Entity actions fail when clicking at the start of an entity with icon

[thibaudcolas]

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It seems like the initial cause itself is a part of the prefixing icon and not being able to select the first letter when visible (the w in Toms screen). At that point the cursor will jump to the beginning of the icon which does not hold the link but still shows the dialog.

When you disable the icon this is partially the same behaviour except the 1st letter is now clickable / targetable. But also when the cursor is in front of the first letter, it shows the dialog, but does not respond to either Edit or Remove.

Update: DraftJS Link demo shows the same behaviour with cursor in front of the text.

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Initially reported at springload/wagtaildraftail#47 by @tomdyson, with further testing by @jjanssen.

[thibaudcolas]

It looks like the code searching for the existing entity fails when the selection is collapsed right at the start the entity text.

[thibaudcolas]

This is likely to be the same underlying issue as #87. Although visually shown as being "on" the entity, and although the editing UI opens as if the entity editing UI was active, the selection is actually outside of the entity.