[gatsby-plugin-google-analytics] trackingId is required in development after upgrading to 3.0.0

Description

Using gatsby-plugin-google-analytics, it is noted in the docs that:

Note that this plugin is disabled while running gatsby develop. This way, actions are not tracked while you are still developing your project. Once you run gatsby build the plugin is enabled. Test it with gatsby serve.

Personally I keep my GA tracking id in netlify environment variable so it’s only available at build time. After upgrading to version 3.0.0 I get the following error message in development

ERROR #11331 PLUGIN

Invalid plugin options for “gatsby-plugin-google-analytics”:

• “trackingId” is required

Steps to reproduce

• Install gatsby-plugin-google-analytics version 3.0.0
• Start development process with npm start

Expected result

The plugin should allow empty / undefined trackingId in development.

Actual result

Error is thrown and development process is stopped.

Environment

System: OS: Windows 10 10.0.19042 CPU: (8) x64 Intel® Core™ i7-8550U CPU @ 1.80GHz Binaries: Node: 14.15.1 - C:\Program Files\nodejs\node.EXE npm: 6.14.8 - C:\Program Files\nodejs\npm.CMD Browsers: Edge: Spartan (44.19041.423.0), Chromium (88.0.705.81) npmPackages: gatsby: ^3.0.0 => 3.0.0 gatsby-plugin-google-analytics: ^3.0.0 => 3.0.0 gatsby-plugin-image: ^1.0.0 => 1.0.0 gatsby-plugin-manifest: ^3.0.0 => 3.0.0 gatsby-plugin-mdx: ^2.0.0 => 2.0.0 gatsby-plugin-netlify: ^3.0.0 => 3.0.0 gatsby-plugin-offline: ^4.0.0 => 4.0.0 gatsby-plugin-react-helmet: ^4.0.0 => 4.0.0 gatsby-plugin-robots-txt: ^1.5.5 => 1.5.5 gatsby-plugin-sharp: ^3.0.0 => 3.0.0 gatsby-plugin-sitemap: ^3.0.0 => 3.0.0 gatsby-plugin-styled-components: ^4.0.0 => 4.0.0 gatsby-remark-autolink-headers: ^3.0.0 => 3.0.0 gatsby-remark-copy-linked-files: ^3.0.0 => 3.0.0 gatsby-remark-embedder: ^4.1.0 => 4.1.0 gatsby-remark-images: ^4.0.0 => 4.0.0 gatsby-remark-prismjs: ^4.0.0 => 4.0.0 gatsby-source-filesystem: ^3.0.0 => 3.0.0 gatsby-transformer-sharp: ^3.0.0 => 3.0.0

I would like to submit a PR if needed (with maybe a little help of getting around) 🚀

[wardpeet]

You can use this pattern

const dynamicPlugins = [];
if (process.env.GA) {
  dynamicPlugins.push({
    resolve: 'gatsby-plugin-analytics',
    options: {
      trackingId: process.env.GA
    }
  })
}

module.exports = {
  // config
  plugins: [
    ...dynamicPlugins
  ]
}

[vladar]

I think this was intentional for the major bump: https://github.com/gatsbyjs/gatsby/pull/29413/files#diff-618b4bd7e0c4df7c7818d36a3f92517c9ceb898b635b72da933dc09ab7d4b9f8

But I don’t have enough context on it. CC @wardpeet @laurieontech