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Fix error cases of <script type=module>
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There are several different ways things can go wrong with
<script type=module>. In order from earliest to latest, for a single
module script, they are:

- Fetching failures
- Parsing failures
- Invalid module specifiers
- Instantiation failures
- Evaluation failures

This tweaks the way that these errors interact, to ensure that fetching
failures are treated one way, causing the <script>'s "error" event to
fire, and the other failures are uniformly treated as errors running the
script, causing the global's "error" event to fire.

This also makes it clear that when fetching descendant module scripts,
you can bail out early if one of them fails to fetch or has previously
been discovered to be errored.

Evaluation failures are particularly tricky for dependencies, as usually
ModuleEvaluation() is a no-op if it has happened previously
(either successfully or not). This is discussed in more depth in
tc39/ecma262#862. To work around this, we need
to store the evaluation error, if one occurs, similar to what we already
do for instantiation errors.

Fixes whatwg#2567.

However, there are still problems with this setup, which may need
further infrastructure changes; see:

- whatwg#2595 (comment)
- whatwg#2629
- whatwg#2630

But for now the improvement given by this commit is enough to merge it.
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@domenic
domenic authored and Alice Boxhall committed Jan 7, 2019
1 parent 4330abb commit 101fe60
Showing 1 changed file with 121 additions and 80 deletions.
201 changes: 121 additions & 80 deletions source
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Original file line number Diff line number Diff line change
Expand Up @@ -86557,24 +86557,24 @@ interface <dfn>NavigatorOnLine</dfn> {

</dd>

<dt>An <dfn data-x="concept-module-script-instantiation-state">instantiation state</dfn></dt>
<dt>A <dfn data-x="concept-module-script-state">state</dfn></dt>

<dd>

<p>One of "<code data-x="">uninstantiated</code>", "<code data-x="">errored</code>", or "<code
data-x="">instantiated</code>", used to prevent reinvocation of <span
data-x="js-ModuleDeclarationInstantiation">ModuleDeclarationInstantiation</span> on modules that
failed to instantiate previously.</p>
failed to instantiate previously, and to ensure errors during parsing, instantiation, or
evaluation are remembered and propagated correctly.</p>

</dd>

<dt>An <dfn data-x="concept-module-script-instantiation-error">instantiation error</dfn></dt>
<dt>An <dfn data-x="concept-module-script-error">error</dfn></dt>

<dd>

<p>A JavaScript value, which has meaning only if the <span
data-x="concept-module-script-instantiation-state">instantiation state</span> is "<code
data-x="">errored</code>".</p>
data-x="concept-module-script-state">state</span> is "<code data-x="">errored</code>".</p>

</dd>

Expand Down Expand Up @@ -86607,6 +86607,33 @@ interface <dfn>NavigatorOnLine</dfn> {

</dl>

<p>To <dfn>error a module script</dfn> <var>script</var> with a given value <var>error</var>,
perform the following steps:</p>

<ol>
<li><p>Assert: <var>script</var>'s <span data-x="concept-module-script-state">state</span> is not
"<code data-x="">errored</code>".</p></li>

<li>
<p>If <var>script</var>'s <span data-x="concept-module-script-module-record">module
record</span> is set, then:</p>

<ol>
<li><p>Set <var>script</var> <span data-x="concept-module-script-module-record">module
record</span>'s [[HostDefined]] field to undefined.</p></li>

<li><p>Set <var>script</var>'s <span data-x="concept-module-script-module-record">module
record</span> to null.</p></li>
</ol>
</li>

<li><p>Set <var>script</var>'s <span data-x="concept-module-script-state">state</span> to
"<code data-x="">errored</code>".</p></li>

<li><p>Set <var>script</var>'s <span data-x="concept-module-script-error">error</span> to
<var>error</var>.</p></li>
</ol>

<hr>

<p>An <dfn data-export="">environment</dfn> is an object that identifies the settings of a
Expand Down Expand Up @@ -87041,73 +87068,49 @@ interface <dfn>NavigatorOnLine</dfn> {
<li><p>If <var>result</var> is null, asynchronously complete this algorithm with null and abort
these steps.</p></li>

