introduce a @_documentation(...) attribute to influence SymbolGraphGen (#60242)

* add @_documentation(...) attribute to influence SymbolGraphGen

rdar://79049241

Author: QuietMisdreavus

docs/ReferenceGuides/UnderscoredAttributes.md

@@ -121,6 +121,27 @@ extension Text {
 }
 ```
 
+## `@_documentation(metadata: ...)`
+
+Adds "documentation metadata" to the symbol. The identifier in the attribute is
+added to the symbol graph in the `"metadata"` field of the symbol. This can be
+used to add an arbitrary grouping or other indicator to symbols for use in
+documentation.
+
+## `@_documentation(visibility: ...)`
+
+Forces the symbol to be treated as the given access level when checking
+visibility. This can be used to, for example, force a symbol with an underscored
+name to appear in `public` symbol graphs, or treat an otherwise-`public` symbol
+as being `internal` or `private` for the purposes of documentation, to hide it
+from `public` docs.
+
+This can also be applied to `@_exported import` statements to only include the
+imported symbols in symbol graphs with the given minimum access level. For
+example, applying `@_documentation(visibility: internal)` to an `@_exported
+import` statement will hide the imported symbols from `public` symbol graphs and
+documentation, but show them on `internal` symbol graphs and documentation.
+
 ## `@_dynamicReplacement(for: targetFunc(label:))`
 
 Marks a function as the dynamic replacement for another `dynamic` function.

include/swift/AST/Attr.def

@@ -773,6 +773,11 @@ SIMPLE_DECL_ATTR(_spiOnly, SPIOnly,
   ABIStableToAdd | ABIStableToRemove | APIStableToAdd | APIStableToRemove,
   135)
 
+DECL_ATTR(_documentation, Documentation,
+  OnAnyDecl | UserInaccessible |
+  APIBreakingToAdd | APIStableToRemove | ABIStableToAdd | ABIStableToRemove,
+  136)
+
 // If you're adding a new underscored attribute here, please document it in
 // docs/ReferenceGuides/UnderscoredAttributes.md.
 

include/swift/AST/Attr.h

@@ -2244,6 +2244,27 @@ class ExposeAttr : public DeclAttribute {
   }
 };
 
+/// The `@_documentation(...)` attribute, used to override a symbol's visibility
+/// in symbol graphs, and/or adding arbitrary metadata to it.
+class DocumentationAttr: public DeclAttribute {
+public:
+  DocumentationAttr(SourceLoc AtLoc, SourceRange Range,
+                    StringRef Metadata, Optional<AccessLevel> Visibility,
+                    bool Implicit)
+  : DeclAttribute(DAK_Documentation, AtLoc, Range, Implicit),
+    Metadata(Metadata), Visibility(Visibility) {}
+
+  DocumentationAttr(StringRef Metadata, Optional<AccessLevel> Visibility, bool Implicit)
+  : DocumentationAttr(SourceLoc(), SourceRange(), Metadata, Visibility, Implicit) {}
+
+  const StringRef Metadata;
+  const Optional<AccessLevel> Visibility;
+
+  static bool classof(const DeclAttribute *DA) {
+    return DA->getKind() == DAK_Documentation;
+  }
+};
+
 /// Attributes that may be applied to declarations.
 class DeclAttributes {
   /// Linked list of declaration attributes.

include/swift/AST/DiagnosticsParse.def

@@ -1763,6 +1763,28 @@ WARNING(warn_attr_unsafe_removed,none,
         "'%0' attribute has been removed in favor of @preconcurrency",
         (StringRef))
 
+// _documentation
+ERROR(documentation_attr_expected_argument,none,
+      "@_documentation attribute expected 'visibility' or 'metadata' argument",
+      ())
+ERROR(documentation_attr_unknown_argument,none,
+      "unknown argument '%0', expected 'visibility' or 'metadata'",
+      (StringRef))
+ERROR(documentation_attr_expected_access_level,none,
+      "@_documentation attribute's 'visibility' argument expected an access level",
+      ())
+ERROR(documentation_attr_unknown_access_level,none,
+      "unknown visibility '%0', expected an access level keyword",
+      (StringRef))
+ERROR(documentation_attr_duplicate_visibility,none,
+      "cannot give more than one visibility to the same item", ())
+ERROR(documentation_attr_metadata_expected_text,none,
+      "@_documentation attribute's 'metadata' argument expected an identifier or "
+      "quoted string",
+      ())
+ERROR(documentation_attr_duplicate_metadata,none,
+      "cannot give more than one metadata argument to the same item", ())
+
 //------------------------------------------------------------------------------
 // MARK: Generics parsing diagnostics
 //------------------------------------------------------------------------------

include/swift/AST/Import.h

@@ -19,6 +19,7 @@
 #ifndef SWIFT_IMPORT_H
 #define SWIFT_IMPORT_H
 
+#include "swift/AST/AttrKind.h"
 #include "swift/AST/Identifier.h"
 #include "swift/Basic/Located.h"
 #include "swift/Basic/OptionSet.h"
@@ -579,13 +580,18 @@ struct AttributedImport {
   /// is the source range covering the annotation.
   SourceRange preconcurrencyRange;
 
+  /// If the import declaration has a `@_documentation(visibility: <access>)`
+  /// attribute, this is the given access level.
+  Optional<AccessLevel> docVisibility;
+
   AttributedImport(ModuleInfo module, SourceLoc importLoc = SourceLoc(),
                    ImportOptions options = ImportOptions(),
                    StringRef filename = {}, ArrayRef<Identifier> spiGroups = {},
-                   SourceRange preconcurrencyRange = {})
+                   SourceRange preconcurrencyRange = {},
+                   Optional<AccessLevel> docVisibility = None)
       : module(module), importLoc(importLoc), options(options),
