Fix quoted-strings checks in flow maps and sequences

[robherring]

Flow maps and sequences need quotes if the values contain any of the flow tokens ({}, [], ','). However, yamllint generates false positives in these cases:

$ yamllint -d 'rules: {quoted-strings: {required: only-when-needed}}' - <<<'field: ["string[bracket]"]' 1:9 error string value is redundantly quoted with any quotes (quoted-strings)

To fix this, track when inside a flow map/sequence and skip the quoting checks except for the quoting type.

Closes #516

[coveralls]

coverage: 99.399% (+0.002%) from 99.397% when pulling a962b4101ade797eaae75d746f31f3463278181d on robherring:flow-quote-fix into ca7f8b972cbbc6058e8d532e82a05d34a9897cd7 on adrienverge:master.

[robherring]

Hello and thanks for tackling this!

It looks good at first glance, but could you add more tests with nested flows, to prove the functionnality of flow_cnt? (By the way you can rename it to flow_count or flow_nest_count for clarity)

Sure.

Does this address the field: ["foo,bar"] case too?

Yes

From what I see in the new test cases it reports [foo, "foo,bar"] as a failure, which is wrong, isn't it? 🤔

That one is testing the quotes are the right type.