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Web IDL study: detect event handlers with no matching even
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When an interface defines an event handler, there should always be an event
named after the event handler that targets the interface. The new `noEvent`
anomaly detects situations where the event is missing.

The analysis reports the two anomalies mentioned in:
w3c/webref#1216 (comment)

(The analysis reports additional anomalies when run on the raw extracts. That's
normal and due to missing event targets that get added during curation)
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@tidoust
tidoust committed Sep 11, 2024
1 parent a00f72f commit b0302b6
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Showing 3 changed files with 147 additions and 9 deletions.
57 changes: 50 additions & 7 deletions src/lib/study-webidl.js
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
*/

import * as WebIDL2 from 'webidl2';
import { getInterfaceTreeInfo } from 'reffy';

const getSpecs = list => [...new Set(list.map(({ spec }) => spec))];
const specName = spec => spec.shortname ?? spec.url;
Expand Down Expand Up @@ -174,6 +175,15 @@ function studyWebIdl (specs, { crawledResults = [], curatedResults = [] } = {})
const usedTypes = {}; // Index of types used in the IDL
const usedExtAttrs = {}; // Index of extended attributes

// We need to run the analysis on all specs, even if caller is only
// interested in a few of them, because types may be defined in specs that
// the caller is not interested in.
const allSpecs = (crawledResults.length > 0) ? crawledResults : specs;
const allEvents = allSpecs
.filter(spec => Array.isArray(spec.events))
.map(spec => spec.events.map(e => Object.assign({ spec }, e)))
.flat();

// Record an anomaly for the given spec(s),
// provided we are indeed interested in the results
function recordAnomaly (spec, name, message) {
Expand All @@ -193,17 +203,54 @@ function studyWebIdl (specs, { crawledResults = [], curatedResults = [] } = {})
function inheritsFrom (iface, ancestor) {
if (!iface.inheritance) return false;
if (iface.inheritance === ancestor) return true;
if (!dfns[iface.inheritance]) return false;
const parentInterface = dfns[iface.inheritance].find(({ idl }) => !idl.partial)?.idl;
if (!parentInterface) return false;
return inheritsFrom(parentInterface, ancestor);
}

function getBubblingPath(iface) {
const interfaces = Object.values(dfns)
.map(dfn => dfn.find(d => d.idl.type === 'interface'))
.filter(dfn => !!dfn)
.map(dfn => dfn.idl);
const { bubblingPath } = getInterfaceTreeInfo(iface, interfaces);
return bubblingPath;
}

// TODO: a full check of event handlers would require:
// - checking if the interface doesn't include a mixin with eventhandlers
function checkEventHandlers (spec, memberHolder, iface = memberHolder) {
const eventHandler = memberHolder.members.find(m => m?.name?.startsWith('on') && m.type === 'attribute' && m.idlType?.idlType === 'EventHandler');
if (eventHandler && !inheritsFrom(iface, 'EventTarget')) {
recordAnomaly(spec, 'unexpectedEventHandler', `The interface \`${iface.name}\` defines an event handler \`${eventHandler.name}\` but does not inherit from \`EventTarget\``);
const eventHandlers = memberHolder.members.filter(m => m?.name?.startsWith('on') && m.type === 'attribute' && m.idlType?.idlType === 'EventHandler');
if (eventHandlers.length > 0 && !inheritsFrom(iface, 'EventTarget')) {
recordAnomaly(spec, 'unexpectedEventHandler', `The interface \`${iface.name}\` defines an event handler \`${eventHandlers[0].name}\` but does not inherit from \`EventTarget\``);
}

for (const eventHandler of eventHandlers) {
const eventType = eventHandler.name.substring(2);
const events = allEvents.filter(e => e.type === eventType);
let event = events.find(e => e.targets?.find(target =>
target === iface.name));
if (!event) {
// No event found with the same type that targets the interface
// directly, but one the events may target an interface that
// inherits from the interface, or may bubble on the interface.
event = events.find(e => e.targets?.find(target => {
const inheritanceFound = dfns[target]?.find(dfn =>
dfn.idl.type === 'interface' &&
inheritsFrom(dfn.idl, iface.name));
if (inheritanceFound) return true;
if (!e.bubbles) return false;
const bubblingPath = getBubblingPath(target);
if (!bubblingPath) return false;
return bubblingPath.find(bubblingIface =>
iface.name === bubblingIface ||
inheritsFrom(iface, bubblingIface));
}));
}
if (!event) {
recordAnomaly(spec, 'noEvent', `The interface \`${iface.name}\` defines an event handler \`${eventHandler.name}\` but no event named "${eventType}" targets it`);
}
}
}

Expand Down Expand Up @@ -384,10 +431,6 @@ function studyWebIdl (specs, { crawledResults = [], curatedResults = [] } = {})
}
}

