fix(linter/unicorn/prefer-spread): stop checking string split calls (#26935)

Stop reporting and fixing `String#split('')`, matching Unicorn's removal of this check in v66. Splitting into UTF-16 code units and spreading into code points can produce different results, for example for `"🦄"`.

Fixes #26873

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

@@ -5,7 +5,7 @@ use oxc_ast::{
 };
 use oxc_diagnostics::OxcDiagnostic;
 use oxc_macros::declare_oxc_lint;
-use oxc_span::{GetSpan, Span};
+use oxc_span::Span;
 
 use crate::{AstNode, ast_util, context::LintContext, rule::Rule};
 
@@ -169,39 +169,6 @@ fn check_unicorn_prefer_spread<'a>(
                 member_expr.object(),
             );
         }
-        // `string.split()`
-        "split" => {
-            if call_expr.arguments.len() != 1 {
-                return;
-            }
-
-            let Some(expr) = call_expr.arguments[0].as_expression() else {
-                return;
-            };
-            let Expression::StringLiteral(string_lit) = expr.without_parentheses() else {
-                return;
-            };
-
-            if !string_lit.value.is_empty() {
-                return;
-            }
-
-            ctx.diagnostic_with_fix(
-                unicorn_prefer_spread_diagnostic(call_expr.span, "string.split()"),
-                |fixer| {
-                    let needs_semi = ast_util::could_be_asi_hazard(node, ctx);
-                    let callee_obj = member_expr.object().without_parentheses();
-                    let prefix = if needs_semi { ";" } else { "" };
-                    fixer.replace(
-                        call_expr.span,
-                        format!(
-                            "{prefix}[...{}]",
-                            callee_obj.span().source_text(ctx.source_text())
-                        ),
-                    )
-                },
-            );
-        }
         _ => {}
     }
 }
@@ -436,7 +403,23 @@ fn test() {
         r#""".split(string)"#,
         "string.split()",
         r#"string.notSplit("")"#,
-        // r#"const notString = 0; notString.split("")"#,
+        r#"const notString = 0; notString.split("")"#,
+        r#""string".split("")"#,
+        r#""string".split('')"#,
+        r#"unknown.split("")"#,
+        r#"const characters = "string".split("")"#,
+        r#"(( (( (( "string" )).split ))( (("")) ) ))"#,
+        r#"bar()
+            foo.split("")"#,
+        r#"unknown.split("")"#,
+        r#""🦄".split("")"#,
+        r#"const {length} = "🦄".split("")"#,
+        r#""foo bar baz".split("")"#,
+        "foo()\nstr.split(\"\")",
+        r#"'string'
+str.split("")"#,
+        r#""string"
+str.split("")"#,
     ];
 
     let fail = vec![
@@ -598,16 +581,6 @@ fn test() {
             foo.toSpliced()",
         r#""".toSpliced()"#,
         "new Uint8Array([10, 20, 30, 40, 50]).toSpliced()",
-        r#""string".split("")"#,
-        r#""string".split('')"#,
-        r#"unknown.split("")"#,
-        r#"const characters = "string".split("")"#,
-        r#"(( (( (( "string" )).split ))( (("")) ) ))"#,
-        r#"bar()
-            foo.split("")"#,
-        r#"unknown.split("")"#,
-        r#""🦄".split("")"#,
-        r#"const {length} = "🦄".split("")"#,
     ];
 
