LibJS: Add new host hook, specify template literals and more #14904
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davidot
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linusg
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Aug 17, 2022
This hook allows us to reject private elements on certain exotic objects like the window object in browser. Note that per the spec we should only call this hook if the host is a web browser, however because LibJS has no way of knowing whether it is in a web browser environment we just always call the host hook.
Assuming we had at least one argument meant that the ...arg count would underflow causing the bound function to have length 0 instead of the given length when binding with no arguments.
We use strtod to convert a string to number after checking whether the string is [+-]Infinity, however strtod also checks for either 'inf' or 'infinity' in a case-insensitive. There are still valid cases for strtod to return infinity like 10e100000 so we just check if the "number" contains 'i' or 'I' in which case the strtod infinity is not valid.
Since tagged template literals can inspect the raw string it is not a syntax error to have invalid escapes. However the cooked value should be `undefined`. We accomplish this by tracking whether parse_string_literal fails and then using a NullLiteral (since UndefinedLiteral is not a thing) and finally converting null in tagged template execution to undefined.
We cache on the AST node side as this is easier to track a position, we just have to take care to wrap the values in a handle to make sure they are not garbage collected.
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I have not implemented the hook in browser yet as the PR is not merged yet:
whatwg/html#8198
I do have a patch ready but it might be more complicated by extending location and or window
The original JS PR has already been merged:
tc39/ecma262#2807