Make prost a no_std compatible library, and prost-build able to gen…

Cargo.toml

@@ -36,12 +36,13 @@ exclude = [
 bench = false
 
 [features]
-default = ["prost-derive"]
+default = ["prost-derive", "std"]
 no-recursion-limit = []
+std = [] # When std is disabled, we provide no_std support in prost
 
 [dependencies]
-bytes = "0.5"
-prost-derive = { version = "0.6.1", path = "prost-derive", optional = true }
+bytes = { version = "0.5", default-features = false }
+prost-derive = { version = "0.6.1", path = "prost-derive", default-features = false, optional = true }
 
 [dev-dependencies]
 criterion = "0.3"

conformance/Cargo.toml

@@ -6,7 +6,7 @@ publish = false
 edition = "2018"
 
 [dependencies]
-bytes = "0.5"
+bytes = { version = "0.5", default-features = false }
 env_logger = { version = "0.7", default-features = false }
 log = "0.4"
 prost = { path = ".." }

prost-build/Cargo.toml

@@ -10,14 +10,14 @@ description = "A Protocol Buffers implementation for the Rust Language."
 edition = "2018"
 
 [dependencies]
-bytes = "0.5"
+bytes = { version = "0.5", default-features = false }
 heck = "0.3"
 itertools = "0.8"
 log = "0.4"
 multimap = { version = "0.8", default-features = false }
 petgraph = { version = "0.5", default-features = false }
-prost = { version = "0.6.1", path = ".." }
-prost-types = { version = "0.6.1", path = "../prost-types" }
+prost = { version = "0.6.1", path = "..", default-features = false }
+prost-types = { version = "0.6.1", path = "../prost-types", default-features = false }
 tempfile = "3"
 
 [build-dependencies]

prost-build/src/code_generator.rs

@@ -330,6 +330,7 @@ impl<'a> CodeGenerator<'a> {
         if boxed {
             self.buf.push_str(", boxed");
         }
+
         self.buf.push_str(", tag=\"");
         self.buf.push_str(&field.number().to_string());
 
@@ -374,12 +375,12 @@ impl<'a> CodeGenerator<'a> {
         self.buf.push_str(&to_snake(field.name()));
         self.buf.push_str(": ");
         if repeated {
-            self.buf.push_str("::std::vec::Vec<");
+            self.buf.push_str("::alloc::vec::Vec<");
         } else if optional {
-            self.buf.push_str("::std::option::Option<");
+            self.buf.push_str("::core::option::Option<");
         }
         if boxed {
-            self.buf.push_str("::std::boxed::Box<");
+            self.buf.push_str("::alloc::boxed::Box<");
         }
         self.buf.push_str(&ty);
         if boxed {
@@ -416,10 +417,10 @@ impl<'a> CodeGenerator<'a> {
             .btree_map
             .iter()
             .any(|matcher| match_ident(matcher, msg_name, Some(field.name())));
-        let (annotation_ty, rust_ty) = if btree_map {
-            ("btree_map", "BTreeMap")
+        let (annotation_ty, lib_name, rust_ty) = if btree_map {
+            ("btree_map", "::alloc::collections", "BTreeMap")
         } else {
-            ("map", "HashMap")
+            ("map", "::std::collections", "HashMap")
         };
 
         let key_tag = self.field_type_tag(key);
@@ -434,8 +435,9 @@ impl<'a> CodeGenerator<'a> {
         self.append_field_attributes(msg_name, field.name());
         self.push_indent();
         self.buf.push_str(&format!(
-            "pub {}: ::std::collections::{}<{}, {}>,\n",
+            "pub {}: {}::{}<{}, {}>,\n",
             to_snake(field.name()),
+            lib_name,
             rust_ty,
             key_ty,
             value_ty
@@ -467,7 +469,7 @@ impl<'a> CodeGenerator<'a> {
         self.append_field_attributes(fq_message_name, oneof.name());
         self.push_indent();
         self.buf.push_str(&format!(
-            "pub {}: ::std::option::Option<{}>,\n",
+            "pub {}: ::core::option::Option<{}>,\n",
             to_snake(oneof.name()),
             name
         ));
@@ -528,8 +530,11 @@ impl<'a> CodeGenerator<'a> {
             );
 
             if boxed {
-                self.buf
-                    .push_str(&format!("{}(Box<{}>),\n", to_upper_camel(field.name()), ty));
+                self.buf.push_str(&format!(
+                    "{}(::alloc::boxed::Box<{}>),\n",
+                    to_upper_camel(field.name()),
+                    ty
+                ));
             } else {
                 self.buf
                     .push_str(&format!("{}({}),\n", to_upper_camel(field.name()), ty));
@@ -721,8 +726,8 @@ 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 => String::from("std::string::String"),
-            Type::Bytes => String::from("std::vec::Vec<u8>"),
+            Type::String => String::from("::alloc::string::String"),
+            Type::Bytes => String::from("::alloc::vec::Vec<u8>"),
             Type::Group | Type::Message => self.resolve_ident(field.type_name()),
         }
     }

