Gatsby: Modification times 💩

[zslabs]

Summary

I'm using the following snippet to automatically add file modification times to certain pieces of content on our site:

fs.statSync(node.fileAbsolutePath).mtime

I was scratching my brain at this one for a while, because my local builds do show differences in those dates, but on production they all show the last deploy date.

I did some digging and it looks like this is a “git” issue https://stackoverflow.com/a/48427454/1026742 (that answer is from someone that works at Netlify).

What I'd ideally like to do is have a hook that runs each time a file is saved. In my case, from the Netlify CMS UI, but also locally; where I could update a frontmatter field that I'd tag as something like, updatedDate. I looked at the Node API and didn't see anything that'd fit my needs, but I may also be missing something.

Anyone have tips on the best way to tackle this; OR (hopefully) something simple I'm missing that'd make this easier for content creators on my team? Thanks!

[zslabs]

To put this a bit more generally since I know ☝️is a mouthful; is there a hook "on-save" of content that I can use to modify frontmatter data?

[DSchau]

Not sure exactly what type of content you're trying to augment, but this sounds like a good use case for onCreateNode

The general idea would be something like this:

exports.onCreateNode = ({ actions: { createNodeField }, node }) => {
  const type = node.internal.type;
  if (type === 'MarkdownRemark') {
    createNodeField({
      node,
      name: `modifiedTime`,
      value: `compute_value_you_want_here`
    })
  }
}

this will create a query-able fields object, e.g.

query GetAllMarkdownContent {
  allMarkdownRemark {
    edges {
      node {
        fields {
          modifiedTime
        }
      }
    }
  }
}

[zslabs]

Hey @DSchau thanks for the reply. That's actually where I'm doing it 😄

Great that I'm following a recommendation, but sucks that the mtime is basically moot being pulled from a repo on Netlify and built on theirs.

[DSchau]

What about adding an explicit creationDate field in the frontmatter? If it's a git issue, I'm not sure we can work around that in Gatsby apart from something manual like setting the metadata explicitly!

[zslabs]

Yep, I've got a date field in there already for creation, but we'd like to use a modification date for things like tutorials; where context of when it was last updated could be helpful. I guess since there isn't any persistence on the file I can count on, it sounds like a manual field would probably be best.

Definitely not an issue with Gatsby, but something I figured would be worth asking. Thanks for chatting with me on this one!

[docwhat]

Just adding some info for anyone who finds this via google (like me!):

• You could just update the mtime on all the files. e.g., StackOverflow's _Restore a file's modification time in Git_.
• You could fetch the author time of the last commit: git log -1 --pretty=format:%aI -- package.json

• You could fetch the author time of the most recent commit: git log --pretty=format:%aI -- package.json | sort | tail -n 1

  The most recent commit can be different depending on how things are merged. For a single user blog that nobody submits PRs for (like mine) then the last commit is sufficient.

• If you prefer the committer time, use %cI instead of %aI.

  The author time is when the change was authored and the committer time is when the change was applied to git.

[andreasvirkus]

Just adding something else to future Googlers:
Saber now has this solved elegantly via a plugin! https://github.com/saberland/saber/tree/master/packages/saber-plugin-git-modification-time