refactor system fonts to be generic exclusions list

src/BeaconPreloadFonts.js

@@ -9,19 +9,47 @@ class BeaconPreloadFonts {
     static FONT_FILE_REGEX = /\.(woff2?|ttf|otf|eot)(\?.*)?$/i;
 
     /**
-     * Checks if a given font family is a system font.
+     * Checks if a font family or URL should be excluded from preloading.
      * 
-     * This method checks if the provided font family is part of the system fonts
-     * defined in the configuration. It returns true if the font family is a system
-     * font, and false otherwise.
+     * This method determines if the provided font family or any of its URLs
+     * match any exclusion patterns defined in the configuration. It checks for
+     * exact matches and substring matches for both the font family and URLs.
      * 
      * @param {string} fontFamily - The font family to check.
-     * @returns {boolean} True if the font family is a system font, false otherwise.
+     * @param {string[]} urls - Array of font file URLs to check.
+     * @returns {boolean} True if the font should be excluded, false otherwise.
      */
-    isSystemFont(fontFamily) {
-        const systemFonts = new Set(this.config.system_fonts);
-        return systemFonts.has(fontFamily);
-    }
+    isExcluded(fontFamily, urls) {
+        const exclusions = this.config.preload_fonts_exclusions;
+        const exclusionsSet = new Set(exclusions);
+
+        // First check for exact match of fontFamily.
+        if (exclusionsSet.has(fontFamily)) {
+          return true;
+        }
+
+        // Then check if any exclusion is a substring of fontFamily.
+        if (exclusions.some(exclusion => fontFamily.includes(exclusion))) {
+          return true;
+        }
+
+        // Check URLs.
+        if (Array.isArray(urls) && urls.length > 0) {
+          // First check for exact matches of any URL.
+          if (urls.some(url => exclusionsSet.has(url))) {
+            return true;
+          }
+
+          // Then check if any exclusion is a substring of any URL.
+          if (urls.some(url => 
+            exclusions.some(exclusion => url.includes(exclusion))
+          )) {
+            return true;
+          }
+        }
+
+        return false;
+      }
 
     /**
      * Checks if an element is visible in the viewport.
@@ -188,11 +216,12 @@ class BeaconPreloadFonts {
                     style.content !== 'none' && style.content !== '""' :
                     element.textContent.trim();
 
-                if (hasContent && !this.isSystemFont(fontFamily) && stylesheetFonts[fontFamily]) {
-                    if (!hostedFonts.has(fontFamily)) {
+                if (hasContent && stylesheetFonts[fontFamily]) {
+                    let urls = stylesheetFonts[fontFamily].urls;
+                    if (!this.isExcluded(fontFamily, urls) && !hostedFonts.has(fontFamily)) {
                         hostedFonts.set(fontFamily, {
                             elements: new Set(),
-                            urls: stylesheetFonts[fontFamily].urls,
+                            urls: urls,
                             variations: stylesheetFonts[fontFamily].variations
                         });
                     }
@@ -447,7 +476,7 @@ class BeaconPreloadFonts {
                 const style = window.getComputedStyle(element);
                 const fontInfo = getFontInfoForElement(style);
                 if (fontInfo) {
-                    if (!matches.has(fontInfo.url)) {
+                    if (!this.isExcluded(fontInfo.family, [fontInfo.url]) && !matches.has(fontInfo.url)) {
                         matches.set(fontInfo.url, {
                             elements: new Set(),
                             variations: new Set()
@@ -467,7 +496,7 @@ class BeaconPreloadFonts {
                 if (pseudoStyle.content !== 'none' && pseudoStyle.content !== '""') {
                     const fontInfo = getFontInfoForElement(pseudoStyle);
                     if (fontInfo) {
-                        if (!matches.has(fontInfo.url)) {
+                        if (!this.isExcluded(fontInfo.family, [fontInfo.url]) && !matches.has(fontInfo.url)) {
                             matches.set(fontInfo.url, {
                                 elements: new Set(),
                                 variations: new Set()

test/BeaconPreloadFonts.test.js

@@ -33,7 +33,8 @@ describe('BeaconPreloadFonts', () => {
         };
         const config = {
             system_fonts: ['Arial', 'Helvetica'],
-            font_data: {}
+            font_data: {},
+            preload_fonts_exclusions: []
         };
 
         // Initialize the class with mock config and logger
@@ -103,13 +104,30 @@ describe('BeaconPreloadFonts', () => {
         sinon.restore(); // Restore sinon mocks
     });
 
-    describe('isSystemFont', () => {
-        it('should return true for system fonts', () => {
-            assert.strictEqual(beaconPreloadFonts.isSystemFont('Arial'), true);
+    describe('isExcluded', () => {
+        it('should return true when fontFamily exactly matches exclusion', () => {
+            beaconPreloadFonts.config.preload_fonts_exclusions = ['Arial'];
+            assert.strictEqual(beaconPreloadFonts.isExcluded('Arial', []), true);
         });
-
-        it('should return false for non-system fonts', () => {
-            assert.strictEqual(beaconPreloadFonts.isSystemFont('Times New Roman'), false);
+
+        it('should return true when fontFamily contains exclusion substring', () => {
+            beaconPreloadFonts.config.preload_fonts_exclusions = ['Ari'];
+            assert.strictEqual(beaconPreloadFonts.isExcluded('Arial', []), true);
+        });
+
+        it('should return true when URL exactly matches exclusion', () => {
+            beaconPreloadFonts.config.preload_fonts_exclusions = ['https://example.com/font.woff2'];
+            assert.strictEqual(beaconPreloadFonts.isExcluded('CustomFont', ['https://example.com/font.woff2']), true);
+        });
+
+        it('should return true when URL contains exclusion substring', () => {
+            beaconPreloadFonts.config.preload_fonts_exclusions = ['example.com'];
+            assert.strictEqual(beaconPreloadFonts.isExcluded('CustomFont', ['https://example.com/font.woff2']), true);
+        });
+
+        it('should return false when neither fontFamily nor URLs match exclusions', () => {
+            beaconPreloadFonts.config.preload_fonts_exclusions = ['Roboto', 'fonts.gstatic.com'];
+            assert.strictEqual(beaconPreloadFonts.isExcluded('OpenSans', ['https://example.com/font.woff2']), false);
         });
     });