Formatted strings

[tmssngr]

I use formatted strings very often, but sometimes forget to write the leading f. Unfortunately, the compiler does not catch it. Do others have similar problems, e.g. with other programming languages?

What do you think - which is used more often: formatted strings or strings containing {? I would think about whether formatted strings should be the default and if there shouldn't be a formatting, one should either escape the { or rather use a raw string.

[ivov]

Other than flipping the default, the simplest here might be a check that warns you if the name in braces in a regular string resolves to a variable in scope, similar to Ruff's lint rule.

Edit: Addressed at #1208

[tmssngr]

Then you need to be able to mark a string as don't-warn-me-because-it-is-intentional.

Why there is string interpolation at all? To make building chained strings as easy as possible. IMHO it boils down to the question: which is used more often: formatted strings or strings containing {?

[ivov]

Indeed, you can #[allow()] the new lint or use a raw string r"..." if no escapes are needed. The lint exemption is paid only by strings that contain a brace and match an in-scope name. Flipping the f-string default means every brace-containing string would have to be marked whether or not anything matches, and raw strings cannot contain a " so e.g. a JSON payload would have to double every brace instead. Doubling is also lossy: {{.Name}} becomes {.Name} in Go templates.

[tmssngr]

If JSON or other strings containing " is a relatively common case, maybe a string literal should be created/modified to support that. In Java, for example, a multi-line string (text block) starts with """ and can contain " or "" - but this is a different topic.

[tmssngr]

Another formatted string related question: is it possible to specify how, e.g., a number is displayed? I often need it as 2 or 4 digit hex number.