Add no_main lint

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Linter: `storage_never_freed` lint - [#1932](https://github.com/paritytech/ink/pull/1932)
 - Linter: `strict_balance_equality` lint - [#1914](https://github.com/paritytech/ink/pull/1914)
+- Linter: `no_main` lint - [#2001](https://github.com/paritytech/ink/pull/2001)
 
 ## Version 5.0.0-alpha
 

linting/Cargo.toml

@@ -63,6 +63,9 @@ path = "ui/pass/strict_balance_equality.rs"
 [[example]]
 name = "strict_balance_equality_fail"
 path = "ui/fail/strict_balance_equality.rs"
+[[example]]
+name = "no_main_pass"
+path = "ui/pass/no_main.rs"
 
 [package.metadata.rust-analyzer]
 rustc_private = true

linting/src/lib.rs

@@ -32,6 +32,7 @@ extern crate rustc_session;
 extern crate rustc_span;
 
 mod ink_utils;
+mod no_main;
 mod primitive_topic;
 mod storage_never_freed;
 mod strict_balance_equality;
@@ -46,11 +47,13 @@ pub fn register_lints(
         primitive_topic::PRIMITIVE_TOPIC,
         storage_never_freed::STORAGE_NEVER_FREED,
         strict_balance_equality::STRICT_BALANCE_EQUALITY,
+        no_main::NO_MAIN,
     ]);
     lint_store.register_late_pass(|_| Box::new(primitive_topic::PrimitiveTopic));
     lint_store.register_late_pass(|_| Box::new(storage_never_freed::StorageNeverFreed));
     lint_store
         .register_late_pass(|_| Box::new(strict_balance_equality::StrictBalanceEquality));
+    lint_store.register_early_pass(|| Box::new(no_main::NoMain));
 }
 
 #[test]

linting/src/no_main.rs

@@ -0,0 +1,98 @@
+// Copyright (C) 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.
+
+use ast::{
+    AttrStyle,
+    Crate,
+};
+use clippy_utils::diagnostics::span_lint_and_help;
+use if_chain::if_chain;
+use rustc_ast as ast;
+use rustc_lint::{
+    EarlyContext,
+    EarlyLintPass,
+    LintContext,
+};
+use rustc_middle::lint::in_external_macro;
+use rustc_session::{
+    declare_lint,
+    declare_lint_pass,
+};
+use rustc_span::sym;
+
+declare_lint! {
+    /// ## What it does
+    /// Checks if a contract is annotated with the `no_main` inner attribute.
+    ///
+    /// ## Why is this necessary?
+    /// Contracts must be annotated with `no_main` inner attribute when compiled for on-chain
+    /// execution.
+    ///
+    /// ## Example
+    ///
+    /// ```rust
+    /// // Bad: Contract does not contain the `no_main` attribute, so it cannot be compiled to Wasm
+    /// #![cfg_attr(not(feature = "std"), no_std)]
+    ///	#[ink::contract]
+    ///	mod my_contract { /* ... */ }
+    /// ```
+    ///
+    /// Use instead:
+    ///
+    /// ```rust
+    /// #![cfg_attr(not(feature = "std"), no_std, no_main)]
+    ///	#[ink::contract]
+    ///	mod my_contract { /* ... */ }
+    /// ```
+    pub NO_MAIN,
+    Deny,
+    "contract must be annotated with the `no_main` inner attribute"
+}
+
+declare_lint_pass!(NoMain => [NO_MAIN]);
+
+/// Returns true if the target architecture is suitable to be executed on-chain
+fn is_contract_build(cx: &EarlyContext<'_>) -> bool {
+    matches!(
+        cx.sess().target.llvm_target.to_string().as_str(),
+        "wasm32-unknown-unknown" | "riscv32i-unknown-none-elf"
+    )
+}
+
+impl EarlyLintPass for NoMain {
+    fn check_crate(&mut self, cx: &EarlyContext<'_>, krate: &Crate) {
+        // Disable when building for e2e tests
+        if !is_contract_build(cx) {
+            return
+        }
+
+        // `no_main` is an `Inner` attribute of `#![cfg_attr(...)]`
+        if krate.attrs.iter().all(|attr| {
+            if_chain! {
+            if !in_external_macro(cx.sess(), attr.span);
+            if let AttrStyle::Inner = attr.style;
+            if attr.has_name(sym::no_main);
+            then { false } else { true }}
+        }) {
+            span_lint_and_help(
+                cx,
+                NO_MAIN,
+                krate.spans.inner_span,
+                "contract must be annotated with the `no_main` inner attribute",
+                None,
+                "consider annotating contract with `#![cfg_attr(not(feature = \"std\"), no_std, no_main)]` or `#![no_main]`"
+            )
+        }
+    }
+}

linting/ui/pass/no_main.rs

@@ -0,0 +1,17 @@
+#![cfg_attr(not(feature = "std"), no_std, no_main)]
+
+#[ink::contract]
+pub mod no_main {
+    #[ink(storage)]
+    pub struct NoMain {}
+    impl NoMain {
+        #[ink(constructor)]
+        pub fn new() -> Self {
+            Self {}
+        }
+        #[ink(message)]
+        pub fn do_nothing(&mut self) {}
+    }
+}
+
+fn main() {}