wp_get_attachment_image should use wp_get_attachment_metadata

[JorritSchippers]

wp_get_attachment_image uses get_post_meta( $attachment_id, '_wp_attachment_metadata', true ) to fetch attachment meta data, even though the function wp_get_attachment_metadata does exactly this. This means that the filter wp_get_attachment_metadata can't be used.

The function wp_get_attachment_image calls both wp_calculate_image_srcset and wp_calculate_image_sizes with the image meta data. These two functions specify that their inputs come from wp_get_attachment_metadata, but this is not the case in practise.

BTW: media.php contains more situations where get_post_meta( $attachment_id, '_wp_attachment_metadata', true ) could be replaced by wp_get_attachment_metadata($attachment_id).

[JorritSchippers]

patch with test

[JorritSchippers]

fix for previous patch

[wonderboymusic]

In 38296:

Media: use wp_get_attachment_metadata() instead of get_post_meta() where appropriate.

Adds unit test.

Props JorritSchippers.
Fixes #36246.

[pento]

The unit tests for this are failing.

1) Tests_Media::test_wp_get_attachment_image_should_use_wp_get_attachment_metadata
Failed asserting that two strings are identical.
--- Expected
+++ Actual
@@ @@
-<img width="999" height="999" src="http://example.org/wp-content/uploads/2016/03/test-image-testsize-999x999.png" class="attachment-testsize size-testsize" alt="test-image-large.png" srcset="http://example.org/wp-content/uploads/2016/03/test-image-large-150x150.png 150w, http://example.org/wp-content/uploads/2016/03/test-image-testsize-999x999.png 999w" sizes="(max-width: 999px) 100vw, 999px" />
+<img width="999" height="999" src="http://example.org/wp-content/uploads/2016/08/test-image-testsize-999x999.png" class="attachment-testsize size-testsize" alt="test-image-large.png" srcset="http://example.org/wp-content/uploads/2016/08/test-image-testsize-999x999.png 999w, http://example.org/wp-content/uploads/2016/08/test-image-large-150x150.png 150w" sizes="(max-width: 709px) 85vw, (max-width: 909px) 67vw, (max-width: 1362px) 62vw, 840px" />

[wonderboymusic]

In 38302:

Media: fix unit test after [38296].

​https://en.wikipedia.org/wiki/Coupling_(computer_programming)#Disadvantages

Fixes #36246.

[johnbillion]

In 38760:

Media: Correct the hostname used in the wp_get_attachment_metadata() test.

See #36246

[johnbillion]

Sort-of followup: #38264