[ObjC] add "generate_minimal_imports" generation option

This new option will cause only the files that provide types to
be imported into the generated code. This helps reduce the inputs
that aren't needed (folks ignoring the protoc warnings) and for
things imported only for custom options as the objc generated code
doesn't capture those and thus the imports aren't needed in the
generated code.

Also do some general import cleanups.

PiperOrigin-RevId: 558867748

Author: thomasvl

src/google/protobuf/compiler/objectivec/enum_field.cc

@@ -32,8 +32,14 @@
 
 #include <string>
 
+#include "absl/container/btree_set.h"
 #include "absl/container/flat_hash_map.h"
+#include "absl/container/flat_hash_set.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+#include "google/protobuf/compiler/objectivec/field.h"
 #include "google/protobuf/compiler/objectivec/names.h"
+#include "google/protobuf/descriptor.h"
 #include "google/protobuf/io/printer.h"
 
 namespace google {
@@ -135,6 +141,13 @@ void EnumFieldGenerator::DetermineForwardDeclarations(
   }
 }
 
+void EnumFieldGenerator::DetermineNeededFiles(
+    absl::flat_hash_set<const FileDescriptor*>* deps) const {
+  if (descriptor_->file() != descriptor_->enum_type()->file()) {
+    deps->insert(descriptor_->enum_type()->file());
+  }
+}
+
 RepeatedEnumFieldGenerator::RepeatedEnumFieldGenerator(
     const FieldDescriptor* descriptor)
     : RepeatedFieldGenerator(descriptor) {
@@ -153,6 +166,13 @@ void RepeatedEnumFieldGenerator::EmitArrayComment(io::Printer* printer) const {
 // because `GPBEnumArray` isn't generic (like `NSArray` would be for messages)
 // and thus doesn't reference the type in the header.
 
+void RepeatedEnumFieldGenerator::DetermineNeededFiles(
+    absl::flat_hash_set<const FileDescriptor*>* deps) const {
+  if (descriptor_->file() != descriptor_->enum_type()->file()) {
+    deps->insert(descriptor_->enum_type()->file());
+  }
+}
+
 }  // namespace objectivec
 }  // namespace compiler
 }  // namespace protobuf

src/google/protobuf/compiler/objectivec/enum_field.h

@@ -34,7 +34,9 @@
 #include <string>
 
 #include "absl/container/btree_set.h"
+#include "absl/container/flat_hash_set.h"
 #include "google/protobuf/compiler/objectivec/field.h"
+#include "google/protobuf/descriptor.h"
 
 namespace google {
 namespace protobuf {
@@ -52,6 +54,8 @@ class EnumFieldGenerator : public SingleFieldGenerator {
   void GenerateCFunctionImplementations(io::Printer* printer) const override;
   void DetermineForwardDeclarations(absl::btree_set<std::string>* fwd_decls,
                                     bool include_external_types) const override;
+  void DetermineNeededFiles(
+      absl::flat_hash_set<const FileDescriptor*>* deps) const override;
 
  protected:
   explicit EnumFieldGenerator(const FieldDescriptor* descriptor);
@@ -63,6 +67,8 @@ class RepeatedEnumFieldGenerator : public RepeatedFieldGenerator {
 
  public:
   void EmitArrayComment(io::Printer* printer) const override;
+  void DetermineNeededFiles(
+      absl::flat_hash_set<const FileDescriptor*>* deps) const override;
 
  protected:
   explicit RepeatedEnumFieldGenerator(const FieldDescriptor* descriptor);

src/google/protobuf/compiler/objectivec/extension.cc

@@ -34,9 +34,13 @@
 #include <vector>
 
 #include "absl/container/btree_set.h"
+#include "absl/container/flat_hash_set.h"
+#include "absl/log/absl_check.h"
 #include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
 #include "google/protobuf/compiler/objectivec/helpers.h"
 #include "google/protobuf/compiler/objectivec/names.h"
+#include "google/protobuf/descriptor.h"
 #include "google/protobuf/descriptor.pb.h"
 #include "google/protobuf/io/printer.h"
 
@@ -128,6 +132,27 @@ void ExtensionGenerator::DetermineObjectiveCClassDefinitions(
   }
 }
 
+void ExtensionGenerator::DetermineNeededFiles(
+    absl::flat_hash_set<const FileDescriptor*>* deps) const {
+  const Descriptor* extended_type = descriptor_->containing_type();
+  if (descriptor_->file() != extended_type->file()) {
+    deps->insert(extended_type->file());
+  }
+
+  const ObjectiveCType objc_type = GetObjectiveCType(descriptor_);
+  if (objc_type == OBJECTIVECTYPE_MESSAGE) {
+    const Descriptor* value_msg_descriptor = descriptor_->message_type();
+    if (descriptor_->file() != value_msg_descriptor->file()) {
+      deps->insert(value_msg_descriptor->file());
+    }
+  } else if (objc_type == OBJECTIVECTYPE_ENUM) {
+    const EnumDescriptor* value_enum_descriptor = descriptor_->enum_type();
+    if (descriptor_->file() != value_enum_descriptor->file()) {
+      deps->insert(value_enum_descriptor->file());
+    }
+  }
+}
+
 void ExtensionGenerator::GenerateRegistrationSource(
     io::Printer* printer) const {
   printer->Emit({{"full_method_name", full_method_name_}},