// We need to run the analysis on all specs, even if caller is only
// interested in a few of them, because types may be defined in specs that
// the caller is not interested in.
const allSpecs = (crawledResults.length > 0) ? crawledResults : specs;
allSpecs
// We're only interested in specs that define Web IDL content
.filter(spec => !!spec.idl)
Expand Down
5 changes: 5 additions & 0 deletions src/lib/study.js
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Original file line number Diff line number Diff line change
Expand Up @@ -149,6 +149,11 @@ const anomalyGroups = [
guidance: 'See the [`[Exposed]`](https://webidl.spec.whatwg.org/#Exposed) extended attribute section in Web IDL for requirements.'
},
{ name: 'invalid', title: 'Invalid Web IDL' },
{
name: 'noEvent',
title: 'Suspicious event handlers',
description: 'The following suspicious event handlers were found'
},
{ name: 'noExposure', title: 'Missing `[Exposed]` attributes' },
{ name: 'noOriginalDefinition', title: 'Missing base interfaces' },
{ name: 'overloaded', title: 'Invalid overloaded operations' },
Expand Down
94 changes: 92 additions & 2 deletions test/study-webidl.js
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Original file line number Diff line number Diff line change
Expand Up @@ -148,7 +148,7 @@ interface WhereIAm {};
});
});

it('reports no anomaly for valid EventHandler attributes definitions', () => {
it('reports EventHandler attributes with no matching events', () => {
const report = analyzeIdl(`
[Exposed=*]
interface Event {};
Expand All @@ -163,6 +163,34 @@ interface Carlos : EventTarget {
[Exposed=*]
interface EventTarget {};
`);
assertNbAnomalies(report, 1);
assertAnomaly(report, 0, {
name: 'noEvent',
message: 'The interface `Carlos` defines an event handler `onbigbisous` but no event named "bigbisous" targets it'
});
});

it('reports no anomaly for valid EventHandler attributes definitions', () => {
const crawlResult = toCrawlResult(`
[Exposed=*]
interface Event {};
[LegacyTreatNonObjectAsNull]
callback EventHandlerNonNull = any (Event event);
typedef EventHandlerNonNull? EventHandler;
[Global=Window,Exposed=*]
interface Carlos : EventTarget {
attribute EventHandler onbigbisous;
};
[Exposed=*]
interface EventTarget {};
`);
crawlResult[0].events = [{
type: 'bigbisous',
interface: 'Event',
targets: ['Carlos']
}];
const report = study(crawlResult);
assertNbAnomalies(report, 0);
});

Expand All @@ -179,11 +207,73 @@ interface Carlos {
attribute EventHandler onbigbisous;
};
`);
assertNbAnomalies(report, 1);
assertNbAnomalies(report, 2);
assertAnomaly(report, 0, {
name: 'unexpectedEventHandler',
message: 'The interface `Carlos` defines an event handler `onbigbisous` but does not inherit from `EventTarget`'
});
assertAnomaly(report, 1, { name: 'noEvent' });
});

it('follows the inheritance chain to assess event targets', () => {
const crawlResult = toCrawlResult(`
[Exposed=*]
interface Event {};
[LegacyTreatNonObjectAsNull]
callback EventHandlerNonNull = any (Event event);
typedef EventHandlerNonNull? EventHandler;
[Global=Window,Exposed=*]
interface Singer : EventTarget {
attribute EventHandler onbigbisous;
};
[Global=Window,Exposed=*]
interface Carlos : Singer {};
[Exposed=*]
interface EventTarget {};
`);
crawlResult[0].events = [{
type: 'bigbisous',
interface: 'Event',
targets: [
'Carlos'
]
}];
const report = study(crawlResult);
assertNbAnomalies(report, 0);
});

it('follows the bubbling path to assess event targets', () => {
const crawlResult = toCrawlResult(`
[Exposed=*]
interface Event {};
[LegacyTreatNonObjectAsNull]
callback EventHandlerNonNull = any (Event event);
typedef EventHandlerNonNull? EventHandler;
[Global=Window,Exposed=*]
interface IDBDatabase : EventTarget {
attribute EventHandler onabort;
};
[Global=Window,Exposed=*]
interface IDBTransaction : EventTarget {
attribute EventHandler onabort;
};
[Global=Window,Exposed=*]
interface MyIndexedDB : IDBDatabase {
};
[Exposed=*]
interface EventTarget {};`);
crawlResult[0].events = [{
type: 'abort',
interface: 'Event',
targets: ['IDBTransaction'],
bubbles: true
}];
const report = study(crawlResult);
assertNbAnomalies(report, 0);
});

it('detects incompatible partial exposure issues', () => {
Expand Down

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