Enable copying text to clipboard for tables with cell_selectable=False

[benedikt-budig]

This PR makes sure that for DataTables with cell_selectable=False, the text content of a cell can be selected and copied to the clipboard as is normally handled by the browser.

It fixes issue #1978; the underlying problem has been open for quite some time (see also plotly/dash-table#822).

Contributor Checklist

• I have run the tests locally and they passed. (refer to testing section in contributing)
• I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR

optionals

• I have added entry in the CHANGELOG.md

[benedikt-budig]

The percy/dash check seems to be failing because the baseline snapshot still has a datepicker that shows June (and not July). Are the baseline snapshots updated automatically after some time?

[alexcjohnson]

@benedikt-budig thanks for the PR! Looks great, and don't worry about Percy, I'll approve those when we're ready.

The one thing we should do is add a test that shows that the bug is fixed. This should be a good starting point (and this test I believe verifies that the normal cell_selectable=True copy still works correctly with your fix?):

dash/components/dash-table/tests/selenium/test_basic_copy_paste.py

Lines 154 to 174 in 565de53

	def test_tbcp004_copy_9_and_10(test):
	test.start_server(get_app())
	source = test.table("table")
	target = test.table("table2")
	source.cell(9, 0).click()
	with test.hold(Keys.SHIFT):
	ActionChains(test.driver).send_keys(Keys.DOWN).perform()
	test.copy()
	target.cell(0, 0).click()
	test.paste()
	for row in range(2):
	for col in range(1):
	assert (
	target.cell(row, col).get_text() == source.cell(row + 9, col).get_text()
	)
	assert test.get_log_errors() == []

[benedikt-budig]

@alexcjohnson thanks a lot for your feedback! In the meantime, I have:

• added a unit test covering the fixed issue, and
• slightly extended Contents to add a new CSS class to table cells indicating whether they are selectable or not.

However, there are now some long_callback tests failing. It seems to me that these tests are operating on the edge of the 10 seconds timeout and I'm not sure if my changes have actually something to do with them failing. Could you help me once again?

[T4rk1n]

However, there are now some long_callback tests failing. It seems to me that these tests are operating on the edge of the 10 seconds timeout and I'm not sure if my changes have actually something to do with them failing. Could you help me once again?

@benedikt-budig There was a lock in the tests for the older implementation of long_callbacks that made the tests flaky, I removed the lock and it should be fine now. You can merge with dev and the tests should pass.

[alexcjohnson]

💃 Beautiful - great call adding the selectable class so we can keep background-color: transparent; in that case. And nice job on the test!

Will merge once tests pass, let's hope merging dev will fix them 🤞

[benedikt-budig]

@alexcjohnson @T4rk1n awesome, thanks for your help and for merging this! 🎉