Style/StringLiterals ignores interpolation in multi line strings

[maia]

Rubocop seems to check multi-lined strings one line by the other, and if there's no interpolation in the current line it will report. I do believe that all lines of a multi-line string should use double-quoted strings if there's an interpolation in at least one line:

$ cat test.rb
"This is a multi-line string using interpolation #{Time.now.utc} "\
"but rubocop thinks not all lines should use double quotes."

$ rubocop test.rb --only Style/StringLiterals
Inspecting 1 file
C

Offenses:

test.rb:2:1: C: Prefer single-quoted strings when you don't need string interpolation or special symbols.
"but rubocop thinks not all lines should use double quotes."
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

1 file inspected, 1 offense detected

Is this an incorrect report by rubocop, or is it suggested to mix single and double quotes in multi-line strings?

[alexdowad]

This has already been brought up on this bug tracker before. The RC developers like the current style. If you would like to code up a PR to make this configurable, it will be appreciated.

[maia]

Thanks. I've searched the issues for StringLiterals and didn't find anything related to multi-line strings. Can you point me to the issue? I'd like to read the pro's for the current style, as I didn't even think that mixing quotes in a single string is even allowed:

"This #{Time.now}"\
'feels very wrong'

As for your suggestion, I've just taken a quick look at the code and don't think I could add a configuration option, as it seems as if the checked node is not the entire multi-lined string but each single line is checked one by one. Unfortunately I don't have enough knowledge to alter that behavior.

[alexdowad]

@maia It may have been in the style guide repo.

When you have string literals which are concatenated like this:

"A string" \
'another one'

...they are parsed as a dstr node with one str node under it for each line.

So you could add an on_dstr hook to StringLiterals to make it catch those nodes. Check if all the children are str nodes, and if not, just return. Otherwise, if they are all str, then process them and add offenses as is appropriate.

Then, call ignore_node(node) on each of the str nodes. The on_str hook (which is in StringHelp) already skips nodes which are marked as "ignored", so you can avoid double-processing of the nodes that way.

[maia]

@alexdowad Thanks, I didn't find it in the style guide repo, so maybe the current style is not considered best practice. As for the PR, in case I can find a few spare hours to dig deeper in the internals of rubocop, I will make an attempt, but please don't count on it.

[alexdowad]

I think we can add a config parameter to enforce the use of consistent quote types for multiline-continuation strings. Question: what should the new config parameter be called?

[maia]

How about TreatMultiLinesAsGroup or ConsistentQuotesInMultiLines ?

[jonas054]

ConsistentQuotesInMultilines sounds good. Note that we treat multiline as a single word in configuration, e.g. Style/MultilineMethodCallIndentation.

[alexdowad]

Just pushed a fix for this one to my open PR. The new config parameter is called ConsistentQuotesInMultiline, as suggested.

[maia]

That's great news, thanks a lot!

[maia]

Thanks a lot!