+      Scanner.walk(SrcFile);
+
+      // Sort by offset so nested decls are reported
+      // in source order (not tree order).
+      llvm::sort(Configs,
+                 [](const IfConfigInfo &LHS, const IfConfigInfo &RHS) -> bool {
+                   return LHS.Offset < RHS.Offset;
+                 });
+      ActiveRegionsInfo Info;
+      Info.Configs = Configs;
+      Receiver(RequestResult<ActiveRegionsInfo>::fromResult(Info));
+    }
+
+    void cancelled() override {
+      Receiver(RequestResult<ActiveRegionsInfo>::cancelled());
+    }
+
+    void failed(StringRef Error) override {
+      LOG_WARN_FUNC("inactive ranges failed: " << Error);
+      Receiver(RequestResult<ActiveRegionsInfo>::fromError(Error));
+    }
+  };
+
+  auto Consumer = std::make_shared<IfConfigConsumer>(Receiver, Invok);
+  ASTMgr->processASTAsync(Invok, std::move(Consumer),
+                          /*OncePerASTToken=*/nullptr, CancellationToken,
+                          llvm::vfs::getRealFileSystem());
+}
+
 //===----------------------------------------------------------------------===//
 // SwiftLangSupport::semanticRefactoring
 //===----------------------------------------------------------------------===//

tools/SourceKit/tools/sourcekitd-test/TestOptions.cpp

@@ -120,6 +120,7 @@ bool TestOptions::parseArgs(llvm::ArrayRef<const char *> Args) {
         .Case("conformingmethods", SourceKitRequest::ConformingMethodList)
         .Case("cursor", SourceKitRequest::CursorInfo)
         .Case("related-idents", SourceKitRequest::RelatedIdents)
+        .Case("active-regions", SourceKitRequest::ActiveRegions)
         .Case("syntax-map", SourceKitRequest::SyntaxMap)
         .Case("structure", SourceKitRequest::Structure)
         .Case("format", SourceKitRequest::Format)

tools/SourceKit/tools/sourcekitd-test/TestOptions.h

@@ -35,6 +35,7 @@ enum class SourceKitRequest {
   CodeCompleteSetPopularAPI,
   TypeContextInfo,
   ConformingMethodList,
+  ActiveRegions,
   CursorInfo,
   RangeInfo,
   RelatedIdents,

tools/SourceKit/tools/sourcekitd-test/sourcekitd-test.cpp

@@ -76,6 +76,9 @@ static void printSemanticInfo();
 static void printRelatedIdents(sourcekitd_variant_t Info, StringRef Filename,
                                const llvm::StringMap<TestOptions::VFSFile> &VFSFiles,
                                llvm::raw_ostream &OS);
+static void printActiveRegions(sourcekitd_variant_t Info, StringRef Filename,
+                               const llvm::StringMap<TestOptions::VFSFile> &VFSFiles,
+                               llvm::raw_ostream &OS);
 static void printFoundInterface(sourcekitd_variant_t Info,
                                 llvm::raw_ostream &OS);
 static void printFoundUSR(sourcekitd_variant_t Info,
@@ -879,6 +882,10 @@ static int handleTestInvocation(TestOptions Opts, TestOptions &InitOpts) {
     sourcekitd_request_dictionary_set_uid(Req, KeyRequest, RequestRelatedIdents);
     sourcekitd_request_dictionary_set_int64(Req, KeyOffset, ByteOffset);
     break;
+      
+  case SourceKitRequest::ActiveRegions:
+    sourcekitd_request_dictionary_set_uid(Req, KeyRequest, RequestActiveRegions);
+    break;
 
   case SourceKitRequest::SyntaxMap:
     sourcekitd_request_dictionary_set_uid(Req, KeyRequest, RequestEditorOpen);
@@ -1339,6 +1346,10 @@ static bool handleResponse(sourcekitd_response_t Resp, const TestOptions &Opts,
       printRelatedIdents(Info, SourceFile, Opts.VFSFiles, llvm::outs());
       break;
 
+    case SourceKitRequest::ActiveRegions:
+      printActiveRegions(Info, SourceFile, Opts.VFSFiles, llvm::outs());
+      break;
+
     case SourceKitRequest::CursorInfo:
       printCursorInfo(Info, SourceFile, Opts.VFSFiles, llvm::outs());
       break;
@@ -2336,6 +2347,22 @@ static void printRelatedIdents(sourcekitd_variant_t Info, StringRef Filename,
   OS << "END RANGES\n";
 }
 
+static void printActiveRegions(sourcekitd_variant_t Info, StringRef Filename,
+                               const llvm::StringMap<TestOptions::VFSFile> &VFSFiles,
+                               llvm::raw_ostream &OS) {
+  OS << "START IF CONFIGS\n";
+  sourcekitd_variant_t Res =
+      sourcekitd_variant_dictionary_get_value(Info, KeyResults);
+  for (unsigned i=0, e = sourcekitd_variant_array_get_count(Res); i != e; ++i) {
+    sourcekitd_variant_t IfConfig = sourcekitd_variant_array_get_value(Res, i);
+    int64_t Offset = sourcekitd_variant_dictionary_get_int64(IfConfig, KeyOffset);
+    auto LineCol = resolveToLineCol(Offset, Filename, VFSFiles);
+    bool IsActive = sourcekitd_variant_dictionary_get_bool(IfConfig, KeyIsActive);
+    OS << LineCol.first << ':' << LineCol.second << " - " << (IsActive ? "active" : "inactive") << '\n';
+  }
+  OS << "END IF CONFIGS\n";
+}
+
 static void prepareDemangleRequest(sourcekitd_object_t Req,
                                    const TestOptions &Opts) {
   sourcekitd_request_dictionary_set_uid(Req, KeyRequest, RequestDemangle);

tools/SourceKit/tools/sourcekitd/lib/Service/Requests.cpp

@@ -210,6 +210,10 @@ static void findRelatedIdents(StringRef Filename, int64_t Offset,
                               SourceKitCancellationToken CancellationToken,
                               ResponseReceiver Rec);
 
