Error when adding siteMetaData. it won't run

[a-ditucalan]

Description

When I tried to add siteMetaData in config file and start running it. it shows Error: Reducers may not dispatch actions. this is new project using gatsby-starter-hello-world-template

Steps to reproduce

module.exports = {
siteMetaData:{
title: 'Fullstack bootcamp'
},
plugins:[
'gatsby-plugin-sass',
],
}

Expected result

it should run the script gatsby develop

Actual result

it return error when I start running gatsby develop

Environment

System:
OS: macOS Mojave 10.14.6
CPU: (8) x64 Intel(R) Core(TM) i5-8259U CPU @ 2.30GHz
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 12.16.0 - /usr/local/opt/node@12/bin/node
Yarn: 1.19.1 - /usr/local/bin/yarn
npm: 6.13.4 - /usr/local/opt/node@12/bin/npm
Languages:
Python: 2.7.16 - /usr/bin/python
Browsers:
Chrome: 80.0.3987.149
Safari: 13.1
npmPackages:
gatsby: ^2.19.45 => 2.20.12
gatsby-plugin-sass: ^2.2.1 => 2.2.1
npmGlobalPackages:
gatsby-cli: 2.11.4

[Js-Brecht]

Hello @a-ditucalan. Can you share a minimal reproduction of the issue? It would help a great deal to track down the problem.

[Js-Brecht]

Hey @a-ditucalan, I just noticed something: Data in siteMetaData shouldn't be capitalized.

If I make my gatsby-config look like that, I get the same error you do. I can't be 100% sure that's what's causing the issue, but at the very least, you won't be able to use that value in your project with it like it is.

[github-actions]

Hiya!

This issue has gone quiet. Spooky quiet. 👻

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[pieh]

Seems like we have fairly similar report in #23468 and we do have reproduction there (linked issue is bit more complex than just unhelpful error message)