Extern function to generate metadata (#460)

* Hack to see if #[start] works

* Hack to see if #[no_mangle] works

* Remove incrementer bin target

* Use Rust extern api and pass back InkProject struct directly

* Uglify name

* Update remaining examples to use generate metadata function

* Do not generate for ink-as-dependency to make delegator work

* Remove explicit version from abi dependency

* Remove duplication

* Remove GenerateAbi trait

examples/delegator/.ink/abi_gen/Cargo.toml

@@ -10,6 +10,7 @@ name = "abi-gen"
 path = "main.rs"
 
 [dependencies]
+ink_abi = { path = "../../../../abi" }
 contract = { path = "../..", package = "delegator" }
 ink_lang = { path = "../../../../lang" }
 serde = "1.0"

examples/delegator/.ink/abi_gen/main.rs

+extern crate contract;
+
+extern "Rust" {
+    fn __ink_generate_metadata() -> ink_abi::InkProject;
+}
+
 fn main() -> Result<(), std::io::Error> {
-    let abi = <::contract::Delegator as ::ink_lang::GenerateAbi>::generate_abi();
-    let contents = serde_json::to_string_pretty(&abi)?;
+    let ink_project = unsafe { __ink_generate_metadata() };
+    let contents = serde_json::to_string_pretty(&ink_project)?;
     std::fs::create_dir("target").ok();
     std::fs::write("target/metadata.json", contents)?;
     Ok(())

examples/dns/.ink/abi_gen/Cargo.toml

@@ -10,6 +10,7 @@ name = "abi-gen"
 path = "main.rs"
 
 [dependencies]
+ink_abi = { path = "../../../../abi" }
 contract = { path = "../..", package = "dns" }
 ink_lang = { path = "../../../../lang" }
 serde = "1.0"

examples/dns/.ink/abi_gen/main.rs

+extern crate contract;
+
+extern "Rust" {
+    fn __ink_generate_metadata() -> ink_abi::InkProject;
+}
+
 fn main() -> Result<(), std::io::Error> {
-    let abi = <::contract::DomainNameService as ::ink_lang::GenerateAbi>::generate_abi();
-    let contents = serde_json::to_string_pretty(&abi)?;
+    let ink_project = unsafe { __ink_generate_metadata() };
+    let contents = serde_json::to_string_pretty(&ink_project)?;
     std::fs::create_dir("target").ok();
     std::fs::write("target/metadata.json", contents)?;
     Ok(())

examples/erc20/.ink/abi_gen/Cargo.toml

@@ -10,6 +10,7 @@ name = "abi-gen"
 path = "main.rs"
 
 [dependencies]
+ink_abi = { path = "../../../../abi" }
 contract = { path = "../..", package = "erc20" }
 ink_lang = { path = "../../../../lang" }
 serde = "1.0"

examples/erc20/.ink/abi_gen/main.rs

+extern crate contract;
+
+extern "Rust" {
+    fn __ink_generate_metadata() -> ink_abi::InkProject;
+}
+
 fn main() -> Result<(), std::io::Error> {
-    let abi = <::contract::Erc20 as ::ink_lang::GenerateAbi>::generate_abi();
-    let contents = serde_json::to_string_pretty(&abi)?;
+    let ink_project = unsafe { __ink_generate_metadata() };
+    let contents = serde_json::to_string_pretty(&ink_project)?;
     std::fs::create_dir("target").ok();
     std::fs::write("target/metadata.json", contents)?;
     Ok(())

examples/erc721/.ink/abi_gen/Cargo.toml

@@ -10,6 +10,7 @@ name = "abi-gen"
 path = "main.rs"
 
 [dependencies]
+ink_abi = { path = "../../../../abi" }
 contract = { path = "../..", package = "erc721" }
 ink_lang = { path = "../../../../lang" }
 serde = "1.0"

examples/erc721/.ink/abi_gen/main.rs

+extern crate contract;
+
+extern "Rust" {
+    fn __ink_generate_metadata() -> ink_abi::InkProject;
+}
+
 fn main() -> Result<(), std::io::Error> {
-    let abi = <::contract::Erc721 as ::ink_lang::GenerateAbi>::generate_abi();
-    let contents = serde_json::to_string_pretty(&abi)?;
+    let ink_project = unsafe { __ink_generate_metadata() };
+    let contents = serde_json::to_string_pretty(&ink_project)?;
     std::fs::create_dir("target").ok();
     std::fs::write("target/metadata.json", contents)?;
     Ok(())

examples/flipper/.ink/abi_gen/Cargo.toml

@@ -10,6 +10,7 @@ name = "abi-gen"
 path = "main.rs"
 
 [dependencies]
+ink_abi = { path = "../../../../abi" }
 contract = { path = "../..", package = "flipper" }
 ink_lang = { path = "../../../../lang" }
 serde = "1.0"

examples/flipper/.ink/abi_gen/main.rs

+extern crate contract;
+
+extern "Rust" {
+    fn __ink_generate_metadata() -> ink_abi::InkProject;
+}
+
 fn main() -> Result<(), std::io::Error> {
-    let abi = <::contract::Flipper as ::ink_lang::GenerateAbi>::generate_abi();
-    let contents = serde_json::to_string_pretty(&abi)?;
+    let ink_project = unsafe { __ink_generate_metadata() };
+    let contents = serde_json::to_string_pretty(&ink_project)?;
     std::fs::create_dir("target").ok();
     std::fs::write("target/metadata.json", contents)?;
     Ok(())

examples/incrementer/.ink/abi_gen/Cargo.toml

@@ -10,6 +10,7 @@ name = "abi-gen"
 path = "main.rs"
 
