Fix option focus bug caused by IE11 option value workaround.

[sznurek]

Whenever children of an element are changed Preact resets the value to an empty string. This is a hack for an IE11 bug triggered whenever option value field is inferred from the text inside the element.

This hack breaks the behaviour of <select> element on other browsers: if you click on the dropdown, mouse over another option (but don't click) and rendering happens at this moment, the focus will go back to the current element. This is caused by setting the value attribute on elements even though it isn't necessary (the value didn't change since the last time but Preact forces it to be set anyway).

To resolve the issue, we save the value dom attribute before we place children and then check if it has changed afterwards, as a way to detect whether we need to activate the hack.

I'm not sure that this is the best solution to the problem - please let me know if you have a better one in mind!

Here's a link for reproducing the issue (at least on Firefox 86.0.1 on Windows 10). To reproduce, click on the dropdown, hover on any element other than the first one, wait for the callback to fire - you should see the focus moving to the first element.

[github-actions[bot]]

📊 Tachometer Benchmark Results

Summary

duration

• 02_replace1k: unsure 🔍 -2% - +0% (-4.29ms - +0.78ms)
  ^{preact-local vs preact-master}
• 03_update10th1k_x16: unsure 🔍 -5% - +4% (-1.91ms - +1.59ms)
  ^{preact-local vs preact-master}
• 07_create10k: unsure 🔍 -1% - +1% (-11.37ms - +25.91ms)
  ^{preact-local vs preact-master}
• filter_list: unsure 🔍 -2% - +2% (-0.67ms - +0.68ms)
  ^{preact-local vs preact-master}
• hydrate1k: unsure 🔍 -2% - +0% (-3.54ms - +0.48ms)
  ^{preact-local vs preact-master}
• many_updates: unsure 🔍 -7% - +3% (-2.97ms - +1.49ms)
  ^{preact-local vs preact-master}
• text_update: unsure 🔍 -5% - +2% (-0.14ms - +0.06ms)
  ^{preact-local vs preact-master}

usedJSHeapSize

• 02_replace1k: unsure 🔍 +0% - +0% (+0.00ms - +0.01ms)
  ^{preact-local vs preact-master}
• 03_update10th1k_x16: unsure 🔍 -0% - +0% (-0.01ms - +0.01ms)
  ^{preact-local vs preact-master}
• 07_create10k: unsure 🔍 -0% - +0% (-0.00ms - +0.00ms)
  ^{preact-local vs preact-master}
• filter_list: unsure 🔍 -0% - +0% (-0.00ms - +0.00ms)
  ^{preact-local vs preact-master}
• hydrate1k: unsure 🔍 -0% - +1% (-0.01ms - +0.04ms)
  ^{preact-local vs preact-master}
• many_updates: unsure 🔍 +0% - +0% (+0.00ms - +0.00ms)
  ^{preact-local vs preact-master}
• text_update: unsure 🔍 +0% - +0% (+0.00ms - +0.00ms)
  ^{preact-local vs preact-master}

Results

02_replace1k

• Browser: chrome-headless 89.0.4389.90
• Sample size: 80
• Built by: Benchmarks #161

• Commit: 512bbfd

duration

Version	Avg time	vs preact-master	vs preact-local
preact-master	174.10ms - 178.05ms	-	unsure 🔍 -0% - +2% -0.78ms - +4.29ms
preact-local	172.73ms - 175.92ms	unsure 🔍 -2% - +0% -4.29ms - +0.78ms	-

usedJSHeapSize

Version	Avg time	vs preact-master	vs preact-local
preact-master	3.57ms - 3.57ms	-	unsure 🔍 -0% - -0% -0.01ms - -0.00ms
preact-local	3.57ms - 3.58ms	unsure 🔍 +0% - +0% +0.00ms - +0.01ms	-

run-warmup-0

Version	Avg time	vs preact-master	vs preact-local
preact-master	65.66ms - 66.80ms	-	unsure 🔍 -1% - +1% -0.96ms - +0.66ms
preact-local	65.81ms - 66.96ms	unsure 🔍 -1% - +1% -0.66ms - +0.96ms	-

run-warmup-1

Version	Avg time	vs preact-master	vs preact-local
preact-master	102.04ms - 103.78ms	-	unsure 🔍 -1% - +1% -1.12ms - +1.30ms
preact-local	101.98ms - 103.66ms	unsure 🔍 -1% - +1% -1.30ms - +1.12ms	-

run-warmup-2

Version	Avg time	vs preact-master	vs preact-local
preact-master	103.87ms - 112.40ms	-	faster ✔ 1% - 10% 0.49ms - 11.31ms
preact-local	110.70ms - 117.37ms	slower ❌ 0% - 11% 0.49ms - 11.31ms	-

run-warmup-3

Version	Avg time	vs preact-master	vs preact-local
preact-master	67.86ms - 74.49ms	-	unsure 🔍 -3% - +9% -1.69ms - +6.46ms
preact-local	66.43ms - 71.15ms	unsure 🔍 -9% - +2% -6.46ms - +1.69ms	-

run-warmup-4

Version	Avg time	vs preact-master	vs preact-local
preact-master	107.00ms - 113.36ms	-	unsure 🔍 -5% - +3% -5.40ms - +3.65ms
preact-local	107.84ms - 114.27ms	unsure 🔍 -3% - +5% -3.65ms - +5.40ms	-

run-final

Version	Avg time	vs preact-master	vs preact-local
preact-master	64.78ms - 67.56ms	-	slower ❌ 1% - 6% 0.42ms - 3.81ms
preact-local	63.08ms - 65.02ms	faster ✔ 1% - 6% 0.42ms - 3.81ms	-

