chore: improve no_std maintainability:

README.md

@@ -332,21 +332,21 @@ and the generated Rust code (`tutorial.rs`):
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct Person {
     #[prost(string, tag="1")]
-    pub name: ::prost::alloc::string::String,
+    pub name: String,
     /// Unique ID number for this person.
     #[prost(int32, tag="2")]
     pub id: i32,
     #[prost(string, tag="3")]
-    pub email: ::prost::alloc::string::String,
+    pub email: String,
     #[prost(message, repeated, tag="4")]
-    pub phones: ::prost::alloc::vec::Vec<person::PhoneNumber>,
+    pub phones: Vec<person::PhoneNumber>,
 }
 /// Nested message and enum types in `Person`.
 pub mod person {
     #[derive(Clone, PartialEq, ::prost::Message)]
     pub struct PhoneNumber {
         #[prost(string, tag="1")]
-        pub number: ::prost::alloc::string::String,
+        pub number: String,
         #[prost(enumeration="PhoneType", tag="2")]
         pub r#type: i32,
     }
@@ -362,7 +362,7 @@ pub mod person {
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct AddressBook {
     #[prost(message, repeated, tag="1")]
-    pub people: ::prost::alloc::vec::Vec<Person>,
+    pub people: Vec<Person>,
 }
 ```
 

conformance/src/main.rs

@@ -1,6 +1,5 @@
-use std::io::{self, Read, Write};
-
 use bytes::{Buf, BufMut};
+use prost::facade::*;
 use prost::Message;
 
 use protobuf::conformance::{

prost-build/src/code_generator.rs

@@ -1,11 +1,7 @@
-use std::ascii;
-use std::borrow::Cow;
-use std::collections::{HashMap, HashSet};
-use std::iter;
-
 use itertools::{Either, Itertools};
 use log::debug;
 use multimap::MultiMap;
+use prost::facade::*;
 use prost_types::field_descriptor_proto::{Label, Type};
 use prost_types::source_code_info::Location;
 use prost_types::{
@@ -88,6 +84,8 @@ impl<'a> CodeGenerator<'a> {
             buf,
         };
 
+        code_gen.add_prelude();
+
         debug!(
             "file: {:?}, package: {:?}",
             file.name.as_ref().unwrap(),
@@ -286,10 +284,6 @@ impl<'a> CodeGenerator<'a> {
             "const PACKAGE: &'static str = \"{}\";\n",
             self.package,
         ));
-
-        let prost_path = self.config.prost_path.as_deref().unwrap_or("::prost");
-        let string_path = format!("{prost_path}::alloc::string::String");
-
         let full_name = format!(
             "{}{}{}{}{message_name}",
             self.package.trim_matches('.'),
@@ -304,11 +298,11 @@ impl<'a> CodeGenerator<'a> {
             .map_or("", |name| name.as_str());
 
         self.buf.push_str(&format!(
-            r#"fn full_name() -> {string_path} {{ "{full_name}".into() }}"#,
+            r#"fn full_name() -> String {{ "{full_name}".into() }}"#,
         ));
 
         self.buf.push_str(&format!(
-            r#"fn type_url() -> {string_path} {{ "{domain_name}/{full_name}".into() }}"#,
+            r#"fn type_url() -> String {{ "{domain_name}/{full_name}".into() }}"#,
         ));
 
         self.depth -= 1;
@@ -479,17 +473,13 @@ impl<'a> CodeGenerator<'a> {
         self.buf.push_str(&to_snake(field.name()));
         self.buf.push_str(": ");
 
-        let prost_path = prost_path(self.config);
-
         if repeated {
-            self.buf
-                .push_str(&format!("{}::alloc::vec::Vec<", prost_path));
+            self.buf.push_str("Vec<");
         } else if optional {
             self.buf.push_str("::core::option::Option<");
         }
         if boxed {
-            self.buf
-                .push_str(&format!("{}::alloc::boxed::Box<", prost_path));
+            self.buf.push_str("Box<");
         }
         self.buf.push_str(&ty);
         if boxed {
@@ -644,11 +634,8 @@ impl<'a> CodeGenerator<'a> {
             );
 
             if boxed {
-                self.buf.push_str(&format!(
-                    "{}(::prost::alloc::boxed::Box<{}>),\n",
-                    to_upper_camel(field.name()),
-                    ty
-                ));
+                self.buf
+                    .push_str(&format!("{}(Box<{}>),\n", to_upper_camel(field.name()), ty));
             } else {
                 self.buf
                     .push_str(&format!("{}({}),\n", to_upper_camel(field.name()), ty));
@@ -911,6 +898,7 @@ impl<'a> CodeGenerator<'a> {
