Don't include serde in default features + enable serde impls in tests

conformance/Cargo.toml

@@ -8,7 +8,7 @@ authors.workspace = true
 [dependencies]
 bytes = "1"
 env_logger = { version = "0.11", default-features = false }
-prost = { path = "../prost" }
-prost-types = { path = "../prost-types", features = ["any-v2"] }
+prost = { path = "../prost", features = ["serde", "serde-json"] }
+prost-types = { path = "../prost-types", features = ["serde", "any-v2"] }
 protobuf = { path = "../protobuf" }
 tests = { path = "../tests" }

prost-build/src/code_generator.rs

@@ -384,9 +384,11 @@ impl<'a> CodeGenerator<'a> {
     }
 
     fn append_serde(&mut self) {
-        push_indent(self.buf, self.depth);
-        self.buf.push_str("#[prost(serde)]");
-        self.buf.push('\n');
+        if self.config.enable_serde {
+            push_indent(self.buf, self.depth);
+            self.buf.push_str("#[prost(serde)]");
+            self.buf.push('\n');
+        }
     }
 
     fn append_enum_attributes(&mut self, fq_message_name: &str) {
@@ -512,12 +514,14 @@ impl<'a> CodeGenerator<'a> {
         let rust_field_name = &field.rust_name();
         let proto_field_name = field.descriptor.name();
 
-        if !ident::is_stable_ident_for_json(
+        let field_name_is_stable_for_json = ident::is_stable_ident_for_json(
             proto_field_name,
             IdentKind::MessageField {
                 field: rust_field_name,
             },
-        ) {
+        );
+
+        if self.config.enable_serde && !field_name_is_stable_for_json {
             self.buf
                 .push_str(&format!(", json(proto_name = \"{}\")", proto_field_name));
         }
@@ -583,12 +587,14 @@ impl<'a> CodeGenerator<'a> {
         let rust_field_name = &field.rust_name();
         let proto_field_name = field.descriptor.name();
 
-        let json_attr = if !ident::is_stable_ident_for_json(
+        let field_name_is_stable_for_json = ident::is_stable_ident_for_json(
             proto_field_name,
             IdentKind::MessageField {
                 field: rust_field_name,
             },
-        ) {
+        );
+
+        let json_attr = if self.config.enable_serde && !field_name_is_stable_for_json {
             format!(", json(proto_name = \"{}\")", proto_field_name)
         } else {
             Default::default()
@@ -685,12 +691,14 @@ impl<'a> CodeGenerator<'a> {
             let ty_tag = self.field_type_tag(&field.descriptor);
             let ty = self.resolve_type(&field.descriptor, fq_message_name);
 
-            let json_attr = if !ident::is_stable_ident_for_json(
+            let variant_name_is_stable_for_json = ident::is_stable_ident_for_json(
                 proto_field_name,
                 IdentKind::OneOfVariant {
                     variant: rust_variant_name,
                 },
-            ) {
+            );
+
+            let json_attr = if self.config.enable_serde && !variant_name_is_stable_for_json {
                 format!(", json(proto_name = \"{}\")", proto_field_name)
             } else {
                 Default::default()
@@ -809,15 +817,18 @@ impl<'a> CodeGenerator<'a> {
 
             self.append_doc(&fq_proto_enum_name, Some(variant.proto_name));
 
-            let emit_proto_names = !variant.proto_aliases.is_empty()
-                || !ident::is_stable_ident_for_json(
-                    variant.proto_name,
-                    IdentKind::EnumVariant {
-                        ty: &enum_name,
-                        variant: &variant.generated_variant_name,
-                    },
-                );
-            if emit_proto_names {
+            let variant_name_is_stable_for_json = ident::is_stable_ident_for_json(
+                variant.proto_name,
+                IdentKind::EnumVariant {
+                    ty: &enum_name,
+                    variant: &variant.generated_variant_name,
+                },
+            );
+
+            let emit_proto_names =
+                !variant.proto_aliases.is_empty() || !variant_name_is_stable_for_json;
+
+            if self.config.enable_serde && emit_proto_names {
                 self.push_indent();
 
