gatsby-node.js

const path = require('path');

exports.createPages = ({ graphql, actions }) => {
    const { createPage } = actions;

    const DYNAMIC_PAGES_QUERY = `
        query ContentPagesQuery {
            global: contentfulGlobalSiteSettings {
                currentYear: conferenceStartDateTime(formatString: "YYYY")
                currentConferenceStartDate: conferenceStartDateTime(formatString: "YYYY-MM-DD")
                currentConferenceEndDate: conferenceEndDateTime(formatString: "YYYY-MM-DD")
            }
            contentPages: allContentfulContentPageLayout {
                edges {
                    node {
                        page {
                            slug
                        }
                    }
                }
            }
            sessionPages: allContentfulSessionsPageLayout {
                edges {
                    node {
                        conferenceDate
                        conferenceYear: conferenceDate(formatString: "YYYY")
                        page {
                            slug
                        }
                    }
                }
            }
        }`;

    return new Promise((resolve) => {
        graphql(DYNAMIC_PAGES_QUERY)
            .then(({ data }) => {
                const { currentYear, currentConferenceStartDate, currentConferenceEndDate } = data.global;

                const currentConferenceStartOfDay = new Date(currentConferenceStartDate);
                currentConferenceStartOfDay.setUTCHours(0, 0, 0, 0);

                const currentConferenceEndOfDay = new Date(currentConferenceEndDate);
                currentConferenceEndOfDay.setUTCHours(23, 59, 59, 999);

                // Create Content Pages: Dynamically created pages from Contentful Entries
                data.contentPages.edges.forEach(({node}) => {
                    createPage({
                        path: `/${ node.page.slug }`,
                        component: path.resolve('./src/templates/contentPageLayout.tsx'),
                        context: {
                            slug: node.page.slug
                        }
                    })
                });

                // Create Session Pages: A page that shows all the sessions from each conference year
                data.sessionPages.edges.forEach(({node}) => {
                    const conferenceStartOfDay = new Date(node.conferenceDate);
                    conferenceStartOfDay.setUTCHours(0, 0, 0, 0);

                    const conferenceEndOfDay = new Date(node.conferenceDate);
                    conferenceEndOfDay.setUTCHours(23, 59, 59, 999);

                    createPage({
                        path: `/${ node.page.slug }`,
                        component: path.resolve('./src/templates/sessionsPageLayout.tsx'),
                        context: {
                            conferenceStartOfDay: conferenceStartOfDay.toISOString(),
                            conferenceEndOfDay: conferenceEndOfDay.toISOString(),
                            slug: node.page.slug,
                            isActive: node.conferenceYear === currentYear
                        }
                    })
                });

                createPage({
                    path: `/`,
                    component: path.resolve('./src/templates/index.tsx'),
                    context: {
                        currentConferenceStartOfDay: currentConferenceStartOfDay.toISOString(),
                        currentConferenceEndOfDay: currentConferenceEndOfDay.toISOString()
                    }
                })

                resolve();
            });
    });
};

// https://github.com/gatsbyjs/gatsby/issues/8612#issuecomment-428820523
exports.onCreateWebpackConfig = ({ actions, stage }) => {
    if (stage === "build-html") {
        actions.setWebpackConfig({
            module: {
                rules: [
                    {
                        test: /firebase/,
                        use: ['null-loader']
                    },
                ],
            }
        })
    }

    if (stage === 'develop') {
        actions.setWebpackConfig({
            devtool: 'cheap-module-source-map'
        });
    }
};