<li><p>If <var>result</var>'s <span data-x="concept-module-script-state">state</span> is "<code
data-x="">instantiated</code>" or "<code data-x="">errored</code>", asynchronously complete this
algorithm with <var>result</var>, and abort these steps.</p></li>

<li><p>Assert: <var>result</var>'s <span data-x="concept-module-script-state">state</span> is
"<code data-x="">uninstantiated</code>".</p></li>

<li>
<p>Otherwise, <var>result</var> is a <span>module script</span>. <span data-x="fetch the
descendants of a module script">Fetch the descendants</span> of <var>result</var> given
<var>destination</var> and an ancestor list obtained by appending <var>url</var> to <var>ancestor
list</var>. Wait for <span data-x="fetch the descendants of a module script">fetching the
descendants of a module script</span> to asynchronously complete with <var>descendants
result</var> before proceeding to the next step.</p>
<p><span data-x="fetch the descendants of a module script">Fetch the
descendants</span> of <var>result</var> given <var>destination</var> and an ancestor list
obtained by appending <var>url</var> to <var>ancestor list</var>. Wait for <span data-x="fetch
the descendants of a module script">fetching the descendants of a module script</span> to
asynchronously complete with <var>descendants result</var> before proceeding to the next step.</p>

<p class="note">If the asynchronous completion result is null, meaning that fetching one of the
descendants failed, we still proceed through the next set of steps. A failure will shortly occur
during instantiation, which we then react to appropriately. The error signal is eventually
propagated to the caller of this algorithm in the last step.</p>
</li>

<li><p>Let <var>instantiationStatus</var> be null.</p></li>

<li><p>If <var>result</var>'s <span data-x="concept-module-script-instantiation-state">instantiation
state</span> is "<code data-x="">errored</code>", then set <var>instantiationStatus</var> to
Completion { [[Type]]: throw, [[Value]]: <var>result</var>'s <span
data-x="concept-module-script-instantiation-error">instantiation error</span>, [[Target]]:
empty }.</p></li>
<li><p>Let <var>record</var> be <var>result</var>'s <span
data-x="concept-module-script-module-record">module record</span>.</p></li>

<li>
<p>Otherwise:</p>

<ol>
<li><p>Let <var>record</var> be <var>result</var>'s <span
data-x="concept-module-script-module-record">module record</span>.</p></li>

<li>
<p>Set <var>instantiationStatus</var> to <var>record</var>.<span
data-x="js-ModuleDeclarationInstantiation">ModuleDeclarationInstantiation</span>().</p>
<p>Let <var>instantiationStatus</var> be <var>record</var>.<span
data-x="js-ModuleDeclarationInstantiation">ModuleDeclarationInstantiation</span>().</p>

<p class="note">This step will recursively call <span
data-x="js-ModuleDeclarationInstantiation">ModuleDeclarationInstantiation</span> all of the
module's uninstantiated dependencies.</p>
</li>
</ol>
<p class="note">This step will recursively call <span
data-x="js-ModuleDeclarationInstantiation">ModuleDeclarationInstantiation</span> all of the
module's uninstantiated dependencies.</p>
</li>

<li>
<p>For each <var>script</var> in <var>result</var>'s <span>uninstantiated inclusive descendant module
scripts</span>, perform the following steps:</p>
<p>For each <var>script</var> in <var>result</var>'s <span>uninstantiated inclusive descendant
module scripts</span>, perform the following steps:</p>

<ol>
<li>
<p>If <var>instantiationStatus</var> is an abrupt completion, then:</p>

<ol>
<li><p>Set <var>script</var> <span data-x="concept-module-script-module-record">module
record</span>'s [[HostDefined]] field to undefined.</p></li>

<li><p>Set <var>script</var>'s <span data-x="concept-module-script-module-record">module
record</span> to null.</p></li>

<li><p>Set <var>script</var>'s <span
data-x="concept-module-script-instantiation-state">instantiation state</span> to "<code
data-x="">errored</code>".</p></li>

