Include newline in one-line raw string literal?

Question

Constructing a string for bulk posting for the purposes of Elasticsearch, I need to conform to a particular newline formatting. A raw string literal like this does the job:

    let json = format!(r#"{{"index":{{"_id":"{}"}}}}
{}
"#, *num, self.ldoc_texts[sequence_type]);
    self.bulk_post_str.push_str(&json);

Lines 2 and 3 above are deliberately written with no indent in order not to introduce spurious spaces at the start of the line.

Is there any way to write this on the same line?

let json = format!(r#"{{"index":{{"_id":"{}"}}}}\n{}\n"#, *num, self.ldoc_texts[sequence_type]);
self.bulk_post_str.push_str(&json);

The above doesn't work: the literal sequence "\n" is found in the resulting string, instead of newlines.

Refer to [Rust by example: Strings](https://doc.rust-lang.org/rust-by-example/std/str.html): raw string literals don’t support escapes, so you can use a normal string literal and escape the required characters (newlines, double quotes, etc.) or stick with the multiline raw string literal. If this addresses your question, I can write it as an answer. If not, what did I miss? — jsejcksn, Aug 31 '23 at 08:06

score 2 · Accepted Answer · edited Aug 31 '23 at 08:16

2

You can use concat! to stick raw and regular literals together.

print!(concat!(r#"This is a "raw" literal"#, "\n", r#"continued after "#, "\n"))

edited Aug 31 '23 at 08:16

cafce25

15,907
4
25
31

answered Aug 31 '23 at 08:04

n. m. could be an AI

112,515
14
128
243

Thanks. This doesn't seem to be all that practical when I need to include interpolated variables. Will update question. – mike rodent Aug 31 '23 at 08:23
1

@mikerodent You need to do it the other way around: `format!(concat!(...))` – n. m. could be an AI Aug 31 '23 at 08:27

score 1 · Answer 2 · answered Aug 31 '23 at 09:39

The options mentioned so far do not seem very readable. I'd go for something that shows the intent more clearly, e.g.

use serde_json::{json, to_string}, std::fmt::Write;

let json = json!({"index": {"_id": *num}});
writeln!(self.bulk_post_str, "{}", to_string(&json).unwrap()).unwrap();
writeln!(self.bulk_post_str, "{}", self.ldoc_texts[sequence_type]).unwrap();

This is a bit more verbose, but I think it's a lot easier to read.

The unwrap()s are a bit unfortunate, but they are all for infallible calls.

Include newline in one-line raw string literal?

2 Answers2