                 let names = iter::once(variant.proto_name)

prost-build/src/config.rs

@@ -52,6 +52,7 @@ pub struct Config {
     pub(crate) prost_path: Option<String>,
     #[cfg(feature = "format")]
     pub(crate) fmt: bool,
+    pub(crate) enable_serde: bool,
 }
 
 impl Config {
@@ -1126,6 +1127,14 @@ impl Config {
             *buf = with_generated;
         }
     }
+
+    /// Configures the code generator to also emit serde compatible serialization impls.
+    ///
+    /// Defaults to `false`.
+    pub fn enable_serde(&mut self) -> &mut Self {
+        self.enable_serde = true;
+        self
+    }
 }
 
 /// Write a slice as the entire contents of a file.
@@ -1176,6 +1185,7 @@ impl default::Default for Config {
             prost_path: None,
             #[cfg(feature = "format")]
             fmt: true,
+            enable_serde: false,
         }
     }
 }

prost-build/src/lib.rs

@@ -359,6 +359,7 @@ mod tests {
         let tempdir = tempfile::tempdir().unwrap();
 
         Config::new()
+            .enable_serde()
             .service_generator(Box::new(ServiceTraitGenerator))
             .out_dir(tempdir.path())
             .compile_protos(&["src/fixtures/smoke_test/smoke_test.proto"], &["src"])
@@ -374,6 +375,7 @@ mod tests {
         let gen = MockServiceGenerator::new(Rc::clone(&state));
 
         Config::new()
+            .enable_serde()
             .service_generator(Box::new(gen))
             .include_file("_protos.rs")
             .out_dir(tempdir.path())
@@ -398,6 +400,8 @@ mod tests {
         let tempdir = tempfile::tempdir().unwrap();
 
         let mut config = Config::new();
+        config.enable_serde();
+
         config
             .out_dir(tempdir.path())
             // Add attributes to all messages and enums
@@ -453,6 +457,7 @@ mod tests {
         let previously_empty_proto_path = tempdir.path().join(Path::new("google.protobuf.rs"));
 
         Config::new()
+            .enable_serde()
             .service_generator(Box::new(gen))
             .include_file(include_file)
             .out_dir(tempdir.path())
@@ -486,6 +491,7 @@ mod tests {
         let tempdir = tempfile::tempdir().unwrap();
 
         Config::new()
+            .enable_serde()
             .out_dir(tempdir.path())
             .boxed("Container.data.foo")
             .boxed("Bar.qux")
@@ -527,6 +533,7 @@ mod tests {
             let tempdir = tempfile::tempdir().unwrap();
 
             Config::new()
+                .enable_serde()
                 .service_generator(Box::new(gen))
                 .include_file(include_file)
                 .out_dir(tempdir.path())
@@ -579,6 +586,7 @@ mod tests {
 
         let mut buf = Vec::new();
         Config::new()
+            .enable_serde()
             .default_package_filename("_.default")
             .write_includes(modules.iter().collect(), &mut buf, None, &file_names)
             .unwrap();

prost-types/Cargo.toml

@@ -13,7 +13,7 @@ rust-version.workspace = true
 doctest = false
 
 [features]
-default = ["std", "serde", "any-v2"]
+default = ["std"]
 std = ["prost/std"]
 serde = ["prost/serde"]
 any-v2 = ["std", "serde", "prost/serde-json", "dep:serde", "dep:erased-serde"]

prost/Cargo.toml

@@ -16,7 +16,7 @@ rust-version.workspace = true
 bench = false
 
 [features]
-default = ["derive", "std", "serde", "serde-json"]
+default = ["derive", "std"]
 derive = ["dep:prost-derive"]
 prost-derive = ["derive"]                          # deprecated, please use derive feature instead
 no-recursion-limit = []