src/google/protobuf/compiler/objectivec/extension.h

@@ -34,6 +34,8 @@
 #include <string>
 
 #include "absl/container/btree_set.h"
+#include "absl/container/flat_hash_set.h"
+#include "absl/strings/string_view.h"
 #include "google/protobuf/descriptor.h"
 #include "google/protobuf/io/printer.h"
 
@@ -56,6 +58,8 @@ class ExtensionGenerator {
   void GenerateRegistrationSource(io::Printer* printer) const;
   void DetermineObjectiveCClassDefinitions(
       absl::btree_set<std::string>* fwd_decls) const;
+  void DetermineNeededFiles(
+      absl::flat_hash_set<const FileDescriptor*>* deps) const;
 
  private:
   std::string method_name_;

src/google/protobuf/compiler/objectivec/field.cc

@@ -34,16 +34,20 @@
 #include <string>
 #include <vector>
 
+#include "absl/container/btree_set.h"
 #include "absl/container/flat_hash_map.h"
+#include "absl/container/flat_hash_set.h"
 #include "absl/log/absl_check.h"
 #include "absl/log/absl_log.h"
 #include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
 #include "google/protobuf/compiler/objectivec/enum_field.h"
 #include "google/protobuf/compiler/objectivec/helpers.h"
 #include "google/protobuf/compiler/objectivec/map_field.h"
 #include "google/protobuf/compiler/objectivec/message_field.h"
 #include "google/protobuf/compiler/objectivec/names.h"
 #include "google/protobuf/compiler/objectivec/primitive_field.h"
+#include "google/protobuf/descriptor.h"
 #include "google/protobuf/io/printer.h"
 
 namespace google {
@@ -237,6 +241,11 @@ void FieldGenerator::DetermineObjectiveCClassDefinitions(
   // Nothing
 }
 
+void FieldGenerator::DetermineNeededFiles(
+    absl::flat_hash_set<const FileDescriptor*>* deps) const {
+  // Nothing
+}
+
 void FieldGenerator::GenerateFieldDescription(io::Printer* printer,
                                               bool include_default) const {
   // Printed in the same order as the structure decl.

src/google/protobuf/compiler/objectivec/field.h

@@ -37,7 +37,9 @@
 
 #include "absl/container/btree_set.h"
 #include "absl/container/flat_hash_map.h"
+#include "absl/container/flat_hash_set.h"
 #include "absl/strings/match.h"
+#include "absl/strings/string_view.h"
 #include "google/protobuf/descriptor.h"
 #include "google/protobuf/io/printer.h"
 
@@ -73,6 +75,8 @@ class FieldGenerator {
       bool include_external_types) const;
   virtual void DetermineObjectiveCClassDefinitions(
       absl::btree_set<std::string>* fwd_decls) const;
+  virtual void DetermineNeededFiles(
+      absl::flat_hash_set<const FileDescriptor*>* deps) const;
 
   // Used during generation, not intended to be extended by subclasses.
   void GenerateFieldDescription(io::Printer* printer,

src/google/protobuf/compiler/objectivec/file.cc

@@ -486,6 +486,7 @@ void FileGenerator::GenerateFile(io::Printer* p, GeneratedFileType file_type,
       /* for_bundled_proto = */ is_bundled_proto_);
   const std::string header_extension(kHeaderExtension);
 
