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Module Blocks #7009

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Module Blocks #7009

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bc66e9d
Added one whole sentence about module blocks
surma Feb 5, 2021
ef3424f
Module map shenanigans
surma Feb 26, 2021
3d75040
Invoke create module script algorithm
surma Jul 22, 2021
c9f9827
Add HostInitializeModuleBlock hook implementation
surma Aug 5, 2021
a03face
Integrate ModuleBlocks with structured clone
surma Sep 2, 2021
b5a8425
Fix dynamic import TODO
surma Sep 2, 2021
ae2cf8d
Merge remote-tracking branch 'origin/main' into module-blocks
surma Sep 2, 2021
b8c430e
Minor cleanup
surma Sep 2, 2021
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130 changes: 95 additions & 35 deletions source
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Original file line number Diff line number Diff line change
Expand Up @@ -8328,6 +8328,16 @@ interface <dfn interface>DOMStringList</dfn> {
</ol>
</li>

<li>
<p>Otherwise, if <var>value</var> has [[ModuleBlockBody]] internal slot, then:</p>

<ol>
<li><p>Set <var>serialized</var> to { [[Type]]: "ModuleBlock",
[[ModuleBlockBody]]: <var>value</var>.[[ModuleBlockBody]],
[[HostDefined]]: <var>value</var>.[[HostDefined]] }.</p></li>
</ol>
</li>

<li>
<p>Otherwise, if <var>value</var> has an [[ErrorData]] internal slot and <var>value</var> is not
a <span>platform object</span>, then:</p>
Expand Down Expand Up @@ -8722,6 +8732,17 @@ o.myself = o;</code></pre>
</ol>
</li>

<li>
<p>Otherwise, if <var>serialized</var>.[[Type]] is "ModuleBlock", then:</p>

<ol>
<li><p>Set <var>value</var> to a new ModuleBlock object in <var>targetRealm</var>
whose [[ModuleBlockBody]] internal slot value is <var>value</var>.[[ModuleBlockBody]]
and whose [[HostDefined]] internal slot value is <var>value</var>.[[HostDefined]].</p></li>

</ol>
</li>

<li>
<p>Otherwise, if <var>serialized</var>.[[Type]] is "Array", then:</p>

Expand Down Expand Up @@ -90909,43 +90930,52 @@ document.querySelector("button").addEventListener("click", bound);
script</span> (on success).</p>

<ol>
<li><p>Let <var>url</var> be the result of <span data-x="resolve a module specifier">resolving a
<li><p>Let <var>specifier</var> be the result of <span data-x="resolve a module specifier">resolving a
module specifier</span> given <var>base URL</var> and <var>moduleRequest</var>.[[Specifier]].</p></li>

<li><p>If <var>url</var> is failure, then asynchronously complete this algorithm with null, and
return.</p></li>
<li>
<p>If <var>specifier</var> is a <span>module block</span>, then:</p>
<ol>
<li><p>Let <var>source text</var> be <var>specifier</var>.[[ModuleBlockBody]].</p></li>

<li><p>Assert: <var>moduleRequest</var>.[[Assertions]] does not contain any <span>Record</span>
<var>entry</var> such that <var>entry</var>.[[Key]] is not "<code data-x="">type</code>", because
we only asked for "<code data-x="">type</code>" assertions in
<span>HostGetSupportedImportAssertions</span>.</p></li>
<li><p>Let <var>module block base URL</var> be <var>specifier</var>.[[HostDefined]].</p></li>

<li><p>If <var>moduleRequest</var>.[[Assertions]] has a <span>Record</span> <var>entry</var>
such that <var>entry</var>.[[Key]] is "<code data-x="">type</code>", then let <var>module
type</var> be <var>entry</var>.[[Value]]. Otherwise let <var>module type</var> be "<code
data-x="">javascript</code>".</p></li>
<li><p>Let <var>result</var> be the result of <span>creating a module script</span> using
<var>source text</var>, <var>settings object</var>, <var>module block base URL</var>, and
<var>options</var>.</p></li>

<li><p>If <var>module type</var> is not "<code data-x="">javascript</code>", "<code
data-x="">css</code>", or "<code data-x="">json</code>", then asynchronously complete this
algorithm with null, and return.</p></li>
<li><p>Set <var>moduleMap</var>[<var>specifier</var>] to <var>module script</var>.</p></li>
</ol>
<p>else:</p>
<ol>
<li><p>Assert: <var>moduleRequest</var>.[[Assertions]] does not contain any <span>Record</span>
<var>entry</var> such that <var>entry</var>.[[Key]] is not "<code data-x="">type</code>", because
we only asked for "<code data-x="">type</code>" assertions in
<span>HostGetSupportedImportAssertions</span>.</p></li>

<li><p><span>Fetch a single module script</span> given <var>url</var>, <var>settings
object</var>, "<code data-x="">script</code>", <var>options</var>, <var>settings object</var>,
"<code data-x="">client</code>", <var>moduleRequest</var>, and with the
<var>top-level module fetch flag</var> set. If the caller of this algorithm specified custom
<span data-x="fetching-scripts-perform-fetch">perform the fetch</span> steps, pass those along as
well. Wait until the algorithm asynchronously completes with <var>result</var>.</p></li>
<li><p>If <var>moduleRequest</var>.[[Assertions]] has a <span>Record</span> <var>entry</var>
such that <var>entry</var>.[[Key]] is "<code data-x="">type</code>", then let <var>module
type</var> be <var>entry</var>.[[Value]]. Otherwise let <var>module type</var> be "<code
data-x="">javascript</code>".</p></li>

