Accept basePath option.

index.js

@@ -43,7 +43,12 @@ function codeImport(options = {}) {
         ? parseInt(res.groups.from, 10)
         : undefined;
       const toLine = res.groups.to ? parseInt(res.groups.to, 10) : undefined;
-      const fileAbsPath = path.resolve(file.dirname, filePath);
+
+      if (!options.basePath && !file.dirname) {
+        throw new Error("Unable to parse base file path. Please configure options.basePath or modify your tooling to include path data, like mdxOptions.filepath.")
+      }
+
+      const fileAbsPath = path.resolve(options.basePath || file.dirname, filePath);
 
       if (options.async) {
         promises.push(

test.js

@@ -1,12 +1,24 @@
 const codeImport = require('./');
 const remark = require('remark');
 const path = require('path');
+const os = require('os');
 
 const input = q => `
 \`\`\`js file=./__fixtures__/say-#-hi.js${q}
 \`\`\`
 `;
 
+const basePathTestPath = path.resolve(process.cwd(), 'gatsby');
+const basePathTestInput = q => `
+\`\`\`js file=../__fixtures__/say-#-hi.js${q}
+\`\`\`
+`;
+
+const absolutePathTestInput = q => `
+\`\`\`js file=${path.normalize(process.cwd())}/__fixtures__/say-#-hi.js${q}
+\`\`\`
+`;
+
 test('Basic file import', () => {
   expect(
     remark()
@@ -27,6 +39,60 @@ test('Basic file import', () => {
   `);
 });
 
+test('Absolute file import', () => {
+  expect(
+    remark()
+      .use(codeImport, {})
+      .processSync({
+        contents: absolutePathTestInput(''),
+        path: path.resolve('test.md'),
+      })
+      .toString()
+  ).toBe(`\`\`\`js file=${path.normalize(process.cwd())}/__fixtures__/say-#-hi.js
+console.log('Hello remark-code-import!');${os.EOL}console.log('This is another line...');${os.EOL}console.log('This is the last line');${os.EOL}console.log('Oops, here is another');
+\`\`\`
+`);
+});
+
+test('Basic file import with basePath', () => {
+  expect(
+    remark()
+      .use(codeImport, {
+        basePath: basePathTestPath,
+      })
+      .processSync({
+        contents: basePathTestInput(''),
+        path: path.resolve('test.md'),
+      })
+      .toString()
+  ).toMatchInlineSnapshot(`
+    "\`\`\`js file=../__fixtures__/say-#-hi.js
+    console.log('Hello remark-code-import!');
+    console.log('This is another line...');
+    console.log('This is the last line');
+    console.log('Oops, here is another');
+    \`\`\`
+    "
+  `);
+});
+
+test('Absolute file import with basePath', () => {
+  expect(
+    remark()
+      .use(codeImport, {
+        basePath: basePathTestPath,
+      })
+      .processSync({
+        contents: absolutePathTestInput(''),
+        path: path.resolve('test.md'),
+      })
+      .toString()
+  ).toBe(`\`\`\`js file=${path.normalize(process.cwd())}/__fixtures__/say-#-hi.js
+console.log('Hello remark-code-import!');${os.EOL}console.log('This is another line...');${os.EOL}console.log('This is the last line');${os.EOL}console.log('Oops, here is another');
+\`\`\`
+`);
+});
+
 test('File import using line numbers', () => {
   expect(
     remark()