Use postcss value parser to find variables

package.json

@@ -54,6 +54,7 @@
     "another-json": "^0.2.0",
     "base64-arraybuffer": "^0.2.0",
     "dompurify": "^2.3.0",
-    "off-color": "^2.0.0"
+    "off-color": "^2.0.0",
+    "postcss-value-parser": "^4.2.0"
   }
 }

postcss/css-compile-variables.js

@@ -1,4 +1,5 @@
 const offColor = require("off-color").offColor;
+const valueParser = require("postcss-value-parser");
 
 let aliasMap;
 let resolvedMap;
@@ -9,28 +10,45 @@ function getValueFromAlias(alias) {
     return resolvedMap.get(derivedVariable); // what if we haven't resolved this variable yet?
 }
 
-function resolveDerivedVariable(decl, variables) {
-    const matches = decl.value.match(RE_VARIABLE_VALUE);
-    if (matches) {
-        const [, wholeVariable, baseVariable, operation, argument] = matches;
-        if (!variables[baseVariable]) {
-            // hmm.. baseVariable should be in config..., maybe this is an alias?
-            if (!aliasMap.get(`--${baseVariable}`)) {
-                throw new Error(`Cannot derive from ${baseVariable} because it is neither defined in config nor is it an alias!`);
-            }
+function parseDeclarationValue(value) {
+    const parsed = valueParser(value);
+    const variables = [];
+    parsed.walk(node => {
+        if (node.type !== "function" && node.value !== "var") {
+            return;
         }
-        switch (operation) {
-            case "darker": {
-                const colorString = variables[baseVariable] ?? getValueFromAlias(baseVariable);
-                const newColorString = offColor(colorString).darken(argument / 100).hex();
-                resolvedMap.set(wholeVariable, newColorString);
-                break;
+        const variable = node.nodes[0];
+        variables.push(variable.value);
+    });
+    return variables;
+}
+
+function resolveDerivedVariable(decl, variables) {
+    const RE_VARIABLE_VALUE = /--(.+)--(.+)-(.+)/;
+    const variableCollection = parseDeclarationValue(decl.value);
+    for (const variable of variableCollection) {
+        const matches = variable.match(RE_VARIABLE_VALUE);
+        if (matches) {
+            const [wholeVariable, baseVariable, operation, argument] = matches;
+            if (!variables[baseVariable]) {
+                // hmm.. baseVariable should be in config..., maybe this is an alias?
+                if (!aliasMap.get(`--${baseVariable}`)) {
+                    throw new Error(`Cannot derive from ${baseVariable} because it is neither defined in config nor is it an alias!`);
+                }
             }
-            case "lighter": {
-                const colorString = variables[baseVariable] ?? getValueFromAlias(baseVariable);
-                const newColorString = offColor(colorString).lighten(argument / 100).hex();
-                resolvedMap.set(wholeVariable, newColorString);
-                break;
+            switch (operation) {
+                case "darker": {
+                    const colorString = variables[baseVariable] ?? getValueFromAlias(baseVariable);
+                    const newColorString = offColor(colorString).darken(argument / 100).hex();
+                    resolvedMap.set(wholeVariable, newColorString);
+                    break;
+                }
+                case "lighter": {
+                    const colorString = variables[baseVariable] ?? getValueFromAlias(baseVariable);
+                    const newColorString = offColor(colorString).lighten(argument / 100).hex();
+                    resolvedMap.set(wholeVariable, newColorString);
+                    break;
+                }
             }
         }
     }

postcss/test.js

@@ -61,6 +61,29 @@ module.exports.tests = function tests() {
                 color: var(--icon-color--darker-20);
             }`;
             assert.rejects(async () => await postcss([plugin({ variables: {} })]).process(css, { from: undefined, }));
+        },
+
+        "multiple derived variable in single declaration is parsed correctly": async (assert) => {
+            const inputCSS = `div {
+                background-color: linear-gradient(var(--foo-color--lighter-50), var(--foo-color--darker-20));
+            }`;
+            const transformedColor1 = offColor("#ff0").lighten(0.5);
+            const transformedColor2 = offColor("#ff0").darken(0.2);
+            const outputCSS =
+                inputCSS +
+                `
+            :root {
+                --foo-color: #ff0;
+                --foo-color--lighter-50: ${transformedColor1.hex()};
+                --foo-color--darker-20: ${transformedColor2.hex()};
+            }
+            `;
+            await run(
+                inputCSS,
+                outputCSS,
+                { variables: { "foo-color": "#ff0" } },
+                assert
+            );
         }
     };
 };

yarn.lock

@@ -1222,6 +1222,11 @@ postcss-flexbugs-fixes@^5.0.2:
   resolved "https://registry.yarnpkg.com/postcss-flexbugs-fixes/-/postcss-flexbugs-fixes-5.0.2.tgz#2028e145313074fc9abe276cb7ca14e5401eb49d"
   integrity sha512-18f9voByak7bTktR2QgDveglpn9DTbBWPUzSOe9g0N4WR/2eSt6Vrcbf0hmspvMI6YWGywz6B9f7jzpFNJJgnQ==
 
+postcss-value-parser@^4.2.0:
+  version "4.2.0"
+  resolved "https://registry.yarnpkg.com/postcss-value-parser/-/postcss-value-parser-4.2.0.tgz#723c09920836ba6d3e5af019f92bc0971c02e514"
+  integrity sha512-1NNCs6uurfkVbeXG4S8JFT9t19m45ICnif8zWLd5oPSZ50QnwMfK+H3jv408d4jw/7Bttv5axS5IiHoLaVNHeQ==
+
 postcss@^8.3.8:
   version "8.3.9"
   resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.3.9.tgz#98754caa06c4ee9eb59cc48bd073bb6bd3437c31"