docs(documents): add section on setting deeply nested properties, including warning about nullish coalescing assignment #14972
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
…luding warning about nullish coalescing assignment Fix #14944
hasezoey
approved these changes
Oct 17, 2024
| // The following does **NOT** work. | ||
| // Do not use the following pattern with Mongoose documents. | ||
| const doc4 = new TestModel(); | ||
| (doc4.nested.subdoc ??= {}).name = 'Charlie Smith'; |
There was a problem hiding this comment.
does this not work because mongoose is cloning on assignment? (i have tried in a node REPL)
ret = (doc4.nested.subdoc ??= {})
ret === doc4.nested.subdoc // eval "false"There was a problem hiding this comment.
Yes. The problem is the following:
const x = {};
(doc4.nested.subdoc ??= x) === x; // true
doc4.nested.subdoc === x; // falseBasically a.b ??= x evaluates to x, not the value of a.b after the assignment. Which isn't a big deal in most cases, but with Mongoose the distinction matters.
We need to clone because doc4.nested.subdoc needs change tracking. This may be a case where using proxies instead of Object.defineProperty() for change tracking would help.
hasezoey
added
the
docs
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Fix #14944
Summary
Add section in the docs about setting deeply nested paths. Clarify that
?.and??are fine, we also support.get()and.set(), but??=comes with caveats.Examples