add @_nodoc to @_exported import statements

Author: QuietMisdreavus

docs/ReferenceGuides/UnderscoredAttributes.md

@@ -489,6 +489,9 @@ marked with this attribute are treated as if they were given an underscored
 name, meaning they are still included in a symbol graph with a "minimum access
 level" of `internal` or lower.
 
+This attribute can also be attached to `@_exported import` statements to prevent
+symbols imported with this statement from appearing in symbol graphs.
+
 ## `@_nonEphemeral`
 
 Marks a function parameter that cannot accept a temporary pointer produced from

include/swift/AST/Import.h

@@ -84,6 +84,10 @@ enum class ImportFlags {
   /// concurrency.
   Preconcurrency = 0x20,
 
+  /// The module is being exported, but its contents should not appear in a
+  /// symbol graph.
+  NoDoc = 0x40,
+
   /// Used for DenseMap.
   Reserved = 0x80
 };

include/swift/AST/Module.h

@@ -951,7 +951,8 @@ inline SourceLoc extractNearestSourceLoc(const ModuleDecl *mod) {
 /// Collects modules that this module imports via `@_exported import`.
 void collectParsedExportedImports(const ModuleDecl *M,
                                   SmallPtrSetImpl<ModuleDecl *> &Imports,
-                                  llvm::SmallDenseMap<ModuleDecl *, SmallPtrSet<Decl *, 4>, 4> &QualifiedImports);
+                                  llvm::SmallDenseMap<ModuleDecl *, SmallPtrSet<Decl *, 4>, 4> &QualifiedImports,
+                                  bool DropNoDoc = false);
 
 } // end namespace swift
 

lib/AST/Module.cpp

@@ -794,12 +794,14 @@ bool ModuleDecl::shouldCollectDisplayDecls() const {
 
 void swift::collectParsedExportedImports(const ModuleDecl *M,
                                          SmallPtrSetImpl<ModuleDecl *> &Imports,
-                                         llvm::SmallDenseMap<ModuleDecl *, SmallPtrSet<Decl *, 4>, 4> &QualifiedImports) {
+                                         llvm::SmallDenseMap<ModuleDecl *, SmallPtrSet<Decl *, 4>, 4> &QualifiedImports,
+                                         bool DropNoDoc) {
   for (const FileUnit *file : M->getFiles()) {
     if (const SourceFile *source = dyn_cast<SourceFile>(file)) {
       if (source->hasImports()) {
         for (auto import : source->getImports()) {
           if (import.options.contains(ImportFlags::Exported) &&
+              !(DropNoDoc && import.options.contains(ImportFlags::NoDoc)) &&
               import.module.importedModule->shouldCollectDisplayDecls()) {
             auto *TheModule = import.module.importedModule;
 

lib/AST/TypeCheckRequests.cpp

@@ -1459,6 +1459,8 @@ void swift::simple_display(llvm::raw_ostream &out,
 
   if (import.options.contains(ImportFlags::Exported))
     out << " exported";
+  if (import.options.contains(ImportFlags::NoDoc))
+    out << " nodoc";
   if (import.options.contains(ImportFlags::Testable))
     out << " testable";
   if (import.options.contains(ImportFlags::ImplementationOnly))

lib/Sema/ImportResolution.cpp

@@ -530,6 +530,9 @@ UnboundImport::UnboundImport(ImportDecl *ID)
   if (ID->isExported())
     import.options |= ImportFlags::Exported;
 
+  if (ID->getAttrs().hasAttribute<NoDocAttr>())
+    import.options |= ImportFlags::NoDoc;
+
   if (ID->getAttrs().hasAttribute<TestableAttr>())
     import.options |= ImportFlags::Testable;
 
@@ -982,6 +985,11 @@ UnboundImport::UnboundImport(
       bystandingOptions.contains(ImportFlags::Exported))
     import.options |= ImportFlags::Exported;
 
+  // If both are @_nodoc, the cross-import is @_nodoc.
+  if (declaringOptions.contains(ImportFlags::NoDoc) &&
+      bystandingOptions.contains(ImportFlags::NoDoc))
+    import.options |= ImportFlags::NoDoc;
+
   // If either are implementation-only, the cross-import is
   // implementation-only.
   if (declaringOptions.contains(ImportFlags::ImplementationOnly) ||

lib/SymbolGraphGen/SymbolGraphGen.cpp

@@ -60,7 +60,8 @@ symbolgraphgen::emitSymbolGraphForModule(ModuleDecl *M,
 
   SmallPtrSet<ModuleDecl *, 4> ExportedImportedModules;
   llvm::SmallDenseMap<ModuleDecl *, SmallPtrSet<Decl *, 4>, 4> QualifiedImports;
-  swift::collectParsedExportedImports(M, ExportedImportedModules, QualifiedImports);
+  bool DropNoDoc = Options.MinimumAccessLevel > AccessLevel::Internal;
+  swift::collectParsedExportedImports(M, ExportedImportedModules, QualifiedImports, DropNoDoc);
 
   if (Options.PrintMessages)
     llvm::errs() << ModuleDecls.size()

test/SymbolGraph/Module/NoDocExportedImport.swift

@@ -0,0 +1,21 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend %S/Inputs/ExportedImport/A.swift -module-name A -emit-module -emit-module-path %t/A.swiftmodule
+// RUN: %target-swift-frontend %S/Inputs/ExportedImport/B.swift -module-name B -emit-module -emit-module-path %t/B.swiftmodule
+
+// RUN: %target-swift-frontend %s -module-name NoDocExportedImport -emit-module -emit-module-path /dev/null -I %t -emit-symbol-graph -emit-symbol-graph-dir %t/
+// RUN: %FileCheck %s --input-file %t/NoDocExportedImport.symbols.json --check-prefix PUBLIC
+// RUN: ls %t | %FileCheck %s --check-prefix FILES
+
+@_nodoc @_exported import A
+@_nodoc @_exported import struct B.StructOne
+
+// PUBLIC-NOT: InternalSymbolFromA
+// PUBLIC-NOT: StructTwo
+// PUBLIC-NOT: "precise":"s:1A11SymbolFromAV"
+// PUBLIC-NOT: "precise":"s:1B9StructOneV"
+
+// FIXME: Symbols from `@_exported import` do not get emitted when using swift-symbolgraph-extract
+// This is tracked by https://bugs.swift.org/browse/SR-15921.
+
+// FILES-NOT: [email protected]
+