feat(rome_analyze): noSparseArray

crates/rome_analyze/src/analyzers/no_sparse_array.rs

@@ -0,0 +1,83 @@
+use rome_console::markup;
+use rome_diagnostics::Applicability;
+use rome_js_factory::make;
+use rome_js_syntax::{
+    JsAnyArrayElement, JsAnyExpression, JsAnyRoot, JsArrayExpression, TriviaPieceKind,
+};
+use rome_rowan::{AstNode, AstNodeExt, AstSeparatedList};
+
+use crate::registry::{JsRuleAction, Rule, RuleDiagnostic};
+use crate::{ActionCategory, RuleCategory};
+
+pub(crate) enum NoSparseArray {}
+
+impl Rule for NoSparseArray {
+    const NAME: &'static str = "noSparseArray";
+    const CATEGORY: RuleCategory = RuleCategory::Lint;
+
+    type Query = JsArrayExpression;
+    type State = ();
+
+    fn run(node: &Self::Query) -> Option<Self::State> {
+        // We defer collect `JsHole` index until user want to apply code action.
+        node.elements().iter().find_map(|element| {
+            if matches!(element.ok()?, JsAnyArrayElement::JsArrayHole(_),) {
+                Some(())
+            } else {
+                None
+            }
+        })
+    }
+
+    fn diagnostic(node: &Self::Query, _state: &Self::State) -> Option<RuleDiagnostic> {
+        Some(RuleDiagnostic::warning(
+            node.syntax().text_trimmed_range(),
+markup! {
+                "This "<Emphasis>"array"</Emphasis>" contains an "<Emphasis>"empty slot"</Emphasis>"."
+            }
+            .to_owned()
+        ))
+    }
+
+    fn action(root: JsAnyRoot, node: &Self::Query, _state: &Self::State) -> Option<JsRuleAction> {
+        let mut final_array_element_list = node.elements();
+
+        for (i, item) in final_array_element_list.iter().enumerate() {
+            if matches!(item, Ok(JsAnyArrayElement::JsArrayHole(_))) {
+                let undefine_indent = if i == 0 {
+                    make::ident("undefined")
+                } else {
+                    make::ident("undefined")
+                        .with_leading_trivia(std::iter::once((TriviaPieceKind::Whitespace, " ")))
+                };
+                let ident_expr =
+                    make::js_identifier_expression(make::js_reference_identifier(undefine_indent));
+                // Why we need to use `final_array_element_list.iter().nth(i)` instead of `item`, because every time we
+                // call `replace_node` the previous iteration `item` is not the descent child of current `final_array_element_list` any more.
+                let n_element = final_array_element_list.iter().nth(i)?.ok()?;
+                final_array_element_list = final_array_element_list.replace_node(
+                    n_element,
+                    JsAnyArrayElement::JsAnyExpression(JsAnyExpression::JsIdentifierExpression(
+                        ident_expr,
+                    )),
+                )?;
+            }
+        }
+
+        let root = root.replace_node(
+            node.clone(),
+            make::js_array_expression(
+                node.l_brack_token().ok()?,
+                final_array_element_list,
+                node.r_brack_token().ok()?,
+            ),
+        )?;
+
+        Some(JsRuleAction {
+            category: ActionCategory::QuickFix,
+            applicability: Applicability::MaybeIncorrect,
+            message: markup! { "Replace hole with undefined" }.to_owned(),
+            root,
+        })
+    }
+}

crates/rome_analyze/src/registry.rs

@@ -43,6 +43,7 @@ impl_registry_builders!(
     NoDelete,
     NoDoubleEquals,
     NoNegationElse,
+    NoSparseArray,
     UseSingleCaseStatement,
     UseSingleVarDeclarator,
     UseValidTypeof,

crates/rome_analyze/tests/specs/noSparseArray.js

@@ -0,0 +1,10 @@
+// valid
+const a = [ 1, 2, ];
+
+// invalid
+const b = [/**test*/,];
+const c = [,,];
+const d = [,2];
+
+const e = [1,,]
+const f = [1,,2]

crates/rome_analyze/tests/specs/noSparseArray.js.snap

@@ -0,0 +1,122 @@
+---
+source: crates/rome_analyze/tests/spec_tests.rs
+assertion_line: 98
+expression: noSparseArray.js
+---
+# Input
+```js
+// valid
+const a = [ 1, 2, ];
+
+// invalid
+const b = [/**test*/,];
+const c = [,,];
+const d = [,2];
+
+const e = [1,,]
+const f = [1,,2]
+
+```
+
+# Diagnostics
+```
+warning[noSparseArray]: This array contains an empty slot.
+  ┌─ noSparseArray.js:5:11
+  │
+5 │ const b = [/**test*/,];
+  │           ------------
+
+Suggested fix: Replace hole with undefined
+    | @@ -2,7 +2,7 @@
+1 1 |   const a = [ 1, 2, ];
+2 2 |   
+3 3 |   // invalid
+4   | - const b = [/**test*/,];
+  4 | + const b = [/**test*/undefined,];
+5 5 |   const c = [,,];
+6 6 |   const d = [,2];
+7 7 |   
+
+
+```
+
+```
+warning[noSparseArray]: This array contains an empty slot.
+  ┌─ noSparseArray.js:6:11
+  │
+6 │ const c = [,,];
+  │           ----
+
+Suggested fix: Replace hole with undefined
+    | @@ -3,7 +3,7 @@
+2 2 |   
+3 3 |   // invalid
+4 4 |   const b = [/**test*/,];
+5   | - const c = [,,];
+  5 | + const c = [undefined, undefined,];
+6 6 |   const d = [,2];
+7 7 |   
+8 8 |   const e = [1,,]
+
+
+```
+
+```
+warning[noSparseArray]: This array contains an empty slot.
+  ┌─ noSparseArray.js:7:11
+  │
+7 │ const d = [,2];
+  │           ----
+
+Suggested fix: Replace hole with undefined
+    | @@ -4,7 +4,7 @@
+3 3 |   // invalid
+4 4 |   const b = [/**test*/,];
+5 5 |   const c = [,,];
+6   | - const d = [,2];
+  6 | + const d = [undefined,2];
+7 7 |   
+8 8 |   const e = [1,,]
+9 9 |   const f = [1,,2]
+
+
+```
+
+```
+warning[noSparseArray]: This array contains an empty slot.
+  ┌─ noSparseArray.js:9:11
+  │
+9 │ const e = [1,,]
+  │           -----
+
+Suggested fix: Replace hole with undefined
+    | @@ -6,5 +6,5 @@
+5 5 |   const c = [,,];
+6 6 |   const d = [,2];
+7 7 |   
+8   | - const e = [1,,]
+  8 | + const e = [1, undefined,]
+9 9 |   const f = [1,,2]
+
+
+```
+
+```
+warning[noSparseArray]: This array contains an empty slot.
+   ┌─ noSparseArray.js:10:11
+   │
+10 │ const f = [1,,2]
+   │           ------
+
+Suggested fix: Replace hole with undefined
+      | @@ -7,4 +7,4 @@
+ 6  6 |   const d = [,2];
+ 7  7 |   
+ 8  8 |   const e = [1,,]
+ 9    | - const f = [1,,2]
+    9 | + const f = [1, undefined,2]
+
+
+```
+
+