Gatsby-plugin-sitemap generates NaN-NaN-NaN on <lastmod>

[flikteoh]

Description

When using gatsby-plugin-sitemap to generate sitemap.xml, <lastmod> was not available by default.

Manually adding this would output <lastmod> tags in the final sitemap.xml, but the date were written as NaN-NaN-NaN

Note: Even if we manually uses lastmod: '2020-08-03T01:54:49.000Z' during the serialize below still outputs as NaN

Steps to reproduce

{
      resolve: `gatsby-plugin-sitemap`,
      options: {
        createLinkInHead: true,
        query: `{
          site {
            siteMetadata {
              siteUrl
            }
          }

          allSitePage {
            nodes {
              path
              context {
                updated
              }
            }
          }
        }`,
        resolveSiteUrl: ({ site }) => {
          return site.siteMetadata.siteUrl;
        },
        serialize: ({ site, allSitePage }) =>
          allSitePage.nodes.map((node) => {
            return {
              url: `${site.siteMetadata.siteUrl}${node.path}`,
              changefreq: `daily`,
              priority: 0.7,
              lastmod: `${node.context.updated}`,
            };
          }),
      },
    },

Expected result

Expecting the sitemap to output entries with correct last-modified tags, ie:<lastmod>2020-08-03T01:54:49.000Z</lastmod>

Actual result

<lastmod>NaN-NaN-NaN</lastmod>

Environment

System:
OS: macOS 10.15.6
CPU: (8) x64 Intel(R) Core(TM) i7-6820HQ CPU @ 2.70GHz
Shell: 5.7.1 - /bin/zsh
Binaries:
Node: 12.17.0 - ~/.nvm/versions/node/v12.17.0/bin/node
npm: 6.14.7 - ~/.nvm/versions/node/v12.17.0/bin/npm
Languages:
Python: 2.7.16 - /usr/bin/python
Browsers:
Chrome: 84.0.4147.105
Safari: 13.1.2
npmPackages:
gatsby: ^2.24.4 => 2.24.4
gatsby-image: ^2.4.13 => 2.4.13
gatsby-plugin-catch-links: ^2.3.11 => 2.3.11
gatsby-plugin-feed-mdx: ^1.0.1 => 1.0.1
gatsby-plugin-google-analytics: ^2.3.11 => 2.3.11
gatsby-plugin-manifest: ^2.4.18 => 2.4.21
gatsby-plugin-mdx: ^1.2.27 => 1.2.27
gatsby-plugin-offline: ^3.2.18 => 3.2.18
gatsby-plugin-preact: ^4.0.9 => 4.0.9
gatsby-plugin-react-helmet: ^3.3.10 => 3.3.10
gatsby-plugin-robots-txt: ^1.5.1 => 1.5.1
gatsby-plugin-s3: ^0.3.3 => 0.3.4
gatsby-plugin-sharp: ^2.6.19 => 2.6.22
gatsby-plugin-sitemap: ^2.4.11 => 2.4.11
gatsby-plugin-styled-components: ^3.3.10 => 3.3.10
gatsby-remark-attr: ^0.1.0 => 0.1.0
gatsby-remark-external-links: 0.0.4 => 0.0.4
gatsby-remark-images: ^3.3.19 => 3.3.19
gatsby-remark-unwrap-images: ^1.0.2 => 1.0.2
gatsby-source-filesystem: ^2.3.20 => 2.3.23
gatsby-transformer-sharp: ^2.5.11 => 2.5.11
npmGlobalPackages:
gatsby-cli: 2.12.66

[fgambarino]

Hi @flikteoh,
since the format of the date you are using is ISO one, could you try to use - instead of lastmod - the lastmodISO property?

[vladar]

Hi @flikteoh

Sorry to hear you're running into an issue. To help us best begin debugging the underlying cause, it is incredibly helpful if you're able to create a minimal reproduction. This is a simplified example of the issue that makes it clear and obvious what the issue is and how we can begin to debug it.

If you're up for it, we'd very much appreciate if you could provide a minimal reproduction and we'll be able to take another look.

Thanks for using Gatsby! 💜

[vladar]

CC @moonmeister

[Joe-Edwards]

I just ran into this as well - the fix appears to be using lastmodISO as suggested above.

It's a little tricky to debug as the plugin is using an old version of the sitemap package, and more recent versions of the package don't have this distinction (see https://github.com/ekalinin/sitemap.js/blob/master/CHANGELOG.md#breaking-changes).

[moonmeister]

Sounds like #25670 will take care of this since it updates to the latest version.

[flikteoh]

@fgambarino Thank you so much. That fixes my problem.

Was wondering why isn't there any documentation regarding to this on the plugin page itself.
Whether is it lastmod or lastmodISO, I felt that it's somewhat important for users.

Also,

https://support.google.com/webmasters/answer/183668?hl=en
Google ignores <priority> and <changefreq> values, so don't bother adding them.
Google reads the <lastmod> value, but if you misrepresent this value, we will stop reading it.

and sorry @vladar I'm unable to create a minimal reproduction for this issue.

In case anyone that came across similar problem, this solved my problem:

via the lastmodISO

    {
      resolve: `gatsby-plugin-sitemap`,
      options: {
        query: `{
          site {
            siteMetadata {
              siteUrl
            }
          }

          allSitePage {
            nodes {
              path
              context {
                updated
              }
            }
          }
        }`,
        resolveSiteUrl: ({ site }) => site.siteMetadata.siteUrl,
        serialize: ({ site, allSitePage }) =>
          allSitePage.nodes.map((node) => {
            const { siteUrl } = site.siteMetadata;
            return {
              url: `${siteUrl}${node.path}`,
              lastmodISO: node.context.updated,
            };
          }),
        createLinkInHead: true,
      },
    },

[github-actions]

Hiya!

This issue has gone quiet. Spooky quiet. 👻

We get a lot of issues, so we currently close issues after 60 days of inactivity. It’s been at least 20 days since the last update here.
If we missed this issue or if you want to keep it open, please reply here. You can also add the label "not stale" to keep this issue open!
As a friendly reminder: the best way to see this issue, or any other, fixed is to open a Pull Request. Check out gatsby.dev/contribute for more information about opening PRs, triaging issues, and contributing!

Thanks for being a part of the Gatsby community! 💪💜