fix(linter): Fix config docs for no-return-assign and unicode-bom rules. (#16260)

These rules both take string options and were incorrectly documented as objects.

```
## Configuration

This rule accepts one of the following string values:

### `"always"`

Disallow all assignments in return statements.

### `"except-parens"`

Allow assignments in return statements only if they are enclosed in parentheses.
This is the default mode.
```

```md
## Configuration

This rule accepts one of the following string values:

### `"always"`

Always require a Unicode BOM (Byte Order Mark) at the beginning of the file.

### `"never"`

Never allow a Unicode BOM (Byte Order Mark) at the beginning of the file.
This is the default option.
```

Author: connorshea

crates/oxc_linter/src/rules/eslint/no_return_assign.rs

@@ -3,27 +3,39 @@ use oxc_diagnostics::OxcDiagnostic;
 use oxc_macros::declare_oxc_lint;
 use oxc_span::{GetSpan, Span};
 use schemars::JsonSchema;
+use serde::Deserialize;
 use serde_json::Value;
 
-use crate::{AstNode, context::LintContext, rule::Rule};
+use crate::{
+    AstNode,
+    context::LintContext,
+    rule::{DefaultRuleConfig, Rule},
+};
 
 fn no_return_assign_diagnostic(span: Span, message: &'static str) -> OxcDiagnostic {
     OxcDiagnostic::warn(message)
         .with_label(span)
         .with_help("Did you mean to use `==` instead of `=`?")
 }
 
-#[derive(Debug, Default, Clone, JsonSchema)]
-#[serde(rename_all = "camelCase", default)]
-pub struct NoReturnAssign {
-    /// Whether to always disallow assignment in return statements.
-    always_disallow_assignment_in_return: bool,
+#[derive(Debug, Default, Clone, Deserialize)]
+pub struct NoReturnAssign(NoReturnAssignMode);
+
+#[derive(Debug, Default, Clone, JsonSchema, Deserialize)]
+#[serde(rename_all = "kebab-case")]
+pub enum NoReturnAssignMode {
+    /// Disallow all assignments in return statements.
+    Always,
+    /// Allow assignments in return statements only if they are enclosed in parentheses.
+    /// This is the default mode.
+    #[default]
+    ExceptParens,
 }
 
 declare_oxc_lint!(
     /// ### What it does
     ///
-    /// Disallows assignment operators in return statements
+    /// Disallows assignment operators in return statements.
     ///
     /// ### Why is this bad?
     ///
@@ -48,7 +60,7 @@ declare_oxc_lint!(
     eslint,
     style,
     pending, // TODO: add a suggestion
-    config = NoReturnAssign,
+    config = NoReturnAssignMode,
 );
 
 fn is_sentinel_node(ast_kind: AstKind) -> bool {
@@ -61,18 +73,18 @@ fn is_sentinel_node(ast_kind: AstKind) -> bool {
 
 impl Rule for NoReturnAssign {
     fn from_configuration(value: Value) -> Self {
-        let always_disallow_assignment_in_return = value
-            .get(0)
-            .and_then(Value::as_str)
-            .map_or_else(|| false, |value| value != "except-parens");
-        Self { always_disallow_assignment_in_return }
+        serde_json::from_value::<DefaultRuleConfig<NoReturnAssign>>(value)
+            .unwrap_or_default()
+            .into_inner()
     }
 
     fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
         let AstKind::AssignmentExpression(assign) = node.kind() else {
             return;
         };
-        if !self.always_disallow_assignment_in_return
+
+        // Skip if mode is ExceptParens and the assignment is parenthesized
+        if matches!(self.0, NoReturnAssignMode::ExceptParens)
             && ctx.nodes().parent_kind(node.id()).as_parenthesized_expression().is_some()
         {
             return;

crates/oxc_linter/src/rules/eslint/unicode_bom.rs

@@ -4,7 +4,10 @@ use oxc_span::{SPAN, Span};
 use schemars::JsonSchema;
 use serde::Deserialize;
 
-use crate::{context::LintContext, rule::Rule};
+use crate::{
+    context::LintContext,
+    rule::{DefaultRuleConfig, Rule},
+};
 
 fn unexpected_unicode_bom_diagnostic(span: Span) -> OxcDiagnostic {
     OxcDiagnostic::warn("Unexpected Unicode BOM (Byte Order Mark)")
@@ -18,11 +21,18 @@ fn expected_unicode_bom_diagnostic(span: Span) -> OxcDiagnostic {
         .with_label(span)
 }
 
+#[derive(Debug, Default, Clone, Deserialize)]
+pub struct UnicodeBom(BomOptionType);
+
 #[derive(Debug, Default, Clone, Deserialize, JsonSchema)]
-#[serde(rename_all = "camelCase", default)]
-pub struct UnicodeBom {
-    /// Configuration option to specify whether to require or disallow Unicode BOM.
-    bom_option: BomOptionType,
+#[serde(rename_all = "kebab-case")]
+enum BomOptionType {
+    /// Always require a Unicode BOM (Byte Order Mark) at the beginning of the file.
+    Always,
+    /// Never allow a Unicode BOM (Byte Order Mark) at the beginning of the file.
+    /// This is the default option.
+    #[default]
+    Never,
 }
 
 declare_oxc_lint!(
@@ -48,63 +58,43 @@ declare_oxc_lint!(
     eslint,
     restriction,
     fix,
-    config = UnicodeBom,
+    config = BomOptionType,
 );
 
 impl Rule for UnicodeBom {
     fn from_configuration(value: serde_json::Value) -> Self {
-        let obj = value.get(0);
-
-        Self {
-            bom_option: obj
-                .and_then(serde_json::Value::as_str)
-                .map(BomOptionType::from)
-                .unwrap_or_default(),
-        }
+        serde_json::from_value::<DefaultRuleConfig<UnicodeBom>>(value)
+            .unwrap_or_default()
+            .into_inner()
     }
 
     fn run_once(&self, ctx: &LintContext) {
         let source = ctx.source_text();
         let has_bomb = source.starts_with('');
 
-        if has_bomb && matches!(self.bom_option, BomOptionType::Never) {
+        if has_bomb && matches!(self.0, BomOptionType::Never) {
             ctx.diagnostic_with_fix(unexpected_unicode_bom_diagnostic(SPAN), |fixer| {
                 fixer.delete_range(Span::new(0, 3))
             });
         }
 
-        if !has_bomb && matches!(self.bom_option, BomOptionType::Always) {
+        if !has_bomb && matches!(self.0, BomOptionType::Always) {
             ctx.diagnostic_with_fix(expected_unicode_bom_diagnostic(SPAN), |fixer| {
                 fixer.replace(SPAN, "")
             });
         }
     }
 }
 
-#[derive(Debug, Default, Clone, Deserialize, JsonSchema)]
-#[serde(rename_all = "kebab-case")]
-enum BomOptionType {
-    Always,
-    #[default]
-    Never,
-}
-
-impl BomOptionType {
-    pub fn from(raw: &str) -> Self {
-        match raw {
-            "always" => Self::Always,
-            _ => Self::Never,
-        }
-    }
-}
-
 #[test]
 fn test() {
     use crate::tester::Tester;
 
     let pass = vec![
         (" var a = 123;", Some(serde_json::json!(["always"]))),
         ("var a = 123;", Some(serde_json::json!(["never"]))),
+        // Ensure default config works
+        ("var a = 123;", None),
         ("var a = 123; ", Some(serde_json::json!(["never"]))),
     ];