 [dependencies]
+ink_abi = { path = "../../../../abi" }
 contract = { path = "../..", package = "incrementer" }
 ink_lang = { path = "../../../../lang" }
 serde = "1.0"

examples/incrementer/.ink/abi_gen/main.rs

+extern crate contract;
+
+extern "Rust" {
+    fn __ink_generate_metadata() -> ink_abi::InkProject;
+}
+
 fn main() -> Result<(), std::io::Error> {
-    let abi = <::contract::Incrementer as ::ink_lang::GenerateAbi>::generate_abi();
-    let contents = serde_json::to_string_pretty(&abi)?;
+    let ink_project = unsafe { __ink_generate_metadata() };
+    let contents = serde_json::to_string_pretty(&ink_project)?;
     std::fs::create_dir("target").ok();
     std::fs::write("target/metadata.json", contents)?;
     Ok(())

examples/multisig_plain/.ink/abi_gen/Cargo.toml

@@ -10,6 +10,7 @@ name = "abi-gen"
 path = "main.rs"
 
 [dependencies]
+ink_abi = { path = "../../../../abi" }
 contract = { path = "../..", package = "multisig_plain" }
 ink_lang = { path = "../../../../lang", package = "ink_lang" }
 serde = "1.0"

examples/multisig_plain/.ink/abi_gen/main.rs

+extern crate contract;
+
+extern "Rust" {
+    fn __ink_generate_metadata() -> ink_abi::InkProject;
+}
+
 fn main() -> Result<(), std::io::Error> {
-    let abi = <::contract::MultisigPlain as ::ink_lang::GenerateAbi>::generate_abi();
-    let contents = serde_json::to_string_pretty(&abi)?;
+    let ink_project = unsafe { __ink_generate_metadata() };
+    let contents = serde_json::to_string_pretty(&ink_project)?;
     std::fs::create_dir("target").ok();
     std::fs::write("target/metadata.json", contents)?;
     Ok(())

examples/runtime-storage/.ink/abi_gen/Cargo.toml

@@ -10,6 +10,7 @@ name = "abi-gen"
 path = "main.rs"
 
 [dependencies]
+ink_abi = { path = "../../../../abi" }
 contract = { path = "../..", package = "runtime_storage" }
 ink_lang = { path = "../../../../lang" }
 serde = "1.0"

examples/runtime-storage/.ink/abi_gen/main.rs

+extern crate contract;
+
+extern "Rust" {
+    fn __ink_generate_metadata() -> ink_abi::InkProject;
+}
+
 fn main() -> Result<(), std::io::Error> {
-    let abi = <::contract::RuntimeStorage as ::ink_lang::GenerateAbi>::generate_abi();
-    let contents = serde_json::to_string_pretty(&abi)?;
+    let ink_project = unsafe { __ink_generate_metadata() };
+    let contents = serde_json::to_string_pretty(&ink_project)?;
     std::fs::create_dir("target").ok();
     std::fs::write("target/metadata.json", contents)?;
     Ok(())

lang/macro/src/codegen/abi.rs

@@ -34,16 +34,15 @@ pub struct GenerateAbi<'a> {
 
 impl GenerateCode for GenerateAbi<'_> {
     fn generate_code(&self) -> TokenStream2 {
-        let storage_ident = &self.contract.storage.ident;
-
         let contract = self.generate_contract();
         let layout = self.generate_layout();
 
         quote! {
             #[cfg(feature = "std")]
+            #[cfg(not(feature = "ink-as-dependency"))]
             const _: () = {
-                impl ::ink_lang::GenerateAbi for #storage_ident {
-                    fn generate_abi() -> ::ink_abi::InkProject {
+                #[no_mangle]
+                pub fn __ink_generate_metadata() -> ::ink_abi::InkProject  {
                     let contract: ::ink_abi::ContractSpec = {
                         #contract
                     };
@@ -52,7 +51,6 @@ impl GenerateCode for GenerateAbi<'_> {
                     };
                     ::ink_abi::InkProject::new(layout, contract)
                 }
-                }
             };
         }
     }

lang/src/abi.rs

-// Copyright 2018-2019 Parity Technologies (UK) Ltd.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-/// Types implementing this trait can generate their metadata.
-pub trait GenerateAbi {
-    /// Generates the virtual ABI (metadata).
-    fn generate_abi() -> ink_abi::InkProject;
-}

lang/src/lib.rs

@@ -14,9 +14,6 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
-#[cfg(feature = "std")]
-mod abi;
-
 mod contract;
 mod cross_calling;
 mod dispatcher;
@@ -27,9 +24,6 @@ mod traits;
 
 pub use ink_lang_macro::contract;
 
-#[cfg(feature = "std")]
-pub use self::abi::GenerateAbi;
-
 pub use self::{
     contract::{
         DispatchMode,