Add utility for stripping local(...) tokens from a @font-face src pro…

…perty

lib/util/fonts/stripLocalTokens.js

@@ -0,0 +1,51 @@
+const postcssValuesParser = require('postcss-values-parser');
+
+module.exports = function stripLocalTokens(cssValue) {
+  const tokens = postcssValuesParser(cssValue).tokens;
+  for (let i = 0; i < tokens.length - 3; i += 1) {
+    if (
+      tokens[i][0] === 'word' &&
+      tokens[i][1].toLowerCase() === 'local' &&
+      tokens[i + 1][0] === '(' &&
+      (tokens[i + 2][0] === 'string' || tokens[i + 2][0] === 'word') &&
+      tokens[i + 3][0] === ')'
+    ) {
+      let startIndex = i;
+      let numTokensToRemove = 4;
+      let commaBefore = false;
+      let commaAfter = false;
+      while (
+        startIndex > 0 &&
+        ['space', 'comma'].includes(tokens[startIndex - 1][0])
+      ) {
+        if (tokens[startIndex - 1][0] === 'comma') {
+          commaBefore = true;
+        }
+        startIndex -= 1;
+        numTokensToRemove += 1;
+      }
+
+      while (
+        startIndex + numTokensToRemove < tokens.length &&
+        ['space', 'comma'].includes(tokens[startIndex + numTokensToRemove][0])
+      ) {
+        if (tokens[startIndex + numTokensToRemove][0] === 'comma') {
+          commaAfter = true;
+        }
+        numTokensToRemove += 1;
+      }
+      if (commaBefore && commaAfter) {
+        tokens.splice(
+          startIndex,
+          numTokensToRemove,
+          ['comma', ','],
+          ['space', ' ']
+        );
+      } else {
+        tokens.splice(startIndex, numTokensToRemove);
+      }
+      i = startIndex - 1;
+    }
+  }
+  return tokens.map(token => token[1]).join('');
+};

test/util/fonts/stripLocalTokens.js

@@ -0,0 +1,83 @@
+const expect = require('unexpected').clone();
+const stripLocalTokens = require('../../../lib/util/fonts/stripLocalTokens');
+
+expect.addAssertion(
+  '<string> to come out as <string>',
+  (expect, subject, value) => {
+    expect(stripLocalTokens(subject), 'to equal', value);
+  }
+);
+
+describe('stripLocalTokens', function() {
+  it('should strip a standalone local(...) token', function() {
+    expect('local(foo)', 'to come out as', '');
+  });
+
+  it('should strip an initial local(...) token and a following comma', function() {
+    expect('local(foo), url(bar)', 'to come out as', 'url(bar)');
+  });
+
+  it('should strip a local(...) token surrounded by multple other tokens and leave a comma', function() {
+    expect(
+      'url(foo), local(bar), url(quux)',
+      'to come out as',
+      'url(foo), url(quux)'
+    );
+  });
+
+  it('should ignore the casing of the word local', function() {
+    expect(
+      'url(foo), LOCAL(bar), url(quux)',
+      'to come out as',
+      'url(foo), url(quux)'
+    );
+  });
+
+  it('should support singlequoted strings', function() {
+    expect(
+      `url('foo'), local('bar'), url('quux')`,
+      'to come out as',
+      "url('foo'), url('quux')"
+    );
+  });
+
+  it('should support doublequoted strings', function() {
+    expect(
+      `url("foo"), local("bar"), url("quux")`,
+      'to come out as',
+      'url("foo"), url("quux")'
+    );
+  });
+
+  it('should strip multiple consecutive local(...) tokens with space between them', function() {
+    expect(
+      `url('foo'), local(bar), local(quux), url('baz')`,
+      'to come out as',
+      "url('foo'), url('baz')"
+    );
+  });
+
+  it('should strip multiple consecutive local(...) tokens with space before and after the comma', function() {
+    expect(
+      `url('foo') , local(bar) , local(quux) , url('baz')`,
+      'to come out as',
+      "url('foo'), url('baz')"
+    );
+  });
+
+  it('should strip multiple initial, consecutive local(...) tokens', function() {
+    expect(
+      `local('Roboto Bold Italic'), local('Roboto-BoldItalic'), url(KFOjCnqEu92Fr1Mu51TzBic6CsI.woff) format('woff')`,
+      'to come out as',
+      `url(KFOjCnqEu92Fr1Mu51TzBic6CsI.woff) format('woff')`
+    );
+  });
+
+  it('should strip multiple consecutive local(...) tokens without space between them', function() {
+    expect(
+      `url('foo'), local(bar),local(quux), url('baz')`,
+      'to come out as',
+      "url('foo'), url('baz')"
+    );
+  });
+});