feat(linter): implement unicorn/no-unnecessary-await (#856)

related to #684

crates/oxc_linter/src/rules.rs

@@ -103,6 +103,7 @@ mod jest {
 
 mod unicorn {
     pub mod no_instanceof_array;
+    pub mod no_unnecessary_await;
 }
 
 oxc_macros::declare_all_lint_rules! {
@@ -191,4 +192,5 @@ oxc_macros::declare_all_lint_rules! {
     jest::no_alias_methods,
     jest::no_conditional_expect,
     unicorn::no_instanceof_array,
+    unicorn::no_unnecessary_await
 }

crates/oxc_linter/src/rules/unicorn/no_unnecessary_await.rs

@@ -0,0 +1,162 @@
+use oxc_ast::{ast::Expression, AstKind};
+use oxc_diagnostics::{
+    miette::{self, Diagnostic},
+    thiserror::Error,
+};
+use oxc_formatter::Gen;
+use oxc_macros::declare_oxc_lint;
+use oxc_span::Span;
+
+use crate::{context::LintContext, rule::Rule, AstNode, Fix};
+
+#[derive(Debug, Error, Diagnostic)]
+#[error("Disallow awaiting non-promise values.")]
+#[diagnostic(severity(warning), help("consider to remove the `await`"))]
+struct NoUnnecessaryAwaitDiagnostic(#[label] pub Span);
+
+#[derive(Debug, Default, Clone)]
+pub struct NoUnnecessaryAwait;
+
+declare_oxc_lint!(
+    /// ### What it does
+    /// Disallow awaiting on non-promise values.
+    ///
+    /// ### Why is this bad?
+    /// The `await` operator should only be used on `Promise` values.
+    ///
+    /// ### Example
+    /// ```javascript
+    /// await await promise;
+    /// ```
+    NoUnnecessaryAwait,
+    correctness
+);
+
+impl Rule for NoUnnecessaryAwait {
+    fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
+        if let AstKind::AwaitExpression(expr) = node.kind() {
+            if !not_promise(&expr.argument) {
+                return;
+            }
+            if {
+                // Removing `await` may change them to a declaration, if there is no `id` will cause SyntaxError
+                matches!(expr.argument, Expression::FunctionExpression(_))
+                    || matches!(expr.argument, Expression::ClassExpression(_))
+            } || {
+                // `+await +1` -> `++1`
+                ctx.nodes().parent_node(node.id()).map_or(false, |parent| {
+                    if let (
+                        AstKind::UnaryExpression(parent_unary),
+                        Expression::UnaryExpression(inner_unary),
+                    ) = (parent.kind(), &expr.argument)
+                    {
+                        parent_unary.operator == inner_unary.operator
+                    } else {
+                        false
+                    }
+                })
+            } {
+                ctx.diagnostic(NoUnnecessaryAwaitDiagnostic(expr.span));
+            } else {
+                ctx.diagnostic_with_fix(NoUnnecessaryAwaitDiagnostic(expr.span), || {
+                    let mut formatter = ctx.formatter();
+                    expr.argument.gen(&mut formatter);
+                    Fix::new(formatter.into_code(), expr.span)
+                });
+            };
+        }
+    }
+}
+
+fn not_promise(expr: &Expression) -> bool {
+    match expr {
+        Expression::ArrayExpression(_)
+        | Expression::ArrowExpression(_)
+        | Expression::AwaitExpression(_)
+        | Expression::BinaryExpression(_)
+        | Expression::ClassExpression(_)
+        | Expression::FunctionExpression(_)
+        | Expression::JSXElement(_)
+        | Expression::JSXFragment(_)
+        | Expression::BooleanLiteral(_)
+        | Expression::NullLiteral(_)
+        | Expression::NumberLiteral(_)
+        | Expression::BigintLiteral(_)
+        | Expression::RegExpLiteral(_)
+        | Expression::StringLiteral(_)
+        | Expression::TemplateLiteral(_)
+        | Expression::UnaryExpression(_)
+        | Expression::UpdateExpression(_) => true,
+        Expression::SequenceExpression(expr) => not_promise(expr.expressions.last().unwrap()),
+        Expression::ParenthesizedExpression(expr) => not_promise(&expr.expression),
+        _ => false,
+    }
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        ("await {then}", None),
+        ("await a ? b : c", None),
+        ("await a || b", None),
+        ("await a && b", None),
+        ("await a ?? b", None),
+        ("await new Foo()", None),
+        ("await tagged``", None),
+        ("class A { async foo() { await this }}", None),
+        ("async function * foo() {await (yield bar);}", None),
+        ("await (1, Promise.resolve())", None),
+    ];
+
+    let fail = vec![
+        ("await []", None),
+        ("await [Promise.resolve()]", None),
+        ("await (() => {})", None),
+        ("await (() => Promise.resolve())", None),
+        ("await (a === b)", None),
+        ("await (a instanceof Promise)", None),
+        ("await (a > b)", None),
+        ("await class {}", None),
+        ("await class extends Promise {}", None),
+        ("await function() {}", None),
+        ("await function name() {}", None),
+        ("await function() { return Promise.resolve() }", None),
+        ("await (<></>)", None),
+        ("await (<a></a>)", None),
+        ("await 0", None),
+        ("await 1", None),
+        ("await \"\"", None),
+        ("await \"string\"", None),
+        ("await true", None),
+        ("await false", None),
+        ("await null", None),
+        ("await 0n", None),
+        ("await 1n", None),
+        ("await `${Promise.resolve()}`", None),
+        ("await !Promise.resolve()", None),
+        ("await void Promise.resolve()", None),
+        ("await +Promise.resolve()", None),
+        ("await ~1", None),
+        ("await ++foo", None),
+        ("await foo--", None),
+        ("await (Promise.resolve(), 1)", None),
+        ("async function foo() {+await +1}", None),
+        ("async function foo() {-await-1}", None),
+        ("async function foo() {+await -1}", None),
+    ];
+
+    let fix = vec![
+        ("await []", "[]", None),
+        ("await (a == b)", "(a == b)", None),
+        ("+await -1", "+ -1", None),
+        ("-await +1", "- +1", None),
+        ("await function() {}", "await function() {}", None), // no autofix
+        ("await class {}", "await class {}", None),           // no autofix
+        ("+await +1", "+await +1", None),                     // no autofix
+        ("-await -1", "-await -1", None),                     // no autofix
+    ];
+
+    Tester::new(NoUnnecessaryAwait::NAME, pass, fail).expect_fix(fix).test_and_snapshot();
+}