[pylint] Detect more exotic NaN literals in PLW0177

Author: robsdedude

crates/ruff_linter/resources/test/fixtures/pylint/nan_comparison.py

@@ -92,3 +92,8 @@
 # OK
 if x == "nan":
     pass
+
+# PLW0117
+# https://github.com/astral-sh/ruff/issues/18596
+assert x == float("-NaN ")
+assert x == float(" \n+nan   \t")

crates/ruff_linter/src/rules/pylint/rules/nan_comparison.rs

@@ -117,12 +117,19 @@ fn is_nan_float(expr: &Expr, semantic: &SemanticModel) -> bool {
         return false;
     };
 
-    if !matches!(
-        value.to_str(),
-        "nan" | "NaN" | "NAN" | "Nan" | "nAn" | "naN" | "nAN" | "NAn"
-    ) {
+    if !is_nan_literal(value.to_str()) {
         return false;
     }
 
     semantic.match_builtin_expr(func, "float")
 }
+
+/// Returns `true` if `value` is a string literal that represents NaN.
+/// E.g., `"NaN"`, `"-nAn"`, `"+nan"`, or even " -NaN "
+fn is_nan_literal(value: &str) -> bool {
+    let mut value = value.trim();
+    if matches!(value.trim().chars().next(), Some('+' | '-')) {
+        value = &value[1..];
+    }
+    value.eq_ignore_ascii_case("nan")
+}

crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLW0177_nan_comparison.py.snap

@@ -107,3 +107,20 @@ nan_comparison.py:60:10: PLW0177 Comparing against a NaN value; use `math.isnan`
 61 |
 62 |     # No errors
    |
+
+nan_comparison.py:98:13: PLW0177 Comparing against a NaN value; use `math.isnan` instead
+   |
+96 | # PLW0117
+97 | # https://github.com/astral-sh/ruff/issues/18596
+98 | assert x == float("-NaN ")
+   |             ^^^^^^^^^^^^^^ PLW0177
+99 | assert x == float(" \n+nan   \t")
+   |
+
+nan_comparison.py:99:13: PLW0177 Comparing against a NaN value; use `math.isnan` instead
+   |
+97 | # https://github.com/astral-sh/ruff/issues/18596
+98 | assert x == float("-NaN ")
+99 | assert x == float(" \n+nan   \t")
+   |             ^^^^^^^^^^^^^^^^^^^^^ PLW0177
+   |