feat(linter): eslint-plugin-unicorn require-array-join-separator(style)

crates/oxc_linter/src/rules.rs

@@ -205,6 +205,7 @@ mod unicorn {
     pub mod prefer_string_starts_ends_with;
     pub mod prefer_string_trim_start_end;
     pub mod prefer_type_error;
+    pub mod require_array_join_separator;
     pub mod require_number_to_fixed_digits_argument;
     pub mod switch_case_braces;
     pub mod text_encoding_identifier_case;
@@ -385,6 +386,7 @@ oxc_macros::declare_all_lint_rules! {
     unicorn::prefer_string_starts_ends_with,
     unicorn::prefer_string_trim_start_end,
     unicorn::prefer_type_error,
+    unicorn::require_array_join_separator,
     unicorn::require_number_to_fixed_digits_argument,
     unicorn::switch_case_braces,
     unicorn::text_encoding_identifier_case,

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

@@ -0,0 +1,182 @@
+use oxc_ast::{
+    ast::{Expression, MemberExpression},
+    AstKind,
+};
+use oxc_diagnostics::{
+    miette::{self, Diagnostic},
+    thiserror::Error,
+};
+use oxc_macros::declare_oxc_lint;
+use oxc_span::{GetSpan, Span};
+
+use crate::{ast_util::is_method_call, context::LintContext, rule::Rule, AstNode};
+
+#[derive(Debug, Error, Diagnostic)]
+#[error("eslint-plugin-unicorn(require-array-join-separator): Enforce using the separator argument with Array#join()")]
+#[diagnostic(severity(warning), help("Missing the separator argument."))]
+struct RequireArrayJoinSeparatorDiagnostic(#[label] pub Span);
+
+#[derive(Debug, Default, Clone)]
+pub struct RequireArrayJoinSeparator;
+
+declare_oxc_lint!(
+    /// ### What it does
+    ///
+    /// Enforce using the separator argument with Array#join()
+    ///
+    /// ### Why is this bad?
+    ///
+    /// It's better to make it clear what the separator is when calling Array#join(),
+    /// instead of relying on the default comma (',') separator.
+    ///
+    /// ### Example
+    /// ```javascript
+    /// // Bad
+    /// foo.join()
+    ///
+    /// // Good
+    /// foo.join(",")
+    /// ```
+    RequireArrayJoinSeparator,
+    style
+);
+
+// ref: https://github.com/sindresorhus/eslint-plugin-unicorn/blob/main/rules/utils/array-or-object-prototype-property.js
+fn is_prototype_property(
+    member_expr: &MemberExpression,
+    property: &str,
+    object: Option<&str>,
+) -> bool {
+    if !member_expr.static_property_name().is_some_and(|name| name == property)
+        || member_expr.optional()
+    {
+        return false;
+    }
+
+    // `Object.prototype.method` or `Array.prototype.method`
+    if let Expression::MemberExpression(member_expr_obj) = member_expr.object() {
+        if let Expression::Identifier(iden) = member_expr_obj.object() {
+            if member_expr_obj.static_property_name().is_some_and(|name| name == "prototype")
+                && object.is_some_and(|val| val == iden.name)
+                && !member_expr.optional()
+                && !member_expr_obj.optional()
+            {
+                return true;
+            }
+        }
+    };
+
+    match object {
+        // `[].method`
+        Some("Array") => {
+            if let Expression::ArrayExpression(array_expr) = member_expr.object() {
+                array_expr.elements.len() == 0
+            } else {
+                false
+            }
+        }
+
+        // `{}.method`
+        Some("Object") => {
+            if let Expression::ObjectExpression(obj_expr) = member_expr.object() {
+                obj_expr.properties.len() == 0
+            } else {
+                false
+            }
+        }
+        _ => false,
+    }
+}
+
+fn is_array_prototype_property(member_expr: &MemberExpression, property: &str) -> bool {
+    is_prototype_property(member_expr, property, Some("Array"))
+}
+
+impl Rule for RequireArrayJoinSeparator {
+    fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
+        let AstKind::CallExpression(call_expr) = node.kind() else {
+            return;
+        };
+
+        let Some(member_expr) = call_expr.callee.get_member_expr() else {
+            return;
+        };
+
+        // foo.join()
+        if is_method_call(call_expr, None, Some(&["join"]), Some(0), Some(0))
+            && !call_expr.optional
+            && !matches!(member_expr, MemberExpression::ComputedMemberExpression(_))
+        {
+            ctx.diagnostic(RequireArrayJoinSeparatorDiagnostic(Span {
+                start: member_expr.span().end,
+                end: call_expr.span.end,
+            }));
+        }
+
+        // `[].join.call(foo)` and `Array.prototype.join.call(foo)`
+        if let Expression::MemberExpression(member_expr_obj) = member_expr.object() {
+            if is_method_call(call_expr, None, Some(&["call"]), Some(1), Some(1))
+                && !member_expr.optional()
+                && !call_expr.optional
+                && !call_expr.arguments.iter().any(oxc_ast::ast::Argument::is_spread)
+                && is_array_prototype_property(member_expr_obj, "join")
+            {
+                ctx.diagnostic(RequireArrayJoinSeparatorDiagnostic(Span {
+                    start: member_expr.span().end,
+                    end: call_expr.span.end,
+                }));
+            }
+        }
+    }
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        ("foo.join(\",\")", None),
+        (r"join()", None),
+        (r"foo.join(...[])", None),
+        (r"foo.join?.()", None),
+        (r"foo?.join?.()", None),
+        (r"foo[join]()", None),
+        ("foo[\"join\"]()", None),
+        ("[].join.call(foo, \",\")", None),
+        (r"[].join.call()", None),
+        (r"[].join.call(...[foo])", None),
+        (r"[].join?.call(foo)", None),
+        (r"[]?.join.call(foo)", None),
+        (r"[].join[call](foo)", None),
+        (r"[][join].call(foo)", None),
+        (r"[,].join.call(foo)", None),
+        (r"[].join.notCall(foo)", None),
+        (r"[].notJoin.call(foo)", None),
+        ("Array.prototype.join.call(foo, \"\")", None),
+        (r"Array.prototype.join.call()", None),
+        (r"Array.prototype.join.call(...[foo])", None),
+        (r"Array.prototype.join?.call(foo)", None),
+        (r"Array.prototype?.join.call(foo)", None),
+        (r"Array?.prototype.join.call(foo)", None),
+        ("Array.prototype.join[call](foo, \"\")", None),
+        (r"Array.prototype[join].call(foo)", None),
+        (r"Array[prototype].join.call(foo)", None),
+        (r"Array.prototype.join.notCall(foo)", None),
+        (r"Array.prototype.notJoin.call(foo)", None),
+        (r"Array.notPrototype.join.call(foo)", None),
+        (r"NotArray.prototype.join.call(foo)", None),
+        ("path.join(__dirname, \"./foo.js\")", None),
+    ];
+
+    let fail = vec![
+        (r"foo.join()", None),
+        (r"[].join.call(foo)", None),
+        (r"[].join.call(foo,)", None),
+        (r"[].join.call(foo , );", None),
+        (r"Array.prototype.join.call(foo)", None),
+        (r"Array.prototype.join.call(foo, )", None),
+        (r"foo?.join()", None),
+    ];
+
+    Tester::new(RequireArrayJoinSeparator::NAME, pass, fail).test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/require_array_join_separator.snap