03_update10th1k_x16

• Browser: chrome-headless 89.0.4389.90
• Sample size: 60
• Built by: Benchmarks #161

• Commit: 512bbfd

duration

Version	Avg time	vs preact-master	vs preact-local
preact-master	39.39ms - 41.83ms	-	unsure 🔍 -4% - +5% -1.59ms - +1.91ms
preact-local	39.19ms - 41.71ms	unsure 🔍 -5% - +4% -1.91ms - +1.59ms	-

usedJSHeapSize

Version	Avg time	vs preact-master	vs preact-local
preact-master	3.65ms - 3.66ms	-	unsure 🔍 -0% - +0% -0.01ms - +0.01ms
preact-local	3.65ms - 3.66ms	unsure 🔍 -0% - +0% -0.01ms - +0.01ms	-

07_create10k

• Browser: chrome-headless 89.0.4389.90
• Sample size: 50
• Built by: Benchmarks #161

• Commit: 512bbfd

duration

Version	Avg time	vs preact-master	vs preact-local
preact-master	1828.95ms - 1851.86ms	-	unsure 🔍 -1% - +1% -25.91ms - +11.37ms
preact-local	1832.98ms - 1862.37ms	unsure 🔍 -1% - +1% -11.37ms - +25.91ms	-

usedJSHeapSize

Version	Avg time	vs preact-master	vs preact-local
preact-master	25.97ms - 25.97ms	-	unsure 🔍 -0% - +0% -0.00ms - +0.00ms
preact-local	25.97ms - 25.97ms	unsure 🔍 -0% - +0% -0.00ms - +0.00ms	-

filter_list

• Browser: chrome-headless 89.0.4389.90
• Sample size: 50
• Built by: Benchmarks #161

• Commit: 512bbfd

duration

Version	Avg time	vs preact-master	vs preact-local
preact-master	28.88ms - 29.90ms	-	unsure 🔍 -2% - +2% -0.68ms - +0.67ms
preact-local	28.96ms - 29.83ms	unsure 🔍 -2% - +2% -0.67ms - +0.68ms	-

usedJSHeapSize

Version	Avg time	vs preact-master	vs preact-local
preact-master	1.58ms - 1.59ms	-	unsure 🔍 -0% - +0% -0.00ms - +0.00ms
preact-local	1.58ms - 1.59ms	unsure 🔍 -0% - +0% -0.00ms - +0.00ms	-

hydrate1k

• Browser: chrome-headless 89.0.4389.90
• Sample size: 50
• Built by: Benchmarks #161

• Commit: 512bbfd

duration

Version	Avg time	vs preact-master	vs preact-local
preact-master	183.35ms - 186.44ms	-	unsure 🔍 -0% - +2% -0.48ms - +3.54ms
preact-local	182.07ms - 184.65ms	unsure 🔍 -2% - +0% -3.54ms - +0.48ms	-

usedJSHeapSize

Version	Avg time	vs preact-master	vs preact-local
preact-master	6.17ms - 6.19ms	-	unsure 🔍 -1% - +0% -0.04ms - +0.01ms
preact-local	6.17ms - 6.21ms	unsure 🔍 -0% - +1% -0.01ms - +0.04ms	-

many_updates

• Browser: chrome-headless 89.0.4389.90
• Sample size: 70
• Built by: Benchmarks #161

• Commit: 512bbfd

duration

Version	Avg time	vs preact-master	vs preact-local
preact-master	41.15ms - 44.37ms	-	unsure 🔍 -4% - +7% -1.49ms - +2.97ms
preact-local	40.48ms - 43.56ms	unsure 🔍 -7% - +3% -2.97ms - +1.49ms	-

usedJSHeapSize

Version	Avg time	vs preact-master	vs preact-local
preact-master	4.83ms - 4.83ms	-	unsure 🔍 -0% - -0% -0.00ms - -0.00ms
preact-local	4.83ms - 4.83ms	unsure 🔍 +0% - +0% +0.00ms - +0.00ms	-

text_update

• Browser: chrome-headless 89.0.4389.90
• Sample size: 100
• Built by: Benchmarks #161

• Commit: 512bbfd

duration

Version	Avg time	vs preact-master	vs preact-local
preact-master	2.91ms - 3.05ms	-	unsure 🔍 -2% - +5% -0.06ms - +0.14ms
preact-local	2.87ms - 3.01ms	unsure 🔍 -5% - +2% -0.14ms - +0.06ms	-

usedJSHeapSize

Version	Avg time	vs preact-master	vs preact-local
preact-master	0.98ms - 0.98ms	-	unsure 🔍 -0% - -0% -0.00ms - -0.00ms
preact-local	0.98ms - 0.98ms	unsure 🔍 +0% - +0% +0.00ms - +0.00ms	-

_{tachometer-reporter-action v2 for Benchmarks}

[coveralls]

Coverage remained the same at 99.445% when pulling 512bbfd5a540ec302027b1b5727505d9309d9a2f on sznurek:master into c7f57db13af43b8cc3353a138639ad9dd9523e16 on preactjs:master.

[sznurek]

Is there anything else I should do before this pull request is reviewed?