From cf31fa627551cbeaf33f7c8cc36801f003bd2f2d Mon Sep 17 00:00:00 2001
From: Dylan Staley <88163+dstaley@users.noreply.github.com>
Date: Tue, 1 Jul 2025 15:40:55 -0700
Subject: [PATCH] feat(clerk-js): Remove CSS variables when modern color isn't
 supported

---
 .../__tests__/parseVariables.spec.ts          | 58 +++++++++++++++++++
 .../src/ui/customizables/parseVariables.ts    | 46 ++++++++++++++-
 2 files changed, 103 insertions(+), 1 deletion(-)
 create mode 100644 packages/clerk-js/src/ui/customizables/__tests__/parseVariables.spec.ts

diff --git a/packages/clerk-js/src/ui/customizables/__tests__/parseVariables.spec.ts b/packages/clerk-js/src/ui/customizables/__tests__/parseVariables.spec.ts
new file mode 100644
index 00000000000..d72ba57e2de
--- /dev/null
+++ b/packages/clerk-js/src/ui/customizables/__tests__/parseVariables.spec.ts
@@ -0,0 +1,58 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+// Mock cssSupports
+vi.mock('../../utils/cssSupports', () => ({
+  cssSupports: {
+    modernColor: vi.fn(),
+  },
+}));
+
+import { cssSupports } from '@/ui/utils/cssSupports';
+
+import { removeInvalidValues } from '../parseVariables';
+
+const mockModernColorSupport = vi.mocked(cssSupports.modernColor);
+
+describe('removeInvalidValues', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mockModernColorSupport.mockReturnValue(false);
+  });
+
+  it('should return the variables as-is if modern color support is present', () => {
+    mockModernColorSupport.mockReturnValue(true);
+    const variables = {
+      colorPrimary: 'var(--color-primary)',
+    };
+
+    const result = removeInvalidValues(variables);
+    expect(result).toEqual({ colorPrimary: 'var(--color-primary)' });
+  });
+
+  it('should remove invalid string values if modern color support is not present', () => {
+    mockModernColorSupport.mockReturnValue(false);
+    const variables = {
+      colorPrimary: 'var(--color-primary)',
+      colorDanger: '#ff0000',
+    };
+
+    const result = removeInvalidValues(variables);
+    expect(result).toEqual({ colorDanger: '#ff0000' });
+  });
+
+  it('should remove invalid object values if modern color support is not present', () => {
+    mockModernColorSupport.mockReturnValue(false);
+    const variables = {
+      colorPrimary: {
+        400: 'var(--color-primary-500)',
+        500: '#fff',
+      },
+      colorDanger: {
+        500: '#ff0000',
+      },
+    };
+
+    const result = removeInvalidValues(variables);
+    expect(result).toEqual({ colorDanger: { 500: '#ff0000' } });
+  });
+});
diff --git a/packages/clerk-js/src/ui/customizables/parseVariables.ts b/packages/clerk-js/src/ui/customizables/parseVariables.ts
index db660335073..fab13f448de 100644
--- a/packages/clerk-js/src/ui/customizables/parseVariables.ts
+++ b/packages/clerk-js/src/ui/customizables/parseVariables.ts
@@ -4,11 +4,12 @@ import { spaceScaleKeys } from '../foundations/sizes';
 import type { fontSizes, fontWeights } from '../foundations/typography';
 import { colors } from '../utils/colors';
 import { colorOptionToThemedAlphaScale, colorOptionToThemedLightnessScale } from '../utils/colors/scales';
+import { cssSupports } from '../utils/cssSupports';
 import { fromEntries } from '../utils/fromEntries';
 import { removeUndefinedProps } from '../utils/removeUndefinedProps';
 
 export const createColorScales = (theme: Theme) => {
-  const variables = theme.variables || {};
+  const variables = removeInvalidValues(theme.variables || {});
 
   const dangerScale = colorOptionToThemedLightnessScale(variables.colorDanger, 'danger');
   const primaryScale = colorOptionToThemedLightnessScale(variables.colorPrimary, 'primary');
@@ -43,6 +44,49 @@ export const createColorScales = (theme: Theme) => {
   });
 };
 
+export const removeInvalidValues = (variables: NonNullable<Theme['variables']>): NonNullable<Theme['variables']> => {
+  // Check for modern color support. If present, we can simply return the variables as-is since we support everything
+  // CSS supports.
+  if (cssSupports.modernColor()) {
+    return variables;
+  }
+
+  // If not, we need to remove any values that are specified with CSS variables, as our color scale generation only
+  // supports CSS variables using modern CSS functionality.
+  const validVariables: Theme['variables'] = Object.fromEntries(
+    Object.entries(variables).filter(([key, value]) => {
+      if (typeof value === 'string') {
+        const isValid = !value.startsWith('var(');
+        if (!isValid) {
+          console.warn(
+            `Invalid color value: ${value} for key: ${key}, using default value instead. Using CSS variables is not supported in this browser.`,
+          );
+        }
+        return isValid;
+      }
+
+      if (typeof value === 'object') {
+        return Object.entries(value).every(([key, value]) => {
+          if (typeof value !== 'string') return true;
+
+          const isValid = !value.startsWith('var(');
+          if (!isValid) {
+            console.warn(
+              `Invalid color value: ${value} for key: ${key}, using default value instead. Using CSS variables is not supported in this browser.`,
+            );
+          }
+
+          return isValid;
+        });
+      }
+
+      return false;
+    }),
+  );
+
+  return validVariables;
+};
+
 export const createRadiiUnits = (theme: Theme) => {
   const { borderRadius } = theme.variables || {};
   if (borderRadius === undefined) {