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Add hooks for HTML
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"legacy-clone a browsing session storage shed" can be used by HTML to define creation of auxiliary browsing contexts, as part of whatwg/html#5560.

"obtain a storage key" can be used by APIs that share keying logic with storage, such as BroadcastChannel and shared workers. See whatwg/html#3054. It's potentially also useful for Indexed DB as discussed in w3c/IndexedDB#334.

Also helps a bit with #95 by reorganizing and adding some more detail to how a user agent is supposed to manage storage.

Closes #92.
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@annevk
annevk authored Jun 5, 2020
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Expand Up @@ -84,8 +84,8 @@ function retrieveNextChunk(nextChunkInfo) {

<p>This specification depends on the Infra Standard. [[!INFRA]]

<p>This specification uses terminology from the DOM, HTML, IDL, Permissions API, and URL Standards.
[[DOM]] [[HTML]] [[WEBIDL]] [[PERMISSIONS]] [[URL]]
<p>This specification uses terminology from the HTML, IDL, and Permissions Standards.
[[!HTML]] [[!WEBIDL]] [[!PERMISSIONS]]



Expand Down Expand Up @@ -195,13 +195,30 @@ anticipated that some APIs will be applicable to both <a>storage types</a> going
<!-- If that does not happen by 2024 we probably ought to admit defeat and simplify this a bit. -->


<h3 id=storage-sheds>Storage sheds</h3>
<h3 id=storage-keys>Storage keys</h3>

<p>A <dfn>storage key</dfn> is an <a for=/>origin</a>. [[HTML]]
<p>A <dfn>storage key</dfn> is an <a for=/>origin</a>. [[!HTML]]

<p class=XXX>This is expected to change, see
<p class=XXX>This is expected to change; see
<a href="https://privacycg.github.io/storage-partitioning/">Client-Side Storage Partitioning</a>.

<p>To <dfn export>obtain a storage key</dfn>, given an <a>environment settings object</a>
<var>environment</var>, run these steps:

<ol>
<li><p>Let <var>key</var> be <var>environment</var>'s
<a for="environment settings object">origin</a>.

<li><p>If <var>key</var> is an <a>opaque origin</a>, then return failure.

<li><p>If the user has disabled storage, then return failure.

<li><p>Return <var>key</var>.
</ol>


<h3 id=storage-sheds>Storage sheds</h3>

<p>A <dfn>storage shed</dfn> is a <a for=/>map</a> of <a>storage keys</a> to <a>storage shelves</a>.
It is initially empty.

Expand All @@ -211,15 +228,36 @@ It is initially empty.
<a for=/>storage shed</a>. A user agent's <a for="user agent">storage shed</a> holds all
<dfn>local storage</dfn> data.

<p>A browsing session holds a <dfn for="browsing session">storage shed</dfn>, which is a
<a for=/>storage shed</a>. A browsing session's <a for="browsing session">storage shed</a> holds all
<dfn>session storage</dfn> data.
<p>A <a for=/>browsing session</a> holds a <dfn for="browsing session">storage shed</dfn>, which is
a <a for=/>storage shed</a>. A <a for=/>browsing session</a>'s
<a for="browsing session">storage shed</a> holds all <dfn>session storage</dfn> data.

<p>To <dfn export>legacy-clone a browsing session storage shed</dfn>, given a
<a for=/>browsing session</a> <var>A</var> and a <a for=/>browsing session</a> <var>B</var>, run
these steps:

<ol>
<li>
<p><a for=map>For each</a> <var>key</var> → <var>shelf</var> of <var>A</var>'s
<a for="browsing session">storage shed</a>:

<ol>
<li><p>Let <var>newShelf</var> be the result of running <a>create a storage shelf</a> with
"<code>session</code>".

<li><p>Set <var>newShelf</var>'s <a>bucket map</a>["<code>default</code>"]'s
<a>bottle map</a>["<code>sessionStorage</code>"]'s <a for="storage bottle">map</a> to a
<a for=map>clone</a> of <var>shelf</var>'s <a>bucket map</a>["<code>default</code>"]'s
<a>bottle map</a>["<code>sessionStorage</code>"]'s <a for="storage bottle">map</a>.

<li><p>Set <var>B</var>'s <a for="browsing session">storage shed</a>[<var>key</var>] to
<var>newShelf</var>.
</ol>
</ol>

<p class="XXX" id=lack-of-browsing-session>See
<a href="https://github.com/whatwg/html/issues/4782">whatwg/html issue #4782</a> and
<a href="https://github.com/whatwg/html/issues/5350">whatwg/html issue #5350</a> for defining
browsing session. It is roughly analogous to <a>top-level browsing context</a> except that it cannot
be replaced due to <code>Cross-Origin-Opener-Policy</code> or navigation.
<p class="note">This is considered legacy as the benefits, if any, do not outweigh the
implementation complexity. And therefore it will not be expanded or used outside of
<cite>HTML</cite>. [[HTML]]


<h3 id=storage-shelves>Storage shelves</h3>
Expand All @@ -238,24 +276,14 @@ given a <a for=map>value</a> when a <a>storage shelf</a> is
<var>type</var>, run these steps:

<ol>
<li><p>Let <var>key</var> be <var>environment</var>'s
<a for="environment settings object">origin</a>.

<li><p>If <var>key</var> is an <a>opaque origin</a>, then return failure.

<li><p>If the user has disabled storage, then return failure.

<li>
<p>If <var>shed</var>[<var>key</var>] does not <a for=map>exist</a>, then:

<ol>
<li><p>Let <var>shelf</var> be a new <a>storage shelf</a>.
<li><p>Let <var>key</var> be the result of running <a>obtain a storage key</a> with
<var>environment</var>.

