The view mode source misses a requirements check for CCK

OK then reworded for the current problem and demoting.

I think this is still an issue, as I just ran into it. Here's what I did:

1. Started with a brand-new D6 site, only the "standard" install. CCK ("Content" module) not enabled, confirmed that "content_node_field_instance" table doesn't exist in the database.
2. Added 2 nodes to the D6 site (one "story", one "page").
3. Ran the migration using this manifest: https://drupal.org/comment/8615887#comment-8615887
4. Received the following error:

~/Sites/imp $  drush migrate-manifest mysql://imp@localhost/drupal6 manifest.yml
Migration failed with source plugin exception: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'drupal6.content_node_field_instance' doesn't exist: SELECT            [error]
cnfi.display_settings AS display_settings
FROM 
{content_node_field_instance} cnfi; Array
(
)

Migration d6_cck_field_revision:page did not meet the requirements                                                                                                              [error]
Migration d6_cck_field_revision:story did not meet the requirements                                                                                                             [error]
Migration d6_field did not meet the requirements                                                                                                                                [error]
Migration d6_field_instance did not meet the requirements                                                                                                                       [error]
Migration d6_field_instance_widget_settings did not meet the requirements                                                                                                       [error]
Migration d6_cck_field_values:page did not meet the requirements                                                                                                                [error]
Migration d6_cck_field_values:story did not meet the requirements                                                                                                               [error]
~/Sites/imp $  

I then enabled CCK ("Content" module only), and re-ran the migration - both nodes imported properly, with the following output:

~/Sites/imp $  drush migrate-manifest mysql://imp@localhost/drupal6 manifest.yml
Migration d6_field_instance did not meet the requirements                                                                                                                       [error]
Migration d6_field_instance_widget_settings did not meet the requirements                                                                                                       [error]
~/Sites/imp $  

-mike

Added a checkRequirements() to the ViewModeBase source class.

I also fixed up two tiny coding standard errors in the tests that use that source class while I was testing :)

OK, turns out we shouldn't be using checkRequirements() anymore but source_provider. I've updated the two child classes to use source_provider and also fixed up UploadInstance which was still using checkRequirements().

arghhh

Very nice bugfix bouquet.

Re-rolled.

Finally the bot agrees with me :)

Committed and pushed to 8.x. Thanks!