NamedNodeMap/getNamedItem is not defined to be potentially "null" #17695
Description
TypeScript Version: 2.4.2
I've recently faced in issue accessing the NamedNodeMap of a Node - a user managed to insert an img tag without a src attribute. My code accessed attributes.getNamedItem("src") on the node, and (accidentially) did not check if the resulting attr exists before accessing its .value, and the function crashed with a type error.
While not performing this check is my personal mistake, I've figured out that getNamedItem is not defined to possibly return null: https://github.com/Microsoft/TypeScript/blob/master/lib/lib.es6.d.ts#L14075
However, this function will return null in case the attributes does not exist:
https://developer.mozilla.org/en-US/docs/Web/API/NamedNodeMap/getNamedItem
This should hold true for getNamedItemNS as well.
Thus, as I've strict resp. strictNullChecks enabled in in my tsconfig.json, the compiler should raise in error when not checking the result for null (see code below).
Code
const node: Node = // ... an <img> node
const src: Attr = this.attributes.getNamedItem("src"); // should complain that src should be of type Attr | null
const valueLength = src.value.length; // should complain that src might be null.Expected behavior:
The code mentioned above compiles without an error that src might be null, even with the config strict resp. strictNullChecks enabled. It does because the definition mentions that the result of getNamedItem is always an Attr.
Actual behavior:
The code mentioned above should raise a compiler error in case strict resp. strictNullChecks is enabled. The definition should mention that the result of getNamedItem is of type Attr | null.