@@ -0,0 +1,54 @@
+---
+source: crates/oxc_linter/src/tester.rs
+expression: require_array_join_separator
+---
+  ⚠ eslint-plugin-unicorn(require-array-join-separator): Enforce using the separator argument with Array#join()
+   ╭─[require_array_join_separator.tsx:1:1]
+ 1 │ foo.join()
+   ·         ──
+   ╰────
+  help: Missing the separator argument.
+
+  ⚠ eslint-plugin-unicorn(require-array-join-separator): Enforce using the separator argument with Array#join()
+   ╭─[require_array_join_separator.tsx:1:1]
+ 1 │ [].join.call(foo)
+   ·             ─────
+   ╰────
+  help: Missing the separator argument.
+
+  ⚠ eslint-plugin-unicorn(require-array-join-separator): Enforce using the separator argument with Array#join()
+   ╭─[require_array_join_separator.tsx:1:1]
+ 1 │ [].join.call(foo,)
+   ·             ──────
+   ╰────
+  help: Missing the separator argument.
+
+  ⚠ eslint-plugin-unicorn(require-array-join-separator): Enforce using the separator argument with Array#join()
+   ╭─[require_array_join_separator.tsx:1:1]
+ 1 │ [].join.call(foo , );
+   ·             ────────
+   ╰────
+  help: Missing the separator argument.
+
+  ⚠ eslint-plugin-unicorn(require-array-join-separator): Enforce using the separator argument with Array#join()
+   ╭─[require_array_join_separator.tsx:1:1]
+ 1 │ Array.prototype.join.call(foo)
+   ·                          ─────
+   ╰────
+  help: Missing the separator argument.
+
+  ⚠ eslint-plugin-unicorn(require-array-join-separator): Enforce using the separator argument with Array#join()
+   ╭─[require_array_join_separator.tsx:1:1]
+ 1 │ Array.prototype.join.call(foo, )
+   ·                          ───────
+   ╰────
+  help: Missing the separator argument.
+
+  ⚠ eslint-plugin-unicorn(require-array-join-separator): Enforce using the separator argument with Array#join()
+   ╭─[require_array_join_separator.tsx:1:1]
+ 1 │ foo?.join()
+   ·          ──
+   ╰────
+  help: Missing the separator argument.
+
+