Comments (7)
I think we also had a change to eval (I think indirect eval) to enable jits to do certain kinds of work⦠do you know why the change to wasn't recorded? i don't know the details. It is the case that I think of when I think of breaking changes and I would love to have it written down for the future.
the list as it is does not seem very useful. It would take some work to make it useful and I think this is worthwhile to do. I'd like to have something that records breaking changes and why we did them. This will help us make decisions, especially if we have a classification of types of breaking changes. I agree, it isn't very useful to list every error that has been used up for adding new functionality: this can be covered with more broad language that i would be happy to help with. We are just so used to doing it and it can be confusing when viewed from the outside (I have spoken to people who were confused by this). Namely, you can't run a program that uses new syntax on an older browser, it is not backwards compatible. In the same vein, we can broadly cover a class of changes to prototype properties, as mentioned by @bakkot.
It also looks like this can be cleaned up to use more consistent language (i can make a PR)
from ecma262.
Annex F doesn't document all observable changes. It's always a judgement call whether a given change is worth documenting. IMO this one probably isn't, though I'm open to hearing arguments (e.g. if any in-the-wild programs broke).
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Yeah it's likely not something that will impact most (or any) program. The missing test and lack of pick up by an implementation however is more worry some. Looks like test262 cases were updated for the change, but a test262 issue was open later to indicate coverage was not sufficient, but that seems to have fallen through the cracks.
from ecma262.
Observable changes are sufficiently rare that I think the default should be to document them, with exclusion requiring specific justification.
from ecma262.
The 262 editors discussed this, and we're not clear on the purpose or the utility of Annex F as it stands. We plan to bring this to committee to gather more input from other delegates to see if they find it useful.
Our personal opinion is roughly that it might not be useful enough to warrant keeping and keep maintaining.
- We don't know what the intended audience or purposes of Annex F is. Who's reading it, and what are they wanting to find out? Is it more of a historical curiosity?
- It would be difficult to keep it complete. What kind of changes make the cut for "backwards breaking" and what don't? For example, existing entries like "it is no longer an early error to have duplicate property names in Object Initializers." don't seem like it should be included. We shouldn't be calling out new features as backwards breaking.
from ecma262.
Also, in reality it turns out that adding new properties to Array.prototype causes real-life breakages more often than most of the stuff listed here, but I have a hard time imagining that listing every new prototype property as a breaking change is worth doing.
from ecma262.
Making something that errors no longer error isn't breaking; intentionally making a change that could break existing code is.
While it's a fair point that new globals and prototype methods could qualify, I would assume these don't "count". What's left is what I would assume Annex F contains.
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Related Issues (20)
- RegExp `\p`: `Unknown` value for `Script` / `Script_Extension` HOT 1
- `RevalidateAtomicAccess` will incorrectly fail on valid indices HOT 1
- 'instance of the Object type' should be 'member of the Object type' in Section 6.1.7 HOT 1
- Synthesized constructor in ClassDefinitionEvaluation is missing [[PrivateMethods]] and [[Fields]] HOT 1
- questions (possible bugs) re specification/language identity HOT 2
- Editorial: Defining each kind of built-in exotic in one place HOT 1
- update the colophon to mention new fonts
- update the description of enum presentation in 6.2.1
- Boolean interpretation to and from string HOT 3
- Small change feature request. HOT 7
- Cover grammar application should be more discoverable HOT 2
- [spam]
- Generator.prototype is not defined HOT 9
- Inconsistent "well known symbol" vs "well-known symbol" in Symbol.asyncIterator HOT 1
- Missing period in AsyncFunction.prototype.constructor section
- %GeneratorFunction.prototype.prototype.next% is not defined HOT 2
- "this value" and "NewTarget" no longer defined in Built-in Function Objects HOT 1
- `%TypedArray%.prototype.slice` does not completely account for the original TA's size changing HOT 3
- Encoding and decoding issues of `<script>` characters using decodeURIComponent and encodeURIComponent HOT 6
- Object invariants disallow changing non-configurable but writable data property's value HOT 7
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from ecma262.