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{print,write}-with-newline: do not suggest empty format string #6042

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Sep 16, 2020
Merged

{print,write}-with-newline: do not suggest empty format string #6042

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6 changes: 5 additions & 1 deletion clippy_lints/src/write.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -322,11 +322,15 @@ impl EarlyLintPass for Write {
}

/// Given a format string that ends in a newline and its span, calculates the span of the
/// newline.
/// newline, or the format string itself if the format string consists solely of a newline.
fn newline_span(fmtstr: &StrLit) -> Span {
let sp = fmtstr.span;
let contents = &fmtstr.symbol.as_str();

if *contents == r"\n" {
return sp;
}

let newline_sp_hi = sp.hi()
- match fmtstr.style {
StrStyle::Cooked => BytePos(1),
Expand Down
1 change: 1 addition & 0 deletions tests/ui/print_with_newline.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ fn main() {
print!("Hello {}\n", "world");
print!("Hello {} {}\n", "world", "#2");
print!("{}\n", 1265);
print!("\n");

// these are all fine
print!("");
Expand Down
23 changes: 17 additions & 6 deletions tests/ui/print_with_newline.stderr
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Expand Up @@ -44,7 +44,18 @@ LL | println!("{}", 1265);
| ^^^^^^^ --

error: using `print!()` with a format string that ends in a single newline
--> $DIR/print_with_newline.rs:30:5
--> $DIR/print_with_newline.rs:12:5
|
LL | print!("/n");
| ^^^^^^^^^^^^
|
help: use `println!` instead
|
LL | println!();
| ^^^^^^^ --

error: using `print!()` with a format string that ends in a single newline
--> $DIR/print_with_newline.rs:31:5
|
LL | print!("//n"); // should fail
| ^^^^^^^^^^^^^^
Expand All @@ -55,7 +66,7 @@ LL | println!("/"); // should fail
| ^^^^^^^ --

error: using `print!()` with a format string that ends in a single newline
--> $DIR/print_with_newline.rs:37:5
--> $DIR/print_with_newline.rs:38:5
|
LL | / print!(
LL | | "
Expand All @@ -70,7 +81,7 @@ LL | ""
|

error: using `print!()` with a format string that ends in a single newline
--> $DIR/print_with_newline.rs:41:5
--> $DIR/print_with_newline.rs:42:5
|
LL | / print!(
LL | | r"
Expand All @@ -85,7 +96,7 @@ LL | r""
|

error: using `print!()` with a format string that ends in a single newline
--> $DIR/print_with_newline.rs:49:5
--> $DIR/print_with_newline.rs:50:5
|
LL | print!("/r/n"); //~ ERROR
| ^^^^^^^^^^^^^^^
Expand All @@ -96,7 +107,7 @@ LL | println!("/r"); //~ ERROR
| ^^^^^^^ --

error: using `print!()` with a format string that ends in a single newline
--> $DIR/print_with_newline.rs:50:5
--> $DIR/print_with_newline.rs:51:5
|
LL | print!("foo/rbar/n") // ~ ERROR
| ^^^^^^^^^^^^^^^^^^^^
Expand All @@ -106,5 +117,5 @@ help: use `println!` instead
LL | println!("foo/rbar") // ~ ERROR
| ^^^^^^^ --

error: aborting due to 9 previous errors
error: aborting due to 10 previous errors

1 change: 1 addition & 0 deletions tests/ui/write_with_newline.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ fn main() {
write!(&mut v, "Hello {}\n", "world");
write!(&mut v, "Hello {} {}\n", "world", "#2");
write!(&mut v, "{}\n", 1265);
write!(&mut v, "\n");

// These should be fine
write!(&mut v, "");
Expand Down
23 changes: 17 additions & 6 deletions tests/ui/write_with_newline.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,18 @@ LL | writeln!(&mut v, "{}", 1265);
| ^^^^^^^ --

error: using `write!()` with a format string that ends in a single newline
--> $DIR/write_with_newline.rs:35:5
--> $DIR/write_with_newline.rs:17:5
|
LL | write!(&mut v, "/n");
| ^^^^^^^^^^^^^^^^^^^^
|
help: use `writeln!()` instead
|
LL | writeln!(&mut v, );
| ^^^^^^^ --

error: using `write!()` with a format string that ends in a single newline
--> $DIR/write_with_newline.rs:36:5
|
LL | write!(&mut v, "//n"); // should fail
| ^^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -55,7 +66,7 @@ LL | writeln!(&mut v, "/"); // should fail
| ^^^^^^^ --

error: using `write!()` with a format string that ends in a single newline
--> $DIR/write_with_newline.rs:42:5
--> $DIR/write_with_newline.rs:43:5
|
LL | / write!(
LL | | &mut v,
Expand All @@ -72,7 +83,7 @@ LL | ""
|

error: using `write!()` with a format string that ends in a single newline
--> $DIR/write_with_newline.rs:47:5
--> $DIR/write_with_newline.rs:48:5
|
LL | / write!(
LL | | &mut v,
Expand All @@ -89,7 +100,7 @@ LL | r""
|

error: using `write!()` with a format string that ends in a single newline
--> $DIR/write_with_newline.rs:56:5
--> $DIR/write_with_newline.rs:57:5
|
LL | write!(&mut v, "/r/n"); //~ ERROR
| ^^^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -100,7 +111,7 @@ LL | writeln!(&mut v, "/r"); //~ ERROR
| ^^^^^^^ --

error: using `write!()` with a format string that ends in a single newline
--> $DIR/write_with_newline.rs:57:5
--> $DIR/write_with_newline.rs:58:5
|
LL | write!(&mut v, "foo/rbar/n");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -110,5 +121,5 @@ help: use `writeln!()` instead
LL | writeln!(&mut v, "foo/rbar");
| ^^^^^^^ --

error: aborting due to 9 previous errors
error: aborting due to 10 previous errors