Added options.resolve function allowing resolveId override and options.paths will fallback to relative paths

README.md

@@ -53,10 +53,25 @@ See [PostCSS] docs for examples for your environment.
 
 #### options.paths
 
-Array of paths to resolve URL. Paths are tried in order, until an existing file is found.
+Array of paths to resolve URL. Array paths are tried in order, until an existing file is found or will fallback to using the relative path.
 
 Default: `false` - path will be relative to source file if it was specified.
 
+#### options.resolve
+
+Function to resolve URL. This option will override the default file id resolver that uses "paths" option.
+Function recieves `file`, `url`, and `opts` arguments and expects to return an absolute path as a `string`.
+
+For example
+
+```js
+function resolve(file, url, opts) {
+    return path.resolve('svg-folder', url);
+}
+```
+
+Default: `function` - internal resolver using "paths" option and relative path.
+
 #### options.removeFill
 
 Default: `false` - with `true` removes all `fill` attributes before applying specified.

lib/index.js

@@ -44,7 +44,10 @@ module.exports = postcss.plugin(
             const { name, url } = parseRuleDefinition(node.params);
             const { params, selectors } = getRuleParams(node);
             const loader = {
-              id: resolveId(file, url, opts),
+              id:
+                typeof opts.resolve === "function"
+                  ? opts.resolve(file, url, opts)
+                  : resolveId(file, url, opts),
               parent: file,
               params,
               selectors,
@@ -68,7 +71,10 @@ module.exports = postcss.plugin(
             statements.loaders.forEach(
               ({ url, params, valueNode, parsedValue }) => {
                 const loader = {
-                  id: resolveId(file, url, opts),
+                  id:
+                    typeof opts.resolve === "function"
+                      ? opts.resolve(file, url, opts)
+                      : resolveId(file, url, opts),
                   parent: file,
                   params,
                   selectors: {},

lib/resolveId.js

@@ -12,8 +12,6 @@ module.exports = function resolveId(file, url, opts) {
         return absolutePath;
       }
     }
-
-    return absolutePath;
   }
 
   if (file) {

test/options.test.js

@@ -1,4 +1,5 @@
 /* eslint-env mocha */
+const { resolve } = require("path");
 const { compare } = require("./utils.js");
 
 process.chdir(__dirname);
@@ -71,6 +72,44 @@ test('should prefer "paths" option over "from"', () => {
   );
 });
 
+test('should fallback to relative option if "paths" option can\'t be resolved', () => {
+  return compare(
+    `
+    @svg-load icon url(fixtures/basic.svg) {}
+    background: svg-load('fixtures/basic.svg');
+    background: svg-inline(icon);
+    `,
+    `
+    background: url("data:image/svg+xml;charset=utf-8,<svg xmlns=\'http://www.w3.org/2000/svg\' id='basic'/>");
+    background: url("data:image/svg+xml;charset=utf-8,<svg xmlns=\'http://www.w3.org/2000/svg\' id='basic'/>");
+    `,
+    {
+      from: "input.css",
+      paths: ["./does_not_exist"],
+      encode: false
+    }
+  );
+});
+
+test('should resolve file path using the "resolve" option function', () => {
+  return compare(
+    `
+    @svg-load icon url(basic.svg) {}
+    background: svg-load('basic.svg');
+    background: svg-inline(icon);
+    `,
+    `
+    background: url("data:image/svg+xml;charset=utf-8,<svg xmlns=\'http://www.w3.org/2000/svg\' id='basic'/>");
+    background: url("data:image/svg+xml;charset=utf-8,<svg xmlns=\'http://www.w3.org/2000/svg\' id='basic'/>");
+    `,
+    {
+      from: "input.css",
+      resolve: (file, url, opts) => resolve("fixtures", url),
+      encode: false
+    }
+  );
+});
+
 test("should ignore xmlns absence", () => {
   return compare(
     `background: svg-load('fixtures/basic.svg');`,