+  absl::flat_hash_set<const FileDescriptor*> file_imports;
   switch (file_type) {
     case GeneratedFileType::kHeader:
       // Generated files bundled with the library get minimal imports,
@@ -500,35 +501,50 @@ void FileGenerator::GenerateFile(io::Printer* p, GeneratedFileType file_type,
       if (HeadersUseForwardDeclarations()) {
         // #import any headers for "public imports" in the proto file.
         for (int i = 0; i < file_->public_dependency_count(); i++) {
-          import_writer.AddFile(file_->public_dependency(i), header_extension);
+          file_imports.insert(file_->public_dependency(i));
         }
+      } else if (generation_options_.generate_minimal_imports) {
+        DetermineNeededDeps(&file_imports, PublicDepsHandling::kForceInclude);
       } else {
         for (int i = 0; i < file_->dependency_count(); i++) {
-          import_writer.AddFile(file_->dependency(i), header_extension);
+          file_imports.insert(file_->dependency(i));
         }
       }
       break;
     case GeneratedFileType::kSource:
       import_writer.AddRuntimeImport("GPBProtocolBuffers_RuntimeSupport.h");
       import_writer.AddFile(file_, header_extension);
       if (HeadersUseForwardDeclarations()) {
-        // #import the headers for anything that a plain dependency of this
-        // proto file (that means they were just an include, not a "public"
-        // include).
-        absl::flat_hash_set<std::string> public_import_names;
-        for (int i = 0; i < file_->public_dependency_count(); i++) {
-          public_import_names.insert(file_->public_dependency(i)->name());
-        }
-        for (int i = 0; i < file_->dependency_count(); i++) {
-          const FileDescriptor* dep = file_->dependency(i);
-          if (!public_import_names.contains(dep->name())) {
-            import_writer.AddFile(dep, header_extension);
+        if (generation_options_.generate_minimal_imports) {
+          DetermineNeededDeps(&file_imports, PublicDepsHandling::kExclude);
+        } else {
+          // #import the headers for anything that a plain dependency of this
+          // proto file (that means they were just an include, not a "public"
+          // include).
+          absl::flat_hash_set<std::string> public_import_names;
+          for (int i = 0; i < file_->public_dependency_count(); i++) {
+            public_import_names.insert(file_->public_dependency(i)->name());
+          }
+          for (int i = 0; i < file_->dependency_count(); i++) {
+            const FileDescriptor* dep = file_->dependency(i);
+            if (!public_import_names.contains(dep->name())) {
+              file_imports.insert(dep);
+            }
           }
         }
       }
       break;
   }
 
+  if (!file_imports.empty()) {
+    for (int i = 0; i < file_->dependency_count(); i++) {
+      const FileDescriptor* dep = file_->dependency(i);
+      if (file_imports.contains(dep)) {
+        import_writer.AddFile(file_->dependency(i), header_extension);
+      }
+    }
+  }
+
   for (const auto& dep : file_options.extra_files_to_import) {
     import_writer.AddFile(dep, header_extension);
   }
@@ -752,6 +768,34 @@ void FileGenerator::EmitFileDescription(io::Printer* p) const {
   p->Emit("\n");
 }
 
+void FileGenerator::DetermineNeededDeps(
+    absl::flat_hash_set<const FileDescriptor*>* deps,
+    PublicDepsHandling public_deps_handling) const {
+  // This logic captures the deps that are needed for types thus removing the
+  // ones that are only deps because they provide the definitions for custom
+  // options. If protoc gets something like "import options" then this logic can
+  // go away as the non "import options" deps would be the ones needed.
+
+  if (public_deps_handling == PublicDepsHandling::kForceInclude) {
+    for (int i = 0; i < file_->public_dependency_count(); i++) {
+      deps->insert(file_->public_dependency(i));
+    }
+  }
+
+  for (const auto& generator : message_generators_) {
+    generator->DetermineNeededFiles(deps);
+  }
+  for (const auto& generator : extension_generators_) {
+    generator->DetermineNeededFiles(deps);
+  }
+
+  if (public_deps_handling == PublicDepsHandling::kExclude) {
+    for (int i = 0; i < file_->public_dependency_count(); i++) {
+      deps->erase(file_);
+    }
+  }
+}
+
 }  // namespace objectivec
 }  // namespace compiler
 }  // namespace protobuf

src/google/protobuf/compiler/objectivec/file.h

@@ -121,6 +121,10 @@ class FileGenerator {
       const std::vector<const FileDescriptor*>& deps_with_extensions) const;
   void EmitFileDescription(io::Printer* p) const;
 
+  enum class PublicDepsHandling : int { kAsUsed, kForceInclude, kExclude };
+  void DetermineNeededDeps(absl::flat_hash_set<const FileDescriptor*>* deps,
+                           PublicDepsHandling public_deps_handling) const;
+
   bool HeadersUseForwardDeclarations() const {
     // The bundled protos (WKTs) don't make use of forward declarations.
     return !is_bundled_proto_ &&

src/google/protobuf/compiler/objectivec/generator.cc

@@ -274,6 +274,18 @@ bool ObjectiveCGenerator::GenerateAll(
                               options[i].second);
         return false;
       }
+    } else if (options[i].first == "generate_minimal_imports") {
+      // Controls if minimal imports should be generated from a files imports.
+      // Since custom options require imports, they current cause generated
+      // imports even though there is nothing captured in the generated code,
+      // this provides smaller imports only for the things referenced.
+      if (!StringToBool(options[i].second,
+                        &generation_options.generate_minimal_imports)) {
+        *error =
+            absl::StrCat("error: Unknown value for generate_minimal_imports: ",
+                         options[i].second);
+        return false;
+      }
     } else if (options[i].first == "experimental_multi_source_generation") {
       // This is an experimental option, and could be removed or change at any
       // time; it is not documented in the README.md for that reason.

src/google/protobuf/compiler/objectivec/helpers.h

@@ -36,6 +36,7 @@
 #include <string>
 #include <vector>
 
+#include "absl/strings/str_cat.h"
 #include "absl/strings/string_view.h"
 #include "google/protobuf/descriptor.h"
 #include "google/protobuf/descriptor.pb.h"