[wp-trac] [WordPress Trac] #56442: Ensure `wp_editor_set_quality` filter consistently passes output mime type

[WordPress Trac]

#56442: Ensure `wp_editor_set_quality` filter consistently passes output mime type
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 Reporter:  adamsilverstein           |       Owner:  adamsilverstein
     Type:  defect (bug)              |      Status:  assigned
 Priority:  normal                    |   Milestone:  6.1
Component:  Media                     |     Version:  5.8
 Severity:  normal                    |  Resolution:
 Keywords:  has-patch has-unit-tests  |     Focuses:
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Comment (by adamsilverstein):

 [attachment:"56442.diff"]:
 * Add a new test `test_quality_with_image_conversion_file_sizes` to verify
 that the `wp_editor_set_quality` correctly passes the mime type and
 applies correctly:
   - uses the `image_editor_output_format` filter to generate both JPEG and
 WebP sub sizes for a test image (including a `-scaled` version).
   - sets quality very low for JPEG and very high for WebP and verifies
 that the file sizes are all larger for the WebP generated files.
 - Update `WP_Image_Editor::set_quality` to set the output type by calling
 `get_output_format`.

 These tests fail in trunk because the mime type is not set to the output
 type early enough - the first time it is called for WebP (for each editor
 initialization), the mime type was set to JPEG even if the eventual output
 was in WebP. Therefore, certain image sizes were using the JPEG quality
 setting, not the expected WebP quality setting.

 Previous tests for mime type in wp_editor_set_quality weren't catching
 this because they didn't look at all runs of the filter. The new test
 looks at all generated sizes.

 The fix is a [https://github.com/WordPress/wordpress-
 develop/pull/3250/files#diff-
 ade9004b026644e1dcaad2085e43797fd06eb3595c7b5ae0f4c033d046b235c1R264
 single line] change to call `get_output_format` in set_quality. This
 ensures that `$this->output_format` is properly set on the next line and
 the correct mime type is used. After this change, the test passes - the
 correct mime type is passed to the filter..

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Ticket URL: <https://core.trac.wordpress.org/ticket/56442#comment:2>
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