feat(extract): allow existing custom defined functions

src/extract.js

@@ -41,9 +41,11 @@ function makeExtractionCompileOptions(compileOptions, entryFilename, extractions
     Object.assign(extractionFunctions, extractions[extractionKey].injectedFunctions);
   });
 
-  extractionCompileOptions.functions = extractionFunctions;
+  extractionCompileOptions.functions = Object.assign(extractionFunctions, compileOptions.functions);
   extractionCompileOptions.data = extractions[entryFilename].injectedData;
-  extractionCompileOptions.importer = importer;
+  if(!makeExtractionCompileOptions.imported) {
+    extractionCompileOptions.importer = importer;
+  }
 
   return extractionCompileOptions;
 }

test/functions.js

@@ -0,0 +1,56 @@
+const { expect } = require('chai');
+const path = require('path');
+const { render, renderSync } = require('../lib');
+const { normalizePath } = require('../lib/extract');
+const { types } = require('node-sass');
+
+const functionsFile = path.join(__dirname, 'sass', 'functions.scss');
+
+function verifyFunctions(rendered, sourceFile) {
+  expect(rendered.vars).to.exist;
+  expect(rendered.vars).to.have.property('global');
+  expect(rendered.vars.global).to.have.property('$fColor');
+  expect(rendered.vars.global).to.have.property('$fSize');
+
+  expect(rendered.vars.global.$fColor.value.r).to.equal(0);
+  expect(rendered.vars.global.$fColor.value.g).to.equal(255);
+  expect(rendered.vars.global.$fColor.value.b).to.equal(0);
+  expect(rendered.vars.global.$fColor.value.a).to.equal(1);
+  expect(rendered.vars.global.$fColor.value.hex).to.equal('#00ff00');
+  expect(rendered.vars.global.$fColor.type).to.equal('SassColor');
+  expect(rendered.vars.global.$fColor.sources).to.have.length(1);
+  expect(rendered.vars.global.$fColor.sources[0]).to.equal(normalizePath(sourceFile));
+  expect(rendered.vars.global.$fColor.expressions).to.have.length(1);
+  expect(rendered.vars.global.$fColor.expressions[0]).to.equal('fn-color()');
+
+  expect(rendered.vars.global.$fSize.value).to.equal(20);
+  expect(rendered.vars.global.$fSize.unit).to.equal('px');
+  expect(rendered.vars.global.$fSize.type).to.equal('SassNumber');
+  expect(rendered.vars.global.$fSize.sources).to.have.length(1);
+  expect(rendered.vars.global.$fSize.sources[0]).to.equal(normalizePath(sourceFile));
+  expect(rendered.vars.global.$fSize.expressions).to.have.length(1);
+  expect(rendered.vars.global.$fSize.expressions[0]).to.equal('fn-size(2)');
+}
+
+const functions = {
+  'fn-color()': () => new types.Color(0, 255, 0),
+  'fn-size($multiplier)': (multiplier) => new types.Number(10 * multiplier.getValue(), 'px'),
+}
+
+describe('functions', () => {
+  describe('sync', () => {
+    it('should extract all variables', () => {
+      const rendered = renderSync({ file: functionsFile, functions });
+      verifyFunctions(rendered, functionsFile);
+    });
+  });
+
+  describe('async', () => {
+    it('should extract all variables', () => {
+      return render({ file: functionsFile, functions })
+      .then(rendered => {
+        verifyFunctions(rendered, functionsFile);
+      });
+    });
+  });
+});

test/sass/functions.scss

@@ -0,0 +1,2 @@
+$fColor: fn-color();
+$fSize: fn-size(2);