protobuf/build.rs

@@ -37,11 +37,13 @@ fn main() -> Result<()> {
     }
 
     let conformance_proto_dir = src_dir.join("conformance");
-    prost_build::compile_protos(
-        &[conformance_proto_dir.join("conformance.proto")],
-        &[conformance_proto_dir],
-    )
-    .unwrap();
+    prost_build::Config::new()
+        .enable_serde()
+        .compile_protos(
+            &[conformance_proto_dir.join("conformance.proto")],
+            &[conformance_proto_dir],
+        )
+        .unwrap();
 
     let proto_dir = src_dir.join("src");
 
@@ -51,6 +53,7 @@ fn main() -> Result<()> {
     // values.
     prost_build::Config::new()
         .btree_map(["."])
+        .enable_serde()
         .compile_protos(
             &[
                 proto_dir.join("google/protobuf/test_messages_proto2.proto"),

tests/single-include/Cargo.toml

@@ -7,7 +7,7 @@ publish = false
 license = "MIT"
 
 [dependencies]
-prost = { path = "../../prost" }
+prost = { path = "../../prost", features = ["serde"] }
 
 [build-dependencies]
 prost-build = { path = "../../prost-build" }

tests/single-include/build.rs

@@ -2,11 +2,13 @@ use prost_build::Config;
 
 fn main() {
     Config::new()
+        .enable_serde()
         .include_file("lib.rs")
         .compile_protos(&["protos/search.proto"], &["protos"])
         .unwrap();
 
     Config::new()
+        .enable_serde()
         .out_dir("src/outdir")
         .include_file("mod.rs")
         .compile_protos(&["protos/outdir.proto"], &["protos"])

tests/src/build.rs

@@ -25,6 +25,7 @@ fn main() {
     // compare based on the Rust PartialEq implementations is difficult, due to presence of NaN
     // values.
     let mut config = prost_build::Config::new();
+    config.enable_serde();
     config.btree_map(["."]);
     // Tests for custom attributes
     config.type_attribute("Foo.Bar_Baz.Foo_barBaz", "#[derive(Eq, PartialOrd, Ord)]");
@@ -128,12 +129,14 @@ fn main() {
         .unwrap();
 
     prost_build::Config::new()
+        .enable_serde()
         .protoc_arg("--experimental_allow_proto3_optional")
         .compile_protos(&[src.join("proto3_presence.proto")], includes)
         .unwrap();
 
     {
         let mut config = prost_build::Config::new();
+        config.enable_serde();
         config.disable_comments(["."]);
 
         config
@@ -152,6 +155,7 @@ fn main() {
     std::fs::create_dir_all(&out_path).unwrap();
 
     prost_build::Config::new()
+        .enable_serde()
         .bytes(["."])
         .out_dir(out_path)
         .include_file("wellknown_include.rs")
@@ -166,6 +170,7 @@ fn main() {
         .unwrap();
 
     prost_build::Config::new()
+        .enable_serde()
         .enable_type_names()
         .type_name_domain([".type_names.Foo"], "tests")
         .compile_protos(&[src.join("type_names.proto")], includes)
@@ -184,6 +189,7 @@ fn main() {
     fs::create_dir_all(&no_root_packages).expect("failed to create prefix directory");
     let mut no_root_packages_config = prost_build::Config::new();
     no_root_packages_config
+        .enable_serde()
         .out_dir(&no_root_packages)
         .default_package_filename("__.default")
         .include_file("__.include.rs")
@@ -199,6 +205,7 @@ fn main() {
     fs::create_dir_all(&no_root_packages_with_default).expect("failed to create prefix directory");
     let mut no_root_packages_config = prost_build::Config::new();
     no_root_packages_config
+        .enable_serde()
         .out_dir(&no_root_packages_with_default)
         .compile_protos(
             &[src.join("no_root_packages/widget_factory.proto")],