         self.buf.push_str("pub mod ");
         self.buf.push_str(&to_snake(module));
         self.buf.push_str(" {\n");
+        self.add_prelude();
 
         self.type_path.push(module.into());
 
@@ -935,7 +923,7 @@ impl<'a> CodeGenerator<'a> {
             Type::Int32 | Type::Sfixed32 | Type::Sint32 | Type::Enum => String::from("i32"),
             Type::Int64 | Type::Sfixed64 | Type::Sint64 => String::from("i64"),
             Type::Bool => String::from("bool"),
-            Type::String => format!("{}::alloc::string::String", prost_path(self.config)),
+            Type::String => "String".to_string(),
             Type::Bytes => self
                 .config
                 .bytes_type
@@ -1056,6 +1044,12 @@ impl<'a> CodeGenerator<'a> {
             message_name,
         )
     }
+
+    fn add_prelude(&mut self) {
+        self.buf.push_str("#[allow(unused_imports)]");
+        self.buf
+            .push_str(&format!("use {}::facade::*;", prost_path(self.config)));
+    }
 }
 
 /// Returns `true` if the repeated field type can be packed.

prost-build/src/collections.rs

@@ -2,10 +2,11 @@
 #[non_exhaustive]
 #[derive(Default, Clone, Copy, Debug, PartialEq)]
 pub(crate) enum MapType {
+    // IMPROVEMENT: place behind std feature flag
     /// The [`std::collections::HashMap`] type.
     #[default]
     HashMap,
-    /// The [`std::collections::BTreeMap`] type.
+    /// The [`alloc::collections::BTreeMap`] type.
     BTreeMap,
 }
 
@@ -32,8 +33,8 @@ impl MapType {
     /// The fully-qualified Rust type corresponding to the map type.
     pub fn rust_type(&self) -> &'static str {
         match self {
-            MapType::HashMap => "::std::collections::HashMap",
-            MapType::BTreeMap => "::prost::alloc::collections::BTreeMap",
+            MapType::HashMap => "HashMap",
+            MapType::BTreeMap => "BTreeMap",
         }
     }
 }
@@ -50,7 +51,7 @@ impl BytesType {
     /// The fully-qualified Rust type corresponding to the bytes type.
     pub fn rust_type(&self) -> &'static str {
         match self {
-            BytesType::Vec => "::prost::alloc::vec::Vec<u8>",
+            BytesType::Vec => "Vec<u8>",
             BytesType::Bytes => "::prost::bytes::Bytes",
         }
     }

prost-build/src/config.rs

@@ -1,6 +1,3 @@
-use std::collections::HashMap;
-use std::default;
-use std::env;
 use std::ffi::{OsStr, OsString};
 use std::fmt;
 use std::fs;
@@ -11,6 +8,7 @@ use std::process::Command;
 use log::debug;
 use log::trace;
 
+use prost::facade::*;
 use prost::Message;
 use prost_types::{FileDescriptorProto, FileDescriptorSet};
 

prost-build/src/extern_paths.rs

@@ -1,9 +1,9 @@
-use std::collections::{hash_map, HashMap};
-
 use itertools::Itertools;
 
 use crate::ident::{to_snake, to_upper_camel};
 
+use prost::facade::*;
+
 fn validate_proto_path(path: &str) -> Result<(), String> {
     if path.chars().next().map(|c| c != '.').unwrap_or(true) {
         return Err(format!(
@@ -37,7 +37,7 @@ impl ExternPaths {
             extern_paths.insert(".google.protobuf.BoolValue".to_string(), "bool".to_string())?;
             extern_paths.insert(
                 ".google.protobuf.BytesValue".to_string(),
-                "::prost::alloc::vec::Vec<u8>".to_string(),
+                "Vec<u8>".to_string(),
             )?;
             extern_paths.insert(
                 ".google.protobuf.DoubleValue".to_string(),
@@ -49,7 +49,7 @@ impl ExternPaths {
             extern_paths.insert(".google.protobuf.Int64Value".to_string(), "i64".to_string())?;
             extern_paths.insert(
                 ".google.protobuf.StringValue".to_string(),
-                "::prost::alloc::string::String".to_string(),
+                "String".to_string(),
             )?;
             extern_paths.insert(
                 ".google.protobuf.UInt32Value".to_string(),

prost-build/src/fixtures/field_attributes/_expected_field_attributes.rs

@@ -2,33 +2,32 @@
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct Container {
-    #[prost(oneof="container::Data", tags="1, 2")]
+    #[prost(oneof = "container::Data", tags = "1, 2")]
     pub data: ::core::option::Option<container::Data>,
 }
 /// Nested message and enum types in `Container`.
