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core(font-display): more accurately follow CSS spec #7191

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merged 4 commits into from
Feb 12, 2019
Merged

core(font-display): more accurately follow CSS spec #7191

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834838f
core(font-display): allow missing semicolon
patrickhulce Feb 8, 2019
7c51090
lint
patrickhulce Feb 8, 2019
c7dd90e
tighten up the whole audit
patrickhulce Feb 11, 2019
9377384
move whitespace out of capture group
patrickhulce Feb 11, 2019
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8 changes: 5 additions & 3 deletions lighthouse-core/audits/font-display.js
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@

const Audit = require('./audit');
const URL = require('../lib/url-shim').URL;
const PASSING_FONT_DISPLAY_REGEX = /block|fallback|optional|swap/;
const PASSING_FONT_DISPLAY_REGEX = /^(block|fallback|optional|swap)$/;
const CSS_URL_REGEX = /url\((.*?)\)/;
const CSS_URL_GLOBAL_REGEX = new RegExp(CSS_URL_REGEX, 'g');
const i18n = require('../lib/i18n/i18n.js');
Expand Down Expand Up @@ -57,11 +57,13 @@ class FontDisplay extends Audit {
const fontFaceDeclarations = newlinesStripped.match(/@font-face\s*{(.*?)}/g) || [];
// Go through all the @font-face declarations to find a declared `font-display: ` property
for (const declaration of fontFaceDeclarations) {
const rawFontDisplay = declaration.match(/font-display:(.*?);/);
// Find the font-display value by matching a single token, optionally surrounded by whitespace,
// followed either by a semicolon or the end of a block.
const rawFontDisplay = declaration.match(/font-display\s*:(\s*\w+\s*)(;|\})/);
// If they didn't have a font-display property, it's the default, and it's failing; bail
if (!rawFontDisplay) continue;
// If they don't have one of the passing font-display values, it's failing; bail
const hasPassingFontDisplay = PASSING_FONT_DISPLAY_REGEX.test(rawFontDisplay[0]);
const hasPassingFontDisplay = PASSING_FONT_DISPLAY_REGEX.test(rawFontDisplay[1].trim());
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nit: worth keeping the whitespace in the capture group if only going to trim it?

if (!hasPassingFontDisplay) continue;

// If it's passing, we'll try to find the URL it's referencing.
Expand Down
56 changes: 45 additions & 11 deletions lighthouse-core/test/audits/font-display-test.js
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Expand Up @@ -37,11 +37,13 @@ describe('Performance: Font Display audit', () => {
}

@font-face {
font-display: 'optional'; // invalid quotes, should still fail for being invalid rule
/* try up a directory with ' */
src: url('../font-b.woff');
}

@font-face {
font-display: optional // missing a semi-colon, should still fail for being invalid block
/* try no path with no quotes ' */
src: url(font.woff);
}
Expand Down Expand Up @@ -72,32 +74,32 @@ describe('Performance: Font Display audit', () => {
{url: networkRecords[2].url, wastedMs: 1000},
];
assert.strictEqual(result.rawValue, false);
assert.deepEqual(result.details.items, items);
expect(result.details.items).toEqual(items);
});

it('resolves URLs relative to stylesheet URL when available', async () => {
stylesheet.header.sourceURL = 'https://cdn.example.com/foo/bar/file.css';
stylesheet.content = `
@font-face {
font-display: 'block';
font-display: block;
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ha, whoops

/* try with " and same directory */
src: url("./font-a.woff");
}

@font-face {
font-display: 'block';
font-display: block;
/* try with " and site origin */
src: url("https://example.com/foo/bar/document-font.woff");
}

@font-face {
font-display: 'fallback';
font-display: fallback;
/* try up a directory with ' */
src: url('../font-b.woff');
}

@font-face {
font-display: 'optional';
font-display: optional;
/* try no path with no quotes ' */
src: url(font.woff);
}
Expand Down Expand Up @@ -128,25 +130,25 @@ describe('Performance: Font Display audit', () => {

const result = await FontDisplayAudit.audit(getArtifacts(), context);
assert.strictEqual(result.rawValue, true);
assert.deepEqual(result.details.items, []);
expect(result.details.items).toEqual([]);
});

it('passes when all fonts have a correct font-display rule', async () => {
stylesheet.content = `
@font-face {
font-display: 'block';
font-display: block;
/* try with " */
src: url("./font-a.woff");
}

@font-face {
font-display: 'fallback';
font-display: fallback;
/* try up a directory with ' */
src: url('../font-b.woff');
}

@font-face {
font-display: 'optional';
font-display: optional;
/* try no path with no quotes ' */
src: url(font.woff);
}
Expand All @@ -172,7 +174,7 @@ describe('Performance: Font Display audit', () => {

const result = await FontDisplayAudit.audit(getArtifacts(), context);
assert.strictEqual(result.rawValue, true);
assert.deepEqual(result.details.items, []);
expect(result.details.items).toEqual([]);
});

it('should handle real-world font-face declarations', async () => {
Expand Down Expand Up @@ -212,12 +214,44 @@ describe('Performance: Font Display audit', () => {

const result = await FontDisplayAudit.audit(getArtifacts(), context);
assert.strictEqual(result.rawValue, false);
assert.deepEqual(result.details.items.map(item => item.url), [
expect(result.details.items.map(item => item.url)).toEqual([
'https://edition.i.cdn.cnn.com/.a/fonts/cnn/3.7.2/cnnclock-black.woff2',
'https://registry.api.cnn.io/assets/fave/fonts/2.0.15/cnnsans-bold.woff',
// FontAwesome should pass
// 'https://example.com/foo/fonts/fontawesome-webfont.woff2?v=4.6.1',
'https://fonts.gstatic.com/s/lato/v14/S6u9w4BMUTPHh50XSwiPGQ3q5d0.woff2',
]);
});

it('handles varied font-display declarations', async () => {
stylesheet.content = `
@font-face {
src: url(font-0.woff);
font-display: swap
}

@font-face {src: url(font-1.woff);font-display : fallback
}

@font-face {
src: url(font-2.woff);
font-display:optional}

@font-face {
src: url(font-3.woff);
font-display : swap ; }

@font-face {src: url(font-4.woff);font-display:swap;}
`;

networkRecords = Array.from({length: 5}).map((_, idx) => ({
url: `https://example.com/foo/bar/font-${idx}.woff`,
endTime: 2, startTime: 1,
resourceType: 'Font',
}));

const result = await FontDisplayAudit.audit(getArtifacts(), context);
expect(result.details.items).toEqual([]);
assert.strictEqual(result.rawValue, true);
});
});