     let fix = vec![
@@ -644,11 +617,6 @@ fn test() {
         ("const copy = array.toSpliced()", "const copy = [...array]"),
         // `array.toSpliced()` - ASI hazard cases
         ("foo()\narray.toSpliced()", "foo()\n;[...array]"),
-        // `string.split()`
-        (r#""🦄".split("")"#, r#"[..."🦄"]"#),
-        (r#""foo bar baz".split("")"#, r#"[..."foo bar baz"]"#),
-        // `string.split()` - ASI hazard cases
-        ("foo()\nstr.split(\"\")", "foo()\n;[...str]"),
         (
             r"Array.from(path.matchAll(/\{([^{}?]+\??)\}/g))",
             "[...path.matchAll(/\\{([^{}?]+\\??)\\}/g)]",
@@ -680,17 +648,6 @@ fn test() {
         ("for (array.slice();;) {}", "for ([...array];;) {}"),
         ("switch (array.slice()[0]) {}", "switch ([...array][0]) {}"),
         ("`template`\narray.toSpliced()", "`template`\n;[...array]"),
-        (
-            r#"'string'
-str.split("")"#,
-            "'string'\n;[...str]",
-        ),
-        (
-            r#""string"
-str.split("")"#,
-            r#""string"
-;[...str]"#,
-        ),
         (
             "foo()\nArray.from(set).map(x => x).filter(Boolean).length",
             "foo()\n;[...set].map(x => x).filter(Boolean).length",

crates/oxc_linter/src/snapshots/unicorn_prefer_spread.snap

@@ -915,67 +915,3 @@ source: crates/oxc_linter/src/tester.rs
    · ────────────────────────────────────────────────
    ╰────
   help: The spread operator (`...`) is more concise and readable.
-
-  ⚠ unicorn(prefer-spread): Prefer the spread operator (`...`) over string.split()
-   ╭─[prefer_spread.tsx:1:1]
- 1 │ "string".split("")
-   · ──────────────────
-   ╰────
-  help: The spread operator (`...`) is more concise and readable.
-
-  ⚠ unicorn(prefer-spread): Prefer the spread operator (`...`) over string.split()
-   ╭─[prefer_spread.tsx:1:1]
- 1 │ "string".split('')
-   · ──────────────────
-   ╰────
-  help: The spread operator (`...`) is more concise and readable.
-
-  ⚠ unicorn(prefer-spread): Prefer the spread operator (`...`) over string.split()
-   ╭─[prefer_spread.tsx:1:1]
- 1 │ unknown.split("")
-   · ─────────────────
-   ╰────
-  help: The spread operator (`...`) is more concise and readable.
-
-  ⚠ unicorn(prefer-spread): Prefer the spread operator (`...`) over string.split()
-   ╭─[prefer_spread.tsx:1:20]
- 1 │ const characters = "string".split("")
-   ·                    ──────────────────
-   ╰────
-  help: The spread operator (`...`) is more concise and readable.
-
-  ⚠ unicorn(prefer-spread): Prefer the spread operator (`...`) over string.split()
-   ╭─[prefer_spread.tsx:1:4]
- 1 │ (( (( (( "string" )).split ))( (("")) ) ))
-   ·    ────────────────────────────────────
-   ╰────
-  help: The spread operator (`...`) is more concise and readable.
-
-  ⚠ unicorn(prefer-spread): Prefer the spread operator (`...`) over string.split()
-   ╭─[prefer_spread.tsx:2:13]
- 1 │ bar()
- 2 │             foo.split("")
-   ·             ─────────────
-   ╰────
-  help: The spread operator (`...`) is more concise and readable.
-
-  ⚠ unicorn(prefer-spread): Prefer the spread operator (`...`) over string.split()
-   ╭─[prefer_spread.tsx:1:1]
- 1 │ unknown.split("")
-   · ─────────────────
-   ╰────
-  help: The spread operator (`...`) is more concise and readable.
-
-  ⚠ unicorn(prefer-spread): Prefer the spread operator (`...`) over string.split()
-   ╭─[prefer_spread.tsx:1:1]
- 1 │ "🦄".split("")
-   · ──────────────
-   ╰────
-  help: The spread operator (`...`) is more concise and readable.
-
-  ⚠ unicorn(prefer-spread): Prefer the spread operator (`...`) over string.split()
-   ╭─[prefer_spread.tsx:1:18]
- 1 │ const {length} = "🦄".split("")
-   ·                  ──────────────
-   ╰────
-  help: The spread operator (`...`) is more concise and readable.