<li><p>If <var>result</var> is null, asynchronously complete this algorithm with null, and
return.</p></li>
<li><p>If <var>module type</var> is not "<code data-x="">javascript</code>", "<code
data-x="">css</code>", or "<code data-x="">json</code>", then asynchronously complete this
algorithm with null, and return.</p></li>

<li><p>Let <var>visited set</var> be « (<var>url</var>, <var>module type</var>) ».</p></li>
<li><p><span>Fetch a single module script</span> given <var>url</var>, <var>settings
object</var>, "<code data-x="">script</code>", <var>options</var>, <var>settings object</var>,
"<code data-x="">client</code>", <var>moduleRequest</var>, and with the
<var>top-level module fetch flag</var> set. If the caller of this algorithm specified custom
<span data-x="fetching-scripts-perform-fetch">perform the fetch</span> steps, pass those along as
well. Wait until the algorithm asynchronously completes with <var>result</var>.</p></li>
</ol>

<li><p><span data-x="fetch the descendants of and link a module script">Fetch the
descendants of and link</span> <var>result</var> given <var>settings object</var>,
<var>destination</var>, and <var>visited set</var>. When this asynchronously completes with
<var>final result</var>, asynchronously complete this algorithm with <var>final
result</var>.</p></li>
<li><p>Let <var>visited set</var> be « (<var>url</var>, <var>module type</var>) ».</p></li>
<li><p><span data-x="fetch the descendants of and link a module script">Fetch the
descendants of and link</span> <var>result</var> given <var>settings object</var>,
<var>destination</var>, and <var>visited set</var>. When this asynchronously completes with
<var>final result</var>, asynchronously complete this algorithm with <var>final
result</var>.</p></li>
</ol>

<p>To <dfn>fetch a modulepreload module script graph</dfn> given a <var>url</var>, a
Expand Down Expand Up @@ -92626,15 +92656,25 @@ dictionary <dfn dictionary>PromiseRejectionEventInit</dfn> : <span>EventInit</sp
</dl>

<p><span w-nodev>A <dfn>module map</dfn> is a <span data-x="ordered map">map</span> keyed by <span
data-x="tuple">tuples</span> consisting of a <span>URL record</span> and a <span>string</span>.
The <span>URL record</span> is the <span data-x="concept-request-url">request URL</span> at which
the module was fetched, and the <span>string</span> indicates the type of the module (e.g. "<code
data-x="">javascript</code>"). The <span>module map</span>'s values are either a <span>module
script</span>, null (used to represent failed fetches), or a placeholder value "<code
data-x="">fetching</code>". </span><span data-x="module map">Module maps</span> are used to ensure
that imported module scripts are only fetched, parsed, and evaluated once per
data-x="tuple">tuples</span>. The tuple consists of:</p>

<ol>
<li><p>A <span>URL record</span> or a <span>module block</span>.</p></li>
<li><p>A <span>string</span>.</p></li>
</ol>

<p>The <span>URL record</span> is the <span data-x="concept-request-url">request URL</span>
at which the module was fetched, and the <span>string</span> indicates the type of the module
(e.g. "<code data-x="">javascript</code>"). The <span>module map</span>'s values are either a
<span>module script</span>, null (used to represent failed fetches), or a placeholder value
"<code data-x="">fetching</code>". </span><span data-x="module map">Module maps</span> are used
to ensure that imported module scripts are only fetched, parsed, and evaluated once per
<code>Document</code> or <a href="#workers">worker</a>.</p>

<p>The module map is a weak map. The entries where tuple key has a module block are weakly held,
but tuple keys with the URL record keys are strongly held. This is because module block
instances may be collected throughout the lifetime of a realm.</p>

<div class="example">
<p>Since <span data-x="module map">module maps</span> are keyed by (URL, module type), the
following code will create three separate entries in the <span>module map</span>, since it
Expand Down Expand Up @@ -92951,6 +92991,26 @@ import "https://example.com/foo/../module2.mjs";</code></pre>
<li><p>Return <var>resolved module script</var>'s <span
data-x="concept-script-record">record</span>.</p></li>
</ol>
<h6><dfn>HostIntializeModuleBlock</dfn>(<var>moduleBlock</var>)</h6>

<p>JavaScript contains an <span>implementation-defined</span> <span
data-x="js-HostInitializeModuleBlock">HostIntializeModuleBlock</span> abstract operation. User
agents must use the following implementation: <ref spec=JAVASCRIPT></p>

<ol>
<li><p>Let <var>urlString</var> be null.</p></li>
<p>If <var>active script</var> is not null, then:</p>
<ol>
<li><p>If <var>active script</var>'s <var>base URL</var> is not null, then:</p></li>
<ol>
<li><p>Let <var>urlString</var> be <var>active script</var>'s <span
data-x="concept-script-base-url">base URL</span>, <span
data-x="concept-url-serializer">serialized</span>.</p></li>
</ol>
</ol>
</li>
<li><p>Set the <var>moduleBlock</var>.[[HostDefined]] to <var>urlString</var>.</p></li>
</ol>

<h6 id="hostgetsupportedimportassertions"><dfn>HostGetSupportedImportAssertions</dfn>()</h6>

Expand Down