[pyupgrade] Prevent infinite loop with I002 and UP026 (#20327)

## Summary

Fixes #19842

Prevent infinite loop with I002 and UP026

- Implement isort-aware handling for UP026 (deprecated mock import):
- Add CLI integration tests in crates/ruff/tests/lint.rs:

## Test Plan

I have added two integration tests
`pyupgrade_up026_respects_isort_required_import_fix` and
`pyupgrade_up026_respects_isort_required_import_from_fix` in
`crates/ruff/tests/lint.rs`.

Author: TaKO8Ki

crates/ruff/tests/lint.rs

@@ -5059,6 +5059,59 @@ fn flake8_import_convention_unused_aliased_import_no_conflict() {
     );
 }
 
+// https://github.com/astral-sh/ruff/issues/19842
+#[test]
+fn pyupgrade_up026_respects_isort_required_import_fix() {
+    assert_cmd_snapshot!(
+        Command::new(get_cargo_bin(BIN_NAME))
+            .arg("--isolated")
+            .arg("check")
+            .arg("-")
+            .args(["--select", "I002,UP026"])
+            .arg("--config")
+            .arg(r#"lint.isort.required-imports=["import mock"]"#)
+            .arg("--fix")
+            .arg("--no-cache")
+            .pass_stdin("1\n"),
+        @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    import mock
+    1
+
+    ----- stderr -----
+    Found 1 error (1 fixed, 0 remaining).
+    "
+    );
+}
+
+// https://github.com/astral-sh/ruff/issues/19842
+#[test]
+fn pyupgrade_up026_respects_isort_required_import_from_fix() {
+    assert_cmd_snapshot!(
+        Command::new(get_cargo_bin(BIN_NAME))
+            .arg("--isolated")
+            .arg("check")
+            .arg("-")
+            .args(["--select", "I002,UP026"])
+            .arg("--config")
+            .arg(r#"lint.isort.required-imports = ["from mock import mock"]"#)
+            .arg("--fix")
+            .arg("--no-cache")
+            .pass_stdin("from mock import mock\n"),
+        @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    from mock import mock
+
+    ----- stderr -----
+    All checks passed!
+    "
+    );
+}
+
 // See: https://github.com/astral-sh/ruff/issues/16177
 #[test]
 fn flake8_pyi_redundant_none_literal() {

crates/ruff_linter/src/rules/pyupgrade/rules/deprecated_mock_import.rs

@@ -17,6 +17,7 @@ use crate::Locator;
 use crate::checkers::ast::Checker;
 use crate::cst::matchers::{match_import, match_import_from, match_statement};
 use crate::fix::codemods::CodegenStylist;
+use crate::rules::pyupgrade::rules::is_import_required_by_isort;
 use crate::{AlwaysFixableViolation, Edit, Fix};
 
 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
@@ -299,7 +300,13 @@ pub(crate) fn deprecated_mock_import(checker: &Checker, stmt: &Stmt) {
 
                 // Add a `Diagnostic` for each `mock` import.
                 for name in names {
-                    if &name.name == "mock" || &name.name == "mock.mock" {
+                    if (&name.name == "mock" || &name.name == "mock.mock")
+                        && !is_import_required_by_isort(
+                            &checker.settings().isort.required_imports,
+                            stmt.into(),
+                            name,
+                        )
+                    {
                         let mut diagnostic = checker.report_diagnostic(
                             DeprecatedMockImport {
                                 reference_type: MockReference::Import,
@@ -319,13 +326,25 @@ pub(crate) fn deprecated_mock_import(checker: &Checker, stmt: &Stmt) {
         Stmt::ImportFrom(ast::StmtImportFrom {
             module: Some(module),
             level,
+            names,
             ..
         }) => {
             if *level > 0 {
                 return;
             }
 
             if module == "mock" {
+                if names.iter().any(|alias| {
+                    alias.name.as_str() == "mock"
+                        && is_import_required_by_isort(
+                            &checker.settings().isort.required_imports,
+                            stmt.into(),
+                            alias,
+                        )
+                }) {
+                    return;
+                }
+
                 let mut diagnostic = checker.report_diagnostic(
                     DeprecatedMockImport {
                         reference_type: MockReference::Import,