prost-build/src/lib.rs

@@ -547,7 +547,10 @@ impl Config {
         }
 
         let buf = fs::read(descriptor_set)?;
-        let descriptor_set = FileDescriptorSet::decode(&*buf)?;
+        // Manually map error, because in no_std mode, prost::DecodeError will not implement
+        // Into<io::Error>
+        let descriptor_set = FileDescriptorSet::decode(&buf[..])
+            .map_err(|error| Error::new(ErrorKind::InvalidData, format!("{}", error)))?;
 
         let modules = self.generate(descriptor_set.file)?;
         for (module, content) in modules {

prost-derive/src/field/group.rs

@@ -126,7 +126,7 @@ impl Field {
 
     pub fn clear(&self, ident: TokenStream) -> TokenStream {
         match self.label {
-            Label::Optional => quote!(#ident = ::std::option::Option::None),
+            Label::Optional => quote!(#ident = ::core::option::Option::None),
             Label::Required => quote!(#ident.clear()),
             Label::Repeated => quote!(#ident.clear()),
         }

prost-derive/src/field/map.rs

@@ -272,11 +272,11 @@ impl Field {
             let insert_doc = format!("Inserts a key value pair into `{}`.", ident);
             Some(quote! {
                 #[doc=#get_doc]
-                pub fn #get(&self, key: #key_ref_ty) -> ::std::option::Option<#ty> {
+                pub fn #get(&self, key: #key_ref_ty) -> ::core::option::Option<#ty> {
                     self.#ident.get(#take_ref key).cloned().and_then(#ty::from_i32)
                 }
                 #[doc=#insert_doc]
-                pub fn #insert(&mut self, key: #key_ty, value: #ty) -> ::std::option::Option<#ty> {
+                pub fn #insert(&mut self, key: #key_ty, value: #ty) -> ::core::option::Option<#ty> {
                     self.#ident.insert(key, value as i32).and_then(#ty::from_i32)
                 }
             })
@@ -294,12 +294,18 @@ impl Field {
             MapTy::HashMap => Ident::new("HashMap", Span::call_site()),
             MapTy::BTreeMap => Ident::new("BTreeMap", Span::call_site()),
         };
+        // HashMap is in std, BTreeMap is in alloc
+        let libname = match self.map_ty {
+            MapTy::HashMap => Ident::new("std", Span::call_site()),
+            MapTy::BTreeMap => Ident::new("alloc", Span::call_site()),
+        };
+
         // A fake field for generating the debug wrapper
         let key_wrapper = fake_scalar(self.key_ty.clone()).debug(quote!(KeyWrapper));
         let key = self.key_ty.rust_type();
         let value_wrapper = self.value_ty.debug();
         let fmt = quote! {
-            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+            fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
                 #key_wrapper
                 #value_wrapper
                 let mut builder = f.debug_map();
@@ -313,17 +319,17 @@ impl Field {
             ValueTy::Scalar(ref ty) => {
                 let value = ty.rust_type();
                 quote! {
-                    struct #wrapper_name<'a>(&'a ::std::collections::#type_name<#key, #value>);
-                    impl<'a> ::std::fmt::Debug for #wrapper_name<'a> {
+                    struct #wrapper_name<'a>(&'a ::#libname::collections::#type_name<#key, #value>);
+                    impl<'a> ::core::fmt::Debug for #wrapper_name<'a> {
                         #fmt
                     }
                 }
             }
             ValueTy::Message => quote! {
-                struct #wrapper_name<'a, V: 'a>(&'a ::std::collections::#type_name<#key, V>);
-                impl<'a, V> ::std::fmt::Debug for #wrapper_name<'a, V>
+                struct #wrapper_name<'a, V: 'a>(&'a ::#libname::collections::#type_name<#key, V>);
+                impl<'a, V> ::core::fmt::Debug for #wrapper_name<'a, V>
                 where
-                    V: ::std::fmt::Debug + 'a,
+                    V: ::core::fmt::Debug + 'a,
                 {
                     #fmt
                 }

prost-derive/src/field/message.rs

@@ -126,7 +126,7 @@ impl Field {
 
     pub fn clear(&self, ident: TokenStream) -> TokenStream {
         match self.label {
-            Label::Optional => quote!(#ident = ::std::option::Option::None),
+            Label::Optional => quote!(#ident = ::core::option::Option::None),
             Label::Required => quote!(#ident.clear()),
             Label::Repeated => quote!(#ident.clear()),
         }

prost-derive/src/field/mod.rs

@@ -4,8 +4,8 @@ mod message;
 mod oneof;
 mod scalar;
 
-use std::fmt;
-use std::slice;
+use core::fmt;
+use core::slice;
 
 use anyhow::{bail, Error};
 use proc_macro2::TokenStream;
@@ -135,7 +135,7 @@ impl Field {
     pub fn default(&self) -> TokenStream {
         match *self {
             Field::Scalar(ref scalar) => scalar.default(),
-            _ => quote!(::std::default::Default::default()),
+            _ => quote!(::core::default::Default::default()),
         }
     }
 

prost-derive/src/field/oneof.rs

@@ -94,6 +94,6 @@ impl Field {
     }
 
     pub fn clear(&self, ident: TokenStream) -> TokenStream {
-        quote!(#ident = ::std::option::Option::None)
+        quote!(#ident = ::core::option::Option::None)
     }
 }