Validation error raised when validating post with Schema.org script added by All In One SEO

[westonruter]

Bug Description

Originally reported in the support forum. When the All in One SEO Pack plugin is active and you view a single post, you'll see that there is no validation error in the admin bar. However, once you click to Validate then you'll see a validation error reported:

The problem is that source stack comments are erroneously getting injected into the script.

Expected Behaviour

Comments should be stripped from JSON scripts when validating.

Steps to reproduce

1. Activate AIOSEO plugin.
2. Enable Standard mode or Transitional mode in the AMP plugin.
3. View a single post in AMP.
4. Notice no validation error appears in the admin bar.
5. Click the validate link, and now see a validation error reported.

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Acceptance criteria

Implementation brief

QA testing instructions

Demo

Changelog entry

[westonruter]

Here is a temporary workaround mini plugin: https://gist.github.com/westonruter/5d66967fe586fb64d7244d3ad0dc89cb

[westonruter]

Given that <!-- appearing anywhere in JSON is also a validation error, the fix here could be also to encode such hyphens as escape sequences. This would prevent issues like #3935 from occurring. Nevertheless, comments as a whole should also be removed to account for source stack comments being injected during validation.