+static void findActiveRegions(StringRef Filename, ArrayRef<const char *> Args,
+                              SourceKitCancellationToken CancellationToken,
+                              ResponseReceiver Rec);
+
 static sourcekitd_response_t
 codeComplete(llvm::MemoryBuffer *InputBuf, int64_t Offset,
              Optional<RequestDict> optionsDict, ArrayRef<const char *> Args,
@@ -1682,6 +1686,25 @@ handleRequestRelatedIdents(const RequestDict &Req,
   });
 }
 
+static void
+handleRequestActiveRegions(const RequestDict &Req,
+                           SourceKitCancellationToken CancellationToken,
+                           ResponseReceiver Rec) {
+  if (checkVFSNotSupported(Req, Rec))
+    return;
+
+  handleSemanticRequest(Req, Rec, [Req, CancellationToken, Rec]() {
+    auto SourceFile = getSourceFileNameForRequestOrEmitError(Req, Rec);
+    if (!SourceFile)
+      return;
+    SmallVector<const char *> Args;
+    if (getCompilerArgumentsForRequestOrEmitError(Req, Args, Rec))
+      return;
+
+    return findActiveRegions(*SourceFile, Args, CancellationToken, Rec);
+  });
+}
+
 static void
 handleRequestDiagnostics(const RequestDict &Req,
                          SourceKitCancellationToken CancellationToken,
@@ -1805,6 +1828,7 @@ void handleRequestImpl(sourcekitd_object_t ReqObj,
                  handleRequestFindLocalRenameRanges)
   HANDLE_REQUEST(RequestNameTranslation, handleRequestNameTranslation)
   HANDLE_REQUEST(RequestRelatedIdents, handleRequestRelatedIdents)
+  HANDLE_REQUEST(RequestActiveRegions, handleRequestActiveRegions)
   HANDLE_REQUEST(RequestDiagnostics, handleRequestDiagnostics)
 
   {
@@ -2576,6 +2600,38 @@ static void findRelatedIdents(StringRef Filename, int64_t Offset,
       });
 }
 
+//===----------------------------------------------------------------------===//
+// FindActiveRegions
+//===----------------------------------------------------------------------===//
+
+static void findActiveRegions(StringRef Filename, ArrayRef<const char *> Args,
+                              SourceKitCancellationToken CancellationToken,
+                              ResponseReceiver Rec) {
+  LangSupport &Lang = getGlobalContext().getSwiftLangSupport();
+
+  Lang.findActiveRegionsInFile(
+      Filename, Args, CancellationToken,
+      [Rec](const RequestResult<ActiveRegionsInfo> &Result) {
+        if (Result.isCancelled())
+          return Rec(createErrorRequestCancelled());
+        if (Result.isError())
+          return Rec(createErrorRequestFailed(Result.getError()));
+
+        const ActiveRegionsInfo &Info = Result.value();
+
+        ResponseBuilder RespBuilder;
+        auto Arr = RespBuilder.getDictionary().setArray(KeyResults);
+        for (auto Config : Info.Configs) {
+          auto Elem = Arr.appendDictionary();
+          Elem.set(KeyOffset, Config.Offset);
+          if (Config.IsActive)
+            Elem.setBool(KeyIsActive, true);
+        }
+
+        Rec(RespBuilder.createResponse());
+      });
+}
+
 //===----------------------------------------------------------------------===//
 // CodeComplete
 //===----------------------------------------------------------------------===//

utils/gyb_sourcekit_support/UIDs.py

@@ -83,6 +83,7 @@ def __init__(self, internal_name, external_name):
     KEY('BodyLength', 'key.bodylength'),
     KEY('DocOffset', 'key.docoffset'),
     KEY('DocLength', 'key.doclength'),
+    KEY('IsActive', 'key.is_active'),
     KEY('IsLocal', 'key.is_local'),
     KEY('InheritedTypes', 'key.inheritedtypes'),
     KEY('Attributes', 'key.attributes'),
@@ -224,6 +225,7 @@ def __init__(self, internal_name, external_name):
     REQUEST('CodeCompleteSetCustom', 'source.request.codecomplete.setcustom'),
     REQUEST('TypeContextInfo', 'source.request.typecontextinfo'),
     REQUEST('ConformingMethodList', 'source.request.conformingmethods'),
+    REQUEST('ActiveRegions', 'source.request.activeregions'),
     REQUEST('CursorInfo', 'source.request.cursorinfo'),
     REQUEST('RangeInfo', 'source.request.rangeinfo'),
     REQUEST('RelatedIdents', 'source.request.relatedidents'),