[pylint] Detect indirect pathlib.Path usages for unspecified-encoding (PLW1514) (#19304)

## Summary

Fixes #19294

---------

Co-authored-by: Brent Westbrook <[email protected]>

Author: danparizher

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

@@ -91,9 +91,16 @@ def func(*args, **kwargs):
 Path("foo.txt").write_text(text, *args)
 Path("foo.txt").write_text(text, **kwargs)
 
-# Violation but not detectable
+# https://github.com/astral-sh/ruff/issues/19294
 x = Path("foo.txt")
 x.open()
 
 # https://github.com/astral-sh/ruff/issues/18107
 codecs.open("plw1514.py", "r", "utf-8").close() # this is fine
+
+# function argument annotated as Path
+from pathlib import Path
+
+def format_file(file: Path):
+    with file.open() as f:
+        contents = f.read()

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

@@ -4,6 +4,7 @@ use ruff_macros::{ViolationMetadata, derive_message_formats};
 use ruff_python_ast::name::QualifiedName;
 use ruff_python_ast::{self as ast, Expr};
 use ruff_python_semantic::SemanticModel;
+use ruff_python_semantic::analyze::typing;
 use ruff_text_size::{Ranged, TextRange};
 
 use crate::checkers::ast::Checker;
@@ -111,20 +112,34 @@ enum Callee<'a> {
 }
 
 impl<'a> Callee<'a> {
+    fn is_pathlib_path_call(expr: &Expr, semantic: &SemanticModel) -> bool {
+        if let Expr::Call(ast::ExprCall { func, .. }) = expr {
+            semantic
+                .resolve_qualified_name(func)
+                .is_some_and(|qualified_name| {
+                    matches!(qualified_name.segments(), ["pathlib", "Path"])
+                })
+        } else {
+            false
+        }
+    }
+
     fn try_from_call_expression(
         call: &'a ast::ExprCall,
         semantic: &'a SemanticModel,
     ) -> Option<Self> {
         if let Expr::Attribute(ast::ExprAttribute { attr, value, .. }) = call.func.as_ref() {
-            // Check for `pathlib.Path(...).open(...)` or equivalent
-            if let Expr::Call(ast::ExprCall { func, .. }) = value.as_ref() {
-                if semantic
-                    .resolve_qualified_name(func)
-                    .is_some_and(|qualified_name| {
-                        matches!(qualified_name.segments(), ["pathlib", "Path"])
-                    })
-                {
-                    return Some(Callee::Pathlib(attr));
+            // Direct: Path(...).open()
+            if Self::is_pathlib_path_call(value, semantic) {
+                return Some(Callee::Pathlib(attr));
+            }
+            // Indirect: x.open() where x = Path(...)
+            else if let Expr::Name(name) = value.as_ref() {
+                if let Some(binding_id) = semantic.only_binding(name) {
+                    let binding = semantic.binding(binding_id);
+                    if typing::is_pathlib_path(binding, semantic) {
+                        return Some(Callee::Pathlib(attr));
+                    }
                 }
             }
         }

crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLW1514_unspecified_encoding.py.snap

@@ -435,3 +435,41 @@ unspecified_encoding.py:80:1: PLW1514 [*] `pathlib.Path(...).write_text` without
 81 81 | 
 82 82 | # Non-errors.
 83 83 | Path("foo.txt").open(encoding="utf-8")
+
+unspecified_encoding.py:96:1: PLW1514 [*] `pathlib.Path(...).open` in text mode without explicit `encoding` argument
+   |
+94 | # https://github.com/astral-sh/ruff/issues/19294
+95 | x = Path("foo.txt")
+96 | x.open()
+   | ^^^^^^ PLW1514
+97 |
+98 | # https://github.com/astral-sh/ruff/issues/18107
+   |
+   = help: Add explicit `encoding` argument
+
+ℹ Unsafe fix
+93 93 | 
+94 94 | # https://github.com/astral-sh/ruff/issues/19294
+95 95 | x = Path("foo.txt")
+96    |-x.open()
+   96 |+x.open(encoding="utf-8")
+97 97 | 
+98 98 | # https://github.com/astral-sh/ruff/issues/18107
+99 99 | codecs.open("plw1514.py", "r", "utf-8").close() # this is fine
+
+unspecified_encoding.py:105:10: PLW1514 [*] `pathlib.Path(...).open` in text mode without explicit `encoding` argument
+    |
+104 | def format_file(file: Path):
+105 |     with file.open() as f:
+    |          ^^^^^^^^^ PLW1514
+106 |         contents = f.read()
+    |
+    = help: Add explicit `encoding` argument
+
+ℹ Unsafe fix
+102 102 | from pathlib import Path
+103 103 | 
+104 104 | def format_file(file: Path):
+105     |-    with file.open() as f:
+    105 |+    with file.open(encoding="utf-8") as f:
+106 106 |         contents = f.read()