Check for type of array in default

[domharrington]

Prerequisites

• I have read the documentation;
• In the case of a bug report, I understand that providing a SSCCE example is tremendously useful to the maintainers.
• Ideally, I'm providing a sample JSFiddle or a shared playground link demonstrating the issue.

Description

When the default of an array type is null it causes an unrecoverable error:

https://mozilla-services.github.io/react-jsonschema-form/#eyJmb3JtRGF0YSI6e30sInNjaGVtYSI6eyJ0aXRsZSI6IkEgcmVnaXN0cmF0aW9uIGZvcm0iLCJkZXNjcmlwdGlvbiI6IkEgc2ltcGxlIGZvcm0gZXhhbXBsZS4iLCJ0eXBlIjoib2JqZWN0IiwicHJvcGVydGllcyI6eyJhcnJheSI6eyJ0eXBlIjoiYXJyYXkiLCJkZWZhdWx0IjpudWxsLCJpdGVtcyI6eyJ0eXBlIjoic3RyaW5nIn19fX0sInVpU2NoZW1hIjp7fX0=

Steps to Reproduce

1. Go to playground link
2. Check console

Expected behavior

Maybe disregard the default value if !Array.isArray(formData)?
https://github.com/mozilla-services/react-jsonschema-form/blob/cc7e1b4f29ef5d18eb2c595daa186131426e0d49/src/components/fields/ArrayField.js#L296

Actual behavior

Unrecoverable error

Version

Latest on playground.

[essonjon]

And there's a related issue, where a customer did not enter null as the default value but we automatically created it when converting their YAML file to JSON

[ghost]

Is this related to #1238 ?

I'm currently also running into an issue where we define null as default value which causes a render issue.

[domharrington]

I dont think it's related to that, this refers to when an array type has a default value of null which sounds like your issue.

[epicfaace]

This issue might be fixed by #2154 but not sure -- need to check

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Please leave a comment if this is still an issue for you. Thank you.