[refurb] Implement read-whole-file [FURB101]

crates/ruff_linter/resources/test/fixtures/refurb/FURB101.py

@@ -0,0 +1,105 @@
+def foo():
+    ...
+
+
+def bar(x):
+    ...
+
+
+# Errors.
+
+# FURB101
+with open("file.txt") as f:
+    x = f.read()
+
+# FURB101
+with open("file.txt", "rb") as f:
+    x = f.read()
+
+# FURB101
+with open("file.txt", mode="rb") as f:
+    x = f.read()
+
+# FURB101
+with open("file.txt", encoding="utf8") as f:
+    x = f.read()
+
+# FURB101
+with open("file.txt", errors="ignore") as f:
+    x = f.read()
+
+# FURB101
+with open("file.txt", errors="ignore", mode="rb") as f:
+    x = f.read()
+
+# FURB101
+with open("file.txt", mode="r") as f:  # noqa: FURB120
+    x = f.read()
+
+# FURB101
+with open(foo(), "rb") as f:
+    # The body of `with` is non-trivial, but the recommendation holds.
+    bar("pre")
+    bar(f.read())
+    bar("post")
+    print("Done")
+
+# FURB101
+with open("a.txt") as a, open("b.txt", "rb") as b:
+    x = a.read()
+    y = b.read()
+
+# FURB101
+with foo() as a, open("file.txt") as b, foo() as c:
+    # We have other things in here, multiple with items, but
+    # the user reads the whole file and that bit they can replace.
+    bar(a)
+    bar(bar(a + b.read()))
+    bar(c)
+
+
+# Non-errors.
+
+f2 = open("file2.txt")
+with open("file.txt") as f:
+    x = f2.read()
+
+with open("file.txt") as f:
+    # Path.read_text() does not support size, so ignore this
+    x = f.read(100)
+
+# mode is dynamic
+with open("file.txt", foo()) as f:
+    x = f.read()
+
+# keyword mode is incorrect
+with open("file.txt", mode="a+") as f:
+    x = f.read()
+
+# enables line buffering, not supported in read_text()
+with open("file.txt", buffering=1) as f:
+    x = f.read()
+
+# force CRLF, not supported in read_text()
+with open("file.txt", newline="\r\n") as f:
+    x = f.read()
+
+# dont mistake "newline" for "mode"
+with open("file.txt", newline="b") as f:
+    x = f.read()
+
+# I guess we can possibly also report this case, but the question
+# is why the user would put "r+" here in the first place.
+with open("file.txt", "r+") as f:
+    x = f.read()
+
+# Even though we read the whole file, we do other things.
+with open("file.txt") as f:
+    x = f.read()
+    f.seek(0)
+    x += f.read(100)
+
+open = bar
+# Not a real `open`.
+with open("file.txt") as f:
+    x = f.read()

crates/ruff_linter/src/checkers/ast/analyze/statement.rs

@@ -1166,6 +1166,9 @@ pub(crate) fn statement(stmt: &Stmt, checker: &mut Checker) {
             if checker.enabled(Rule::RedefinedLoopName) {
                 pylint::rules::redefined_loop_name(checker, stmt);
             }
+            if checker.enabled(Rule::ReadWholeFile) {
+                refurb::rules::read_whole_file(checker, with_stmt);
+            }
         }
         Stmt::While(ast::StmtWhile { body, orelse, .. }) => {
             if checker.enabled(Rule::FunctionUsesLoopVariable) {

crates/ruff_linter/src/codes.rs

@@ -914,6 +914,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Flake8Slots, "002") => (RuleGroup::Unspecified, rules::flake8_slots::rules::NoSlotsInNamedtupleSubclass),
 
         // refurb
+        (Refurb, "101") => (RuleGroup::Preview, rules::refurb::rules::ReadWholeFile),
         (Refurb, "105") => (RuleGroup::Preview, rules::refurb::rules::PrintEmptyString),
         #[allow(deprecated)]
         (Refurb, "113") => (RuleGroup::Nursery, rules::refurb::rules::RepeatedAppend),

crates/ruff_linter/src/rules/refurb/mod.rs

@@ -14,6 +14,7 @@ mod tests {
     use crate::test::test_path;
     use crate::{assert_messages, settings};
 
+    #[test_case(Rule::ReadWholeFile, Path::new("FURB101.py"))]
     #[test_case(Rule::RepeatedAppend, Path::new("FURB113.py"))]
     #[test_case(Rule::DeleteFullSlice, Path::new("FURB131.py"))]
     #[test_case(Rule::CheckAndRemoveFromSet, Path::new("FURB132.py"))]

crates/ruff_linter/src/rules/refurb/rules/mod.rs

@@ -1,6 +1,7 @@
 pub(crate) use check_and_remove_from_set::*;
 pub(crate) use delete_full_slice::*;
 pub(crate) use print_empty_string::*;
+pub(crate) use read_whole_file::*;
 pub(crate) use reimplemented_starmap::*;
 pub(crate) use repeated_append::*;
 pub(crate) use slice_copy::*;
@@ -9,6 +10,7 @@ pub(crate) use unnecessary_enumerate::*;
 mod check_and_remove_from_set;
 mod delete_full_slice;
 mod print_empty_string;
+mod read_whole_file;
 mod reimplemented_starmap;
 mod repeated_append;
 mod slice_copy;