Single quotes are sometimes replaced with double quotes even when "prettier.singleQuote: true" is specified

[alexjlockwood]

I am using the vscode extension and am having an issue with the prettier.singleQuote setting. The only settings I have customized are:

"prettier.singleQuote": true,
"prettier.trailingComma": "all",
"prettier.printWidth": 100

Specifically, when prettier is run on a string like this:

'You\'ll lose any unsaved changes.'

the string is changed to:

"You'll lose any unsaved changes."

The expected behavior (I think) is to continue using single quotes since the setting prohibits the use of double quotes.

My temporary workaround is to change the string to:

`You'll lose any unsaved changes.`

[josephfrazier]

This is as intended. From https://github.com/prettier/prettier/tree/21733e441dc01f7d85b483edee92b7e7507bfd9a#quotes:

• If the number of quotes outweighs the other quote, the quote which is less used will be used to format the string - Example: "I'm double quoted" results in "I'm double quoted" and "This \"example\" is single quoted" results in 'This "example" is single quoted'.

Maybe we should change the preceding description "Use single quotes instead of double quotes." to something like "Prefer single quotes over double quotes.".

[lydell]

FYI, this is how Prettier handles quotes:

1. JSX always uses double quotes.
2. The quote that results in the least number of escapes is chosen.
3. Finally, the singleQuote option is used to choose quote.

See also #973.

[alexjlockwood]

The reason I reported is because prettier modifies the code to use double quotes, which results in an eslint error. Is there any way this can be avoided?

[lydell]

Yes! Disable the ESLint rule. It gains you nothing.

[alexjlockwood]

Ahh, good point! Thanks for the advice and the great tool. :)

[oliamb]

Instead of disabling it entirely, you can use avoidEscape option (http://eslint.org/docs/rules/quotes).

[lydell]

@oliamb Even if you do, the rule still doesn't gain you anything, does it? It only makes ESLint take a little longer to run?

[oliamb]

I have at least one interesting use case that can justify this rule. When using string constants, it is useful to be able to search and replace using 'myStringConstant' rather than myStringConstant or /['"]myStringConstant['"]/. I was wondering if the rule in prettier will forbad me to do so anymore but it is not the case as it is still deterministic ('it is green' VS "it's green")

NB: let's maybe not dive into whether it is a good idea to use string constants ;-)

[brocoli]

Code style is all about consistency, it doesn't need to "gain something" beyond consistency for it to be useful.

Still, using avoidEscape in eslint seems like a good idea, and the correct resolution to this issue anyway.

[neossoftware]

My .prettierrc looks :

{ "useTabs": false, "printWidth": 80, "tabWidth": 2, "singleQuote": true, "trailingComma": "none", "jsxBracketSameLine": false, "parser": "typescript" }

and it works perfect, I had the problem that I wanted to format my typescript clases but when I was using Prettier it always changed the single quote to double, I only modify the parser to Typescript.

[ConnorChristie]

FYI the tslint rule for avoid escape is here:
https://github.com/palantir/tslint/blob/46098f7b7f0f63f8d04b63e9a3598d1fc467b35f/test/rules/quotemark/double-avoid-escape/tslint.json