<li><p>Set <var>shelf</var>'s <a>bucket map</a>["<code>default</code>"] to the result of
<a>create a storage bucket</a> with <var>type</var>.
<li><p>If <var>key</var> is failure, then return failure.

<li><p>Set <var>shed</var>[<var>key</var>] to <var>shelf</var>.
</ol>
<li><p>If <var>shed</var>[<var>key</var>] does not <a for=map>exist</a>, then set
<var>shed</var>[<var>key</var>] to the result of running <a>create a storage shelf</a> with
<var>type</var>.

<li><p>Return <var>shed</var>[<var>key</var>].
</ol>
Expand All @@ -264,12 +292,22 @@ given a <a for=map>value</a> when a <a>storage shelf</a> is
<var>environment</var>, return the result of running <a>obtain a storage shelf</a> with the user
agent's <a for="user agent">storage shed</a>, <var>environment</var>, and "<code>local</code>".

<p>To <dfn>create a storage shelf</dfn>, given a <a>storage type</a> <var>type</var>, run these
steps:

<ol>
<li><p>Let <var>shelf</var> be a new <a>storage shelf</a>.

<li><p>Set <var>shelf</var>'s <a>bucket map</a>["<code>default</code>"] to the result of running
<a>create a storage bucket</a> with <var>type</var>.

<li><p>Return <var>shelf</var>.
</ol>


<h3 id=buckets oldids=boxes>Storage buckets</h3>

<p>A <dfn>storage bucket</dfn> is a place for <a>storage endpoints</a> to store data. Whenever a
<a>storage bucket</a> is cleared by the user agent, it must be cleared in its entirety.
<!-- This is probably better defined in some kind of storage lifetime section. -->
<p>A <dfn>storage bucket</dfn> is a place for <a>storage endpoints</a> to store data.

<p>A <a>storage bucket</a> has a <dfn>bottle map</dfn> of <a>storage identifiers</a> to
<a>storage bottles</a>.
Expand Down Expand Up @@ -352,7 +390,7 @@ standard and standards using this standard can access the contents.
<li><p>Assert: <var>type</var> is "<code>session</code>".

<li><p>Set <var>shed</var> to <var>environment</var>'s
<a class=XXX href=#lack-of-browsing-session>browsing session</a>'s
<a for="environment settings object">browsing session</a>'s
<a for="browsing session">storage shed</a>.
</ol>

Expand Down Expand Up @@ -450,28 +488,45 @@ evaluating quotas.



<h2 id=ui-guidelines>User Interface Guidelines</h2>
<h2 id=management>Management</h2>

<p>Whenever a <a>storage bucket</a> is cleared by the user agent, it must be cleared in its
entirety. User agents should avoid clearing <a>storage buckets</a> while script that is able to
access them is running, unless instructed otherwise by the user.

<p>If removal of <a>storage buckets</a> leaves the encompassing <a>storage shelf</a>'s
<a>bucket map</a> <a for=map lt="is empty">empty</a>, then <a for=map>remove</a> that
<a>storage shelf</a> and corresponding <a>storage key</a> from the encompassing
<a for=/>storage shed</a>.


<h3 id=storage-pressure>Storage pressure</h3>

<p>A user agent that comes under storage pressure should clear network state and
<a>local storage buckets</a> whose <a for="local storage bucket">mode</a> is
"<code>best-effort</code>", ideally prioritizing removal in a manner that least impacts the user.

<p>If a user agent continues to be under storage pressure, then the user agent should inform the
user and offer a way to clear the remaining <a>local storage buckets</a>, i.e., those whose
<a for="local storage bucket">mode</a> is "<code>persistent</code>".

<p><a>Session storage buckets</a> must be cleared as <a for=/>browsing sessions</a> are closed.

<p class="note">If the user agent allows for revival of <a for=/>browsing sessions</a>, e.g.,
through reopening <a for=/>browsing sessions</a> or continued use of them after restarting the user
agent, then clearing necessarily involves a more complex set of heuristics.


<h3 id=ui-guidelines>User interface guidelines</h3>

<p>User agents should not distinguish between network state and storage in their user interface.
Instead user agents should offer users the ability to remove all storage for each group of
Instead user agents should offer users the ability to clear all storage for each group of
<a>schemelessly same site</a> <a for=/>origins</a>. This ensures to some extent that network state
cannot be used to revive storage. This also reduces the amount users need to know about the
different ways in which websites can store data.
<!-- To some extent, since HTTP ETag... And also, permissions/credentials, maybe? -->

<p>Credentials should be separated as they contain data the user might not be able to revive, such
as an autogenerated password. Permissions are best separated too to avoid inconveniencing the user.
Credentials and permissions are also somewhat easier to understand and differentiate for users from
network state and storage.


<h3 id=storage-pressure>Storage Pressure</h3>

<p>When the user agent notices it comes under storage pressure and it cannot free up sufficient
space by clearing network state, <a>session storage buckets</a>, and <a>local storage buckets</a>
whose <a for="local storage bucket">mode</a> is "<code>best-effort</code>", then the user agent
should inform the user and offer a way to clear the remaining <a>local storage buckets</a>, i.e.,
those whose <a for="local storage bucket">mode</a> is "<code>persistent</code>".



Expand All @@ -486,7 +541,7 @@ Navigator includes NavigatorStorage;
WorkerNavigator includes NavigatorStorage;
</pre>

<p>Each <a>environment settings object</a> has an associated {{StorageManager}} object. [[HTML]]
<p>Each <a>environment settings object</a> has an associated {{StorageManager}} object. [[!HTML]]

<p>The <dfn attribute for=NavigatorStorage><code>storage</code></dfn> getter steps are to return
<a>this</a>'s <a>relevant settings object</a>'s {{StorageManager}} object.
Expand Down

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