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Warn when "false" or "true" is the value of a boolean DOM prop #13372

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Merged
gaearon merged 4 commits into from
Aug 14, 2018
Merged

Warn when "false" or "true" is the value of a boolean DOM prop #13372

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1447508
Warn when the string "false" is the value of a boolean DOM prop
motiz88 Aug 11, 2018
b8f83cd
Only warn on exact case match for "false" in DOM boolean props
motiz88 Aug 12, 2018
f3248f2
Warn on string "true" as well as "false" in DOM boolean props
motiz88 Aug 12, 2018
f70a0eb
Clarify warnings on "true" / "false" values in DOM boolean props
motiz88 Aug 12, 2018
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Warn when the string "false" is the value of a boolean DOM prop
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@motiz88
motiz88 committed Aug 11, 2018
commit 1447508e58060942e2224c623b40765b12933e78
26 changes: 26 additions & 0 deletions packages/react-dom/src/__tests__/ReactDOMComponent-test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2506,6 +2506,32 @@ describe('ReactDOMComponent', () => {
});
});

describe('Boolean attributes', function() {
it('warns on the ambiguous string value "false"', function() {
let el;
expect(() => {
el = ReactTestUtils.renderIntoDocument(<div hidden="false" />);
}).toWarnDev(
'Received the string `false` for the boolean attribute `hidden`. ' +
'Did you mean hidden={false}?',
);

expect(el.getAttribute('hidden')).toBe('');
});

it('warns on the ambiguous string value "False"', function() {
let el;
expect(() => {
el = ReactTestUtils.renderIntoDocument(<div hidden="False" />);
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@gaearon gaearon Aug 12, 2018

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Since title case False doesn’t have special meaning I don’t think it’s worth testing for.

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@motiz88 motiz88 Aug 12, 2018

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Happy to take your steer on this, I'd just like to state my case first for completeness: The thing I was trying to make safer was people drawing inferences from one "boolean" HTML attribute to another. Since enumerated attribute values are case-insensitive, spellCheck="False" does behave differently to hidden="False", in exactly the same way as the respective lowercase variants do. I take your point that most people would be using lowercase to begin with, so this is probably a rarer case, but it does theoretically occur.

To clarify, you're referring to dropping the toLowerCase() in the actual check, as well as removing this test, right?

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@gaearon gaearon Aug 12, 2018

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Yeah. I see your point but I think it's unlikely enough to be written accidentally and we want to make the checks as cheap as possible. Strict comparison is better than extra toLowerCase call.

}).toWarnDev(
'Received the string `False` for the boolean attribute `hidden`. ' +
'Did you mean hidden={false}?',
);

expect(el.getAttribute('hidden')).toBe('');
});
});

describe('Hyphenated SVG elements', function() {
it('the font-face element is not a custom element', function() {
let el;
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20 changes: 20 additions & 0 deletions packages/react-dom/src/shared/ReactDOMUnknownPropertyHook.js
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@ import warning from 'shared/warning';

import {
ATTRIBUTE_NAME_CHAR,
BOOLEAN,
RESERVED,
shouldRemoveAttributeWithWarning,
getPropertyInfo,
Expand Down Expand Up @@ -226,6 +227,25 @@ if (__DEV__) {
return false;
}

// Warn when passing the string 'false' into a boolean prop
if (
propertyInfo !== null &&
propertyInfo.type === BOOLEAN &&
typeof value === 'string' &&
value.toLowerCase() === 'false'
) {
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@gaearon gaearon Aug 12, 2018

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Let’s make value === 'false' the first condition. Since it’s rare we won’t have to check most other conditions.

warning(
false,
'Received the string `%s` for the boolean attribute `%s`. ' +
'Did you mean %s={false}?',
value,
name,
name,
);
warnedProperties[name] = true;
return true;
}

return true;
};
}
Expand Down