<li><p>Set <var>script</var>'s <span
data-x="concept-module-script-instantiation-error">instantiation error</span> to
<var>instantiationStatus</var>.[[Value]].</p></li>
</ol>
</li>
<li><p>If <var>instantiationStatus</var> is an abrupt completion, then <span data-x="error a
module script">error</span> <var>script</var> with
<var>instantiationStatus</var>.[[Value]].</p></li>

<li><p>Otherwise, set <var>script</var>'s <span
data-x="concept-module-script-instantiation-state">instantiation state</span> to "<code
data-x="concept-module-script-state">state</span> to "<code
data-x="">instantiated</code>".</p></li>
</ol>
</li>
Expand All @@ -87125,6 +87128,9 @@ interface <dfn>NavigatorOnLine</dfn> {
data-x="module script">module scripts</span> determined as follows:</p>

<ol>
<li><p>If <var>script</var>'s <span data-x="concept-module-script-module-record">module
record</span> is null, return the empty set.</p></li>

<li><p>Let <var>moduleMap</var> be <var>script</var>'s <span>settings object</span>'s
<span data-x="concept-settings-object-module-map">module map</span>.</p></li>

Expand Down Expand Up @@ -87183,7 +87189,7 @@ interface <dfn>NavigatorOnLine</dfn> {
</li>

<li><p>Return a <span>set</span> containing all items of <var>inclusive descendants</var> whose
<span data-x="concept-module-script-instantiation-state">instantiation state</span> is "<code
<span data-x="concept-module-script-state">state</span> is "<code
data-x="">uninstantiated</code>".</p></li>
</ol>

Expand Down Expand Up @@ -87316,10 +87322,11 @@ interface <dfn>NavigatorOnLine</dfn> {
<ol>
<li><p>Let <var>error</var> be a new <code>TypeError</code> exception.</p></li>

<li><p><span>Report the exception</span> <var>error</var> for <var>module
script</var>.</p></li>
<li><p><span data-x="error a module script">Error</span> <var>module script</var> with
<var>error</var>.</p></li>

<li><p>Abort this algorithm, and asynchronously complete it with null.</p></li>
<li><p>Abort this algorithm, and asynchronously complete it with <var>module
script</var>.</p></li>
</ol>
</li>

Expand All @@ -87342,10 +87349,25 @@ interface <dfn>NavigatorOnLine</dfn> {
<span data-x="fetching-scripts-perform-fetch">perform the fetch</span> steps, pass those along
while performing the <span>internal module script graph fetching procedure</span>.</p>

<p>Wait for all of the <span>internal module script graph fetching procedure</span> invocations
to asynchronously complete. If any of them asynchronously complete with null, then
asynchronously complete this algorithm with null. Otherwise, asynchronously complete this
algorithm with <var>module script</var>.</p>
<p>These invocations of the <span>internal module script graph fetching procedure</span> should
be performed in parallel to each other.</p>

<p>If any invocation of the <span>internal module script graph fetching procedure</span>
asynchronously completes with null, optionally abort all other invocations, and then
asynchronously complete this algorithm with null.</p>

<p>If any invocation of the <span>internal module script graph fetching procedure</span>
asynchronously completes with a <span>module script</span> whose <span
data-x="concept-module-script-state">state</span> is "<code data-x="">errored</code>",
optionally abort all other invocations, and then asynchronously complete this algorithm with
<var>module script</var>. (The errored descendant will cause errors later in the module-fetching
process, but for now we treat it as a premature "success".)</p>

<p>Otherwise, wait for all of the <span>internal module script graph fetching procedure</span>
invocations to asynchronously complete, with <span data-x="module script">module scripts</span>
whose <span data-x="concept-module-script-state">states</span> are not "<code
data-x="">errored</code>". Then, asynchronously complete this algorithm with <var>module
script</var>.</p>
</li>
</ol>

Expand Down Expand Up @@ -87406,9 +87428,19 @@ interface <dfn>NavigatorOnLine</dfn> {
<var>result</var>.[[HostDefined]] will be <var>script</var>.</p>
</li>

<li><p>If <var>result</var> is a <span>List</span> of errors, <span>report the exception</span>
given by the first element of <var>result</var> for <var>script</var>, return null, and abort
these steps.</p></li>
<li>
<p>If <var>result</var> is a <span>List</span> of errors, then:</p>

