fix false positive in suspicious_open_options, make paths work

tests/ui/open_options.rs

@@ -1,6 +1,18 @@
+#![allow(unused_must_use)]
+#![warn(clippy::nonsensical_open_options)]
+
 use std::fs::OpenOptions;
-#[allow(unused_must_use)]
-#[warn(clippy::nonsensical_open_options)]
+
+trait OpenOptionsExt {
+    fn truncate_write(&mut self, opt: bool) -> &mut Self;
+}
+
+impl OpenOptionsExt for OpenOptions {
+    fn truncate_write(&mut self, opt: bool) -> &mut Self {
+        self.truncate(opt).write(opt)
+    }
+}
+
 fn main() {
     OpenOptions::new().read(true).truncate(true).open("foo.txt");
     //~^ ERROR: file opened with `truncate` and `read`
@@ -29,6 +41,12 @@ fn main() {
     let mut options = std::fs::OpenOptions::new();
     options.read(true);
     options.read(false);
-    //#~^ ERROR: the method `read` is called more than once
+    // Possible future improvement: recognize open options method call chains across statements.
     options.open("foo.txt");
+
+    let mut options = std::fs::OpenOptions::new();
+    options.truncate(true);
+    options.create(true).open("foo.txt");
+
+    OpenOptions::new().create(true).truncate_write(true).open("foo.txt");
 }

tests/ui/open_options.stderr

@@ -1,5 +1,5 @@
 error: file opened with `truncate` and `read`
-  --> $DIR/open_options.rs:5:5
+  --> $DIR/open_options.rs:17:5
    |
 LL |     OpenOptions::new().read(true).truncate(true).open("foo.txt");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -8,43 +8,43 @@ LL |     OpenOptions::new().read(true).truncate(true).open("foo.txt");
    = help: to override `-D warnings` add `#[allow(clippy::nonsensical_open_options)]`
 
 error: file opened with `append` and `truncate`
-  --> $DIR/open_options.rs:8:5
+  --> $DIR/open_options.rs:20:5
    |
 LL |     OpenOptions::new().append(true).truncate(true).open("foo.txt");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: the method `read` is called more than once
-  --> $DIR/open_options.rs:11:35
+  --> $DIR/open_options.rs:23:35
    |
 LL |     OpenOptions::new().read(true).read(false).open("foo.txt");
    |                                   ^^^^^^^^^^^
 
 error: the method `create` is called more than once
-  --> $DIR/open_options.rs:16:10
+  --> $DIR/open_options.rs:28:10
    |
 LL |         .create(false)
    |          ^^^^^^^^^^^^^
 
 error: the method `write` is called more than once
-  --> $DIR/open_options.rs:19:36
+  --> $DIR/open_options.rs:31:36
    |
 LL |     OpenOptions::new().write(true).write(false).open("foo.txt");
    |                                    ^^^^^^^^^^^^
 
 error: the method `append` is called more than once
-  --> $DIR/open_options.rs:21:37
+  --> $DIR/open_options.rs:33:37
    |
 LL |     OpenOptions::new().append(true).append(false).open("foo.txt");
    |                                     ^^^^^^^^^^^^^
 
 error: the method `truncate` is called more than once
-  --> $DIR/open_options.rs:23:39
+  --> $DIR/open_options.rs:35:39
    |
 LL |     OpenOptions::new().truncate(true).truncate(false).open("foo.txt");
    |                                       ^^^^^^^^^^^^^^^
 
 error: the method `read` is called more than once
-  --> $DIR/open_options.rs:26:41
+  --> $DIR/open_options.rs:38:41
    |
 LL |     std::fs::File::options().read(true).read(false).open("foo.txt");
    |                                         ^^^^^^^^^^^

tests/ui/open_options_fixable.stderr

@@ -4,7 +4,9 @@ error: file opened with `create`, but `truncate` behavior not defined
 LL |     OpenOptions::new().create(true).open("foo.txt");
    |                        ^^^^^^^^^^^^- help: add: `.truncate(true)`
    |
-   = help: if you intend to overwrite an existing file entirely, call `.truncate(true)`. if you instead know that you may want to keep some parts of the old file, call `.truncate(false)`. Alternatively, use `.append` to append to the file instead of overwriting it.
+   = help: if you intend to overwrite an existing file entirely, call `.truncate(true)`
+   = help: if you instead know that you may want to keep some parts of the old file, call `.truncate(false)`
+   = help: alternatively, use `.append(true)` to append to the file instead of overwriting it
    = note: `-D clippy::suspicious-open-options` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::suspicious_open_options)]`