feat(linter): implement useExplicitFunctionReturnType

crates/biome_cli/tests/snapshots/main_commands_check/top_level_all_down_level_not_all.snap

@@ -40,6 +40,25 @@ check ━━━━━━━━━━━━━━━━━━━━━━━━
 
 # Emitted Messages
 
+```block
+fix.js:1:1 lint/nursery/useExplicitFunctionReturnType ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! Missing return type on function.
+
+  > 1 │ 
+      │ 
+  > 2 │     function f() {arguments;}
+      │     ^^^^^^^^^^
+    3 │     const FOO = "FOO";
+    4 │     var x, y;
+
+  i Declaring the return type makes the code self-documenting and can speed up TypeScript type checking.
+
+  i Add a return type annotation.
+
+
+```
+
 ```block
 fix.js:2:14 lint/correctness/noUnusedVariables ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
 
@@ -151,5 +170,5 @@ fix.js format ━━━━━━━━━━━━━━━━━━━━━━
 ```block
 Checked 1 file in <TIME>. No fixes applied.
 Found 1 error.
-Found 4 warnings.
+Found 5 warnings.
 ```

crates/biome_cli/tests/snapshots/main_commands_lint/top_level_all_true_group_level_all_false.snap

@@ -29,6 +29,25 @@ expression: content
 
 # Emitted Messages
 
+```block
+fix.js:1:1 lint/nursery/useExplicitFunctionReturnType ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! Missing return type on function.
+
+  > 1 │ 
+      │ 
+  > 2 │     function f() {arguments;}
+      │     ^^^^^^^^^^
+    3 │     const FOO = "FOO";
+    4 │     var x, y;
+
+  i Declaring the return type makes the code self-documenting and can speed up TypeScript type checking.
+
+  i Add a return type annotation.
+
+
+```
+
 ```block
 fix.js:2:14 lint/correctness/noUnusedVariables ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
 
@@ -119,5 +138,5 @@ fix.js:4:12 lint/correctness/noUnusedVariables  FIXABLE  ━━━━━━━
 
 ```block
 Checked 1 file in <TIME>. No fixes applied.
-Found 4 warnings.
+Found 5 warnings.
 ```