 pub mod container {
     #[allow(clippy::derive_partial_eq_without_eq)]
-#[derive(Clone, PartialEq, ::prost::Oneof)]
+    #[derive(Clone, PartialEq, ::prost::Oneof)]
     pub enum Data {
-        #[prost(message, tag="1")]
-        Foo(::prost::alloc::boxed::Box<super::Foo>),
-        #[prost(message, tag="2")]
+        #[prost(message, tag = "1")]
+        Foo(Box<super::Foo>),
+        #[prost(message, tag = "2")]
         Bar(super::Bar),
     }
 }
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct Foo {
-    #[prost(string, tag="1")]
-    pub foo: ::prost::alloc::string::String,
+    #[prost(string, tag = "1")]
+    pub foo: String,
 }
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct Bar {
-    #[prost(message, optional, boxed, tag="1")]
-    pub qux: ::core::option::Option<::prost::alloc::boxed::Box<Qux>>,
+    #[prost(message, optional, boxed, tag = "1")]
+    pub qux: ::core::option::Option<Box<Qux>>,
 }
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
-pub struct Qux {
-}
+pub struct Qux {}

prost-build/src/fixtures/field_attributes/_expected_field_attributes_formatted.rs

@@ -3,15 +3,15 @@
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct Container {
     #[prost(oneof = "container::Data", tags = "1, 2")]
-    pub data: ::core::option::Option<container::Data>,
+    pub data: Option<container::Data>,
 }
 /// Nested message and enum types in `Container`.
 pub mod container {
     #[allow(clippy::derive_partial_eq_without_eq)]
     #[derive(Clone, PartialEq, ::prost::Oneof)]
     pub enum Data {
         #[prost(message, tag = "1")]
-        Foo(::prost::alloc::boxed::Box<super::Foo>),
+        Foo(Box<super::Foo>),
         #[prost(message, tag = "2")]
         Bar(super::Bar),
     }
@@ -20,13 +20,13 @@ pub mod container {
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct Foo {
     #[prost(string, tag = "1")]
-    pub foo: ::prost::alloc::string::String,
+    pub foo: String,
 }
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct Bar {
     #[prost(message, optional, boxed, tag = "1")]
-    pub qux: ::core::option::Option<::prost::alloc::boxed::Box<Qux>>,
+    pub qux: Option<Box<Qux>>,
 }
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]

prost-build/src/fixtures/helloworld/_expected_helloworld.rs

@@ -3,15 +3,15 @@
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct Message {
-    #[prost(string, tag="1")]
-    pub say: ::prost::alloc::string::String,
+    #[prost(string, tag = "1")]
+    pub say: String,
 }
 #[derive(derive_builder::Builder)]
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct Response {
-    #[prost(string, tag="1")]
-    pub say: ::prost::alloc::string::String,
+    #[prost(string, tag = "1")]
+    pub say: String,
 }
 #[some_enum_attr(u8)]
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord, ::prost::Enumeration)]

prost-build/src/fixtures/helloworld/_expected_helloworld_formatted.rs

@@ -4,14 +4,14 @@
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct Message {
     #[prost(string, tag = "1")]
-    pub say: ::prost::alloc::string::String,
+    pub say: String,
 }
 #[derive(derive_builder::Builder)]
 #[allow(clippy::derive_partial_eq_without_eq)]
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct Response {
     #[prost(string, tag = "1")]
-    pub say: ::prost::alloc::string::String,
+    pub say: String,
 }
 #[some_enum_attr(u8)]
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord, ::prost::Enumeration)]