Normative: Clarify text about host added properties #301
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@@ -357,10 +357,25 @@ <h1>Runtime Semantics: HostInitializeSyntheticRealm ( _realm_ )</h1> | |
| operation used to inform the host of any newly created realms from | ||
| the Realm constructor. Its return value is not used, though it may | ||
| throw an exception. The idea of this hook is to initialize host | ||
| data structures related to the Realm, e.g., for module loading. | ||
| </p> | ||
| <p> | ||
| The host may use this hook to add properties to the Realm's global | ||
| object. Those properties must each be configurable to provide | ||
| platform capabilities with no authority to cause side effects such | ||
| as I/O or mutation of values that are shared across different | ||
| realms within the same host environment. | ||
| </p> | ||
| <emu-note> | ||
| <p> | ||
| This specification does not recommend any specific addition. | ||
| In the Web embedding, HTML and WebIDL will specify which | ||
| interfaces are included. The Web Platform and Web-like | ||
| environments may decide to include `setTimeout`, `EventTarget`, | ||
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There was a problem hiding this comment. AFAIK setTimeout is IO. And as I explained in #284 I strongly against the host being able to add things into the realm without being able to have a clean version. This also hurts the API to be cross-platform safe. There was a problem hiding this comment. This is just an editorial note and we can remove the example. Anyway, please keep the discussion to the respective issue. |
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| `atob`, `TextEncoder`, `URL`, etc. while at the same time not | ||
| including `HTMLElement`, `console`, `localStorage`, `fetch`, etc.. | ||
| </p> | ||
| </emu-note> | ||
| </emu-clause> | ||
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| <emu-clause id="sec-hostimportmodulebindingdynamically" aoid="HostImportModuleBindingDynamically"> | ||
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This is not enough for the SES requirement.
Imagine the host provide a
counter { [[Get]]: () => #counter, [[Set]]: (val) => #counter = val }property on the Realm's global object, this provides a shared global state within the Realm (not shared across different realms). It provides a communication channel in the different compartments within the same realm.There was a problem hiding this comment.
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I guess I read the text to cover that case--I see the code sample as a value shared across realms, at a high level. I guess we just need to iterate on the wording so that it's maximally clear.
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If
#counteris a host-defined pre-realm internal state, it will be a mutable state within the Realm and passes the current spec text but violate the SES requirement.