crates/biome_configuration/src/analyzer/linter/rules.rs

@@ -3368,6 +3368,10 @@ pub struct Nursery {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub use_deprecated_reason:
         Option<RuleConfiguration<biome_graphql_analyze::options::UseDeprecatedReason>>,
+    #[doc = "Require explicit return types on functions and class methods."]
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub use_explicit_function_return_type:
+        Option<RuleConfiguration<biome_js_analyze::options::UseExplicitFunctionReturnType>>,
     #[doc = "Disallows package private imports."]
     #[serde(skip_serializing_if = "Option::is_none")]
     pub use_import_restrictions:
@@ -3431,6 +3435,7 @@ impl Nursery {
         "useConsistentCurlyBraces",
         "useConsistentMemberAccessibility",
         "useDeprecatedReason",
+        "useExplicitFunctionReturnType",
         "useImportRestrictions",
         "useSortedClasses",
         "useStrictMode",
@@ -3461,7 +3466,7 @@ impl Nursery {
         RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[21]),
         RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[24]),
         RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[25]),
-        RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[28]),
+        RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[29]),
     ];
     const ALL_RULES_AS_FILTERS: &'static [RuleFilter<'static>] = &[
         RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[0]),
@@ -3495,6 +3500,7 @@ impl Nursery {
         RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[28]),
         RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[29]),
         RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[30]),
+        RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[31]),
     ];
     #[doc = r" Retrieves the recommended rules"]
     pub(crate) fn is_recommended_true(&self) -> bool {
@@ -3641,31 +3647,36 @@ impl Nursery {
                 index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[25]));
             }
         }
-        if let Some(rule) = self.use_import_restrictions.as_ref() {
+        if let Some(rule) = self.use_explicit_function_return_type.as_ref() {
             if rule.is_enabled() {
                 index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[26]));
             }
         }
-        if let Some(rule) = self.use_sorted_classes.as_ref() {
+        if let Some(rule) = self.use_import_restrictions.as_ref() {
             if rule.is_enabled() {
                 index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[27]));
             }
         }
-        if let Some(rule) = self.use_strict_mode.as_ref() {
+        if let Some(rule) = self.use_sorted_classes.as_ref() {
             if rule.is_enabled() {
                 index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[28]));
             }
         }
-        if let Some(rule) = self.use_trim_start_end.as_ref() {
+        if let Some(rule) = self.use_strict_mode.as_ref() {
             if rule.is_enabled() {
                 index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[29]));
             }
         }
-        if let Some(rule) = self.use_valid_autocomplete.as_ref() {
+        if let Some(rule) = self.use_trim_start_end.as_ref() {
             if rule.is_enabled() {
                 index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[30]));
             }
         }
+        if let Some(rule) = self.use_valid_autocomplete.as_ref() {
+            if rule.is_enabled() {
+                index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[31]));
+            }
+        }
         index_set
     }
     pub(crate) fn get_disabled_rules(&self) -> FxHashSet<RuleFilter<'static>> {
@@ -3800,31 +3811,36 @@ impl Nursery {
                 index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[25]));
             }
         }
-        if let Some(rule) = self.use_import_restrictions.as_ref() {
+        if let Some(rule) = self.use_explicit_function_return_type.as_ref() {
             if rule.is_disabled() {
                 index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[26]));
             }
         }
-        if let Some(rule) = self.use_sorted_classes.as_ref() {
+        if let Some(rule) = self.use_import_restrictions.as_ref() {
             if rule.is_disabled() {
                 index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[27]));
             }
         }
-        if let Some(rule) = self.use_strict_mode.as_ref() {
+        if let Some(rule) = self.use_sorted_classes.as_ref() {
             if rule.is_disabled() {
                 index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[28]));
             }
         }
-        if let Some(rule) = self.use_trim_start_end.as_ref() {
+        if let Some(rule) = self.use_strict_mode.as_ref() {
             if rule.is_disabled() {
                 index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[29]));
             }
         }
-        if let Some(rule) = self.use_valid_autocomplete.as_ref() {
+        if let Some(rule) = self.use_trim_start_end.as_ref() {
             if rule.is_disabled() {
                 index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[30]));
             }
         }
+        if let Some(rule) = self.use_valid_autocomplete.as_ref() {
+            if rule.is_disabled() {
+                index_set.insert(RuleFilter::Rule(Self::GROUP_NAME, Self::GROUP_RULES[31]));
+            }
+        }
         index_set
     }
     #[doc = r" Checks if, given a rule name, matches one of the rules contained in this category"]
@@ -3965,6 +3981,10 @@ impl Nursery {
                 .use_deprecated_reason
                 .as_ref()
                 .map(|conf| (conf.level(), conf.get_options())),
+            "useExplicitFunctionReturnType" => self
+                .use_explicit_function_return_type
+                .as_ref()
+                .map(|conf| (conf.level(), conf.get_options())),
             "useImportRestrictions" => self
                 .use_import_restrictions
                 .as_ref()

crates/biome_diagnostics_categories/src/categories.rs

@@ -180,6 +180,7 @@ define_categories! {
     "lint/nursery/useConsistentCurlyBraces": "https://biomejs.dev/linter/rules/use-consistent-curly-braces",
     "lint/nursery/useConsistentMemberAccessibility": "https://biomejs.dev/linter/rules/use-consistent-member-accessibility",
     "lint/nursery/useDeprecatedReason": "https://biomejs.dev/linter/rules/use-deprecated-reason",
+    "lint/nursery/useExplicitFunctionReturnType": "https://biomejs.dev/linter/rules/use-explicit-function-return-type",
     "lint/nursery/useImportRestrictions": "https://biomejs.dev/linter/rules/use-import-restrictions",
     "lint/nursery/useJsxCurlyBraceConvention": "https://biomejs.dev/linter/rules/use-jsx-curly-brace-convention",
     "lint/nursery/useSortedClasses": "https://biomejs.dev/linter/rules/use-sorted-classes",

crates/biome_js_analyze/src/lint/nursery.rs

@@ -21,6 +21,7 @@ pub mod use_aria_props_supported_by_role;
 pub mod use_component_export_only_modules;
 pub mod use_consistent_curly_braces;
 pub mod use_consistent_member_accessibility;
+pub mod use_explicit_function_return_type;
 pub mod use_import_restrictions;
 pub mod use_sorted_classes;
 pub mod use_strict_mode;
@@ -50,6 +51,7 @@ declare_lint_group! {
             self :: use_component_export_only_modules :: UseComponentExportOnlyModules ,
             self :: use_consistent_curly_braces :: UseConsistentCurlyBraces ,
             self :: use_consistent_member_accessibility :: UseConsistentMemberAccessibility ,
+            self :: use_explicit_function_return_type :: UseExplicitFunctionReturnType ,
             self :: use_import_restrictions :: UseImportRestrictions ,
             self :: use_sorted_classes :: UseSortedClasses ,
             self :: use_strict_mode :: UseStrictMode ,