         sourceFileArg(filename), spiGroups(spiGroups),
-        preconcurrencyRange(preconcurrencyRange) {
+        preconcurrencyRange(preconcurrencyRange), docVisibility(docVisibility) {
     assert(!(options.contains(ImportFlags::Exported) &&
              options.contains(ImportFlags::ImplementationOnly)) ||
            options.contains(ImportFlags::Reserved));
@@ -595,14 +601,15 @@ struct AttributedImport {
   AttributedImport(ModuleInfo module, AttributedImport<OtherModuleInfo> other)
     : AttributedImport(module, other.importLoc, other.options,
                        other.sourceFileArg, other.spiGroups,
-                       other.preconcurrencyRange) { }
+                       other.preconcurrencyRange, other.docVisibility) { }
 
   friend bool operator==(const AttributedImport<ModuleInfo> &lhs,
                          const AttributedImport<ModuleInfo> &rhs) {
     return lhs.module == rhs.module &&
            lhs.options.toRaw() == rhs.options.toRaw() &&
            lhs.sourceFileArg == rhs.sourceFileArg &&
-           lhs.spiGroups == rhs.spiGroups;
+           lhs.spiGroups == rhs.spiGroups &&
+           lhs.docVisibility == rhs.docVisibility;
   }
 
   AttributedImport<ImportedModule> getLoaded(ModuleDecl *loadedModule) const {
@@ -754,14 +761,14 @@ struct DenseMapInfo<swift::AttributedImport<ModuleInfo>> {
                             SourceLocDMI::getEmptyKey(),
                             ImportOptionsDMI::getEmptyKey(),
                             StringRefDMI::getEmptyKey(),
-                            {});
+                            {}, {}, None);
   }
   static inline AttributedImport getTombstoneKey() {
     return AttributedImport(ModuleInfoDMI::getTombstoneKey(),
                             SourceLocDMI::getEmptyKey(),
                             ImportOptionsDMI::getTombstoneKey(),
                             StringRefDMI::getTombstoneKey(),
-                            {});
+                            {}, {}, None);
   }
   static inline unsigned getHashValue(const AttributedImport &import) {
     return detail::combineHashValue(
@@ -775,7 +782,8 @@ struct DenseMapInfo<swift::AttributedImport<ModuleInfo>> {
     return ModuleInfoDMI::isEqual(a.module, b.module) &&
            ImportOptionsDMI::isEqual(a.options, b.options) &&
            StringRefDMI::isEqual(a.sourceFileArg, b.sourceFileArg) &&
-           a.spiGroups == b.spiGroups;
+           a.spiGroups == b.spiGroups &&
+           a.docVisibility == b.docVisibility;
   }
 };
 }

include/swift/AST/Module.h

@@ -959,7 +959,8 @@ 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,
+                                  llvm::function_ref<bool(AttributedImport<ImportedModule>)> includeImport = nullptr);
 
 } // end namespace swift
 

include/swift/Parse/Parser.h

@@ -1145,6 +1145,14 @@ class Parser {
   bool parseBackDeployAttribute(DeclAttributes &Attributes, StringRef AttrName,
                                 SourceLoc AtLoc, SourceLoc Loc);
 
+  /// Parse the @_documentation attribute.
+  ParserResult<DocumentationAttr> parseDocumentationAttribute(SourceLoc AtLoc,
+                                                              SourceLoc Loc);
+
+  /// Parse a single argument from a @_documentation attribute.
+  bool parseDocumentationAttributeArgument(Optional<StringRef> &Metadata,
+                                           Optional<AccessLevel> &Visibility);
+
   /// Parse a specific attribute.
   ParserStatus parseDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc,
                                   PatternBindingInitializer *&initContext,

include/swift/SymbolGraphGen/DocumentationCategory.h

@@ -0,0 +1,48 @@
+//===--- DocumentationCategory.h - Accessors for @_documentation ----------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2022 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
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_SYMBOLGRAPHGEN_DOCUMENTATIONCATEGORY_H
+#define SWIFT_SYMBOLGRAPHGEN_DOCUMENTATIONCATEGORY_H
+
+#include "swift/AST/Decl.h"
+
+#include "llvm/Support/Compiler.h"
+
+namespace swift {
+namespace symbolgraphgen {
+
+LLVM_ATTRIBUTE_USED
+static StringRef documentationMetadataForDecl(const Decl *D) {
+  if (!D) return {};
+
+  if (const auto *DC = D->getAttrs().getAttribute<DocumentationAttr>()) {
+    return DC->Metadata;
+  }
+
+  return {};
+}
+
+LLVM_ATTRIBUTE_USED
+static Optional<AccessLevel> documentationVisibilityForDecl(const Decl *D) {
+  if (!D) return None;
+
+  if (const auto *DC = D->getAttrs().getAttribute<DocumentationAttr>()) {
+    return DC->Visibility;
+  }
+
+  return None;
+}
+
+} // namespace symbolgraphgen
+} // namespace swift
+
+#endif // SWIFT_SYMBOLGRAPHGEN_DOCUMENTATIONCATEGORY_H

lib/AST/Attr.cpp

@@ -1450,6 +1450,8 @@ StringRef DeclAttribute::getAttrName() const {
     return "_backDeploy";
   case DAK_Expose:
     return "_expose";
+  case DAK_Documentation:
+    return "_documentation";
   }
   llvm_unreachable("bad DeclAttrKind");
 }

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,
+                                         llvm::function_ref<bool(AttributedImport<ImportedModule>)> includeImport) {
   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) &&
+              (!includeImport || includeImport(import)) &&
               import.module.importedModule->shouldCollectDisplayDecls()) {
             auto *TheModule = import.module.importedModule;