<ol>
<li><p><span data-x="error a module script">Error</span> <var>script</var> with
<var>errors</var>[0].</p></li>

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

<li><p>Set <var>script</var>'s <span data-x="concept-module-script-state">state</span> to "<code
data-x="">uninstantiated</code>".</p></li>

<li><p>Set <var>script</var>'s <span data-x="concept-module-script-module-record">module
record</span> to <var>result</var>.</p></li>
Expand Down Expand Up @@ -87506,14 +87538,12 @@ interface <dfn>NavigatorOnLine</dfn> {
<li><p><span>Check if we can run script</span> with <var>settings</var>. If this returns "do
not run" then abort these steps.</p></li>

<li><p>If <var>s</var>'s <span data-x="concept-module-script-instantiation-state">instantiation
state</span> is "<code data-x="">errored</code>", then <span>report the
exception</span> given by <var>s</var>'s <span
data-x="concept-module-script-instantiation-error">instantiation error</span> for <var>s</var>
and abort these steps.</p></li>
<li><p>If <var>s</var>'s <span data-x="concept-module-script-state">state</span> is "<code
data-x="">errored</code>", then <span>report the exception</span> given by <var>s</var>'s <span
data-x="concept-module-script-error">error</span> for <var>s</var> and abort these
steps.</p></li>

<li><p>Assert: <var>s</var>'s <span
data-x="concept-module-script-instantiation-state">instantiation state</span> is "<code
<li><p>Assert: <var>s</var>'s <span data-x="concept-module-script-state">state</span> is "<code
data-x="">instantiated</code>" (and thus its <span
data-x="concept-module-script-module-record">module record</span> is not null).</p></li>

Expand All @@ -87527,13 +87557,24 @@ interface <dfn>NavigatorOnLine</dfn> {
data-x="js-ModuleEvaluation">ModuleEvaluation</span>().</p>

<p class="note">This step will recursively evaluate all of the module's dependencies.</p>

<p>If <span data-x="js-ModuleEvaluation">ModuleEvaluation</span> fails to complete as a result
of the user agent <span data-x="abort a running script">aborting the running script</span>, then
set <var>evaluationStatus</var> to Completion { [[Type]]: throw, [[Value]]: a new
<span>"<code>QuotaExceededError</code>"</span> <code>DOMException</code>, [[Target]]: empty }.
</li>

<li><p>If <var>evaluationStatus</var> is an abrupt completion, then <span>report the
exception</span> given by <var>evaluationStatus</var>.[[Value]] for <var>s</var>. (Do not perform
this step if <span data-x="js-ModuleEvaluation">ModuleEvaluation</span> fails to complete as a
result of the user agent <span data-x="abort a running script">aborting the running
script</span>.)</p></li>
<li>
<p>If <var>evaluationStatus</var> is an abrupt completion, then:</p>

<ol>
<li><p><span data-x="error a module script">Error</span> <var>script</var> with
<var>evaluationStatus</var>.[[Value]].</p></li>

<li><p><span>Report the exception</span> given by <var>evaluationStatus</var>.[[Value]] for
<var>s</var>.</p>
</ol>
</li>

<li><p><span>Clean up after running script</span> with <var>settings</var>.</p></li>
</ol>
Expand Down Expand Up @@ -88389,9 +88430,9 @@ import "https://example.com/foo/../module2.js";</pre>
steps.</p></li>

<li><p>If <var>resolved module script</var>'s <span
data-x="concept-module-script-instantiation-state">instantiation state</span> is "<code
data-x="">errored</code>", then throw <var>resolved module script</var>'s <span
data-x="concept-module-script-instantiation-error">instantiation error</span>.</p></li>
data-x="concept-module-script-state">state</span> is "<code data-x="">errored</code>", then throw
<var>resolved module script</var>'s <span
data-x="concept-module-script-error">error</span>.</p></li>

<li><p>Assert: <var>resolved module script</var>'s <span
data-x="concept-module-script-module-record">module record</span> is not null.</p></li>
Expand Down

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