How do I break a string in YAML over multiple lines?

I have a very long string:

Key: 'this is my very very very very very very long string'

I would like to express it over multiple shorter lines, e.g.,

Key: 'this is my very very very ' +
     'long string'

I would like to use quotes as above, so that I don't need to escape anything within the string.

Solution

Using yaml folded style. The indention in each line will be ignored. A line break will be inserted at the end.

Key: >
  This is a very long sentence
  that spans several lines in the YAML
  but which will be rendered as a string
  with only a single carriage return appended to the end.

http://symfony.com/doc/current/components/yaml/yaml_format.html

You can use the "block chomping indicator" to eliminate the trailing line break, as follows:

Key: >-
  This is a very long sentence
  that spans several lines in the YAML
  but which will be rendered as a string
  with NO carriage returns.

In either case, each line break is replaced by a space.

There are other control tools available as well (for controlling indentation for example).

See https://yaml-multiline.info/