fix(gatsby-transformer-remark): properly bubble up errors thrown in subplugins

[tmfelwu]

This allow gatsby-remark-* subplugins to not have special error handling - gatsby will properly panic on build, but dev server won't crash anymore

[pieh]

This will cause gatsby build to not terminate and might cause broken (but successful) builds. We should wrap katex.renderToString calls in try/catch and use reporter.panicOnBuild (it was fixed some time ago)

[tmfelwu]

I didn't check if the build will terminate or not, but i dont think that should happen. anyways if reporter.panicOnBuild is fixed I will use that.

[pieh]

I didn't check if the build will terminate or not, but i dont think that should happen.

Can you elaborate what do You mean? I don't think we want to build be succesful if there are any errors.

[hexrcs]

@sparshy @pieh

Hi guys I tried to make use of reporter.panicOnBuild and added two new test cases, but I wasn't able to get the tests run properly (apparently panicOnBuild quits the test runner process immediately). Would be awesome if someone could help with this and review those changes! 😀

Edit: OK, fixed by using a mock process, now the new unit tests are passing! The lint:other tests failed on packages/gatsby-plugin-google-gtag/README.md, which is unrelated to what this PR is trying to fix. A review would be awesome!

[hexrcs]

Also it was weird that the linting tests were failing due to some markdown files in other packages 🤔

[pieh]

You can mock reporter.panicOnBuild instead of mocking process.exit (like in here https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby/src/bootstrap/load-plugins/__tests__/validate.js) and then we only need 1 test (if panicOnBuild was called when there is error)

[hexrcs]

@pieh

Cool, didn't think of that! Updated!

[pieh]

I've spend some time local testing it and uncovered that catching this in katex plugin isn't really optimal - we do output error, but because of the caching that we do in gatsby-tranformer-remark, gatsby will actually think that query results are correct and will cache malformatted results.

When I added more error handling in gatsby-trasnformer-remark (instead of katex) I was able to get more meaningful errors (using error handling that we have in gatsby which will report where this is happening - so add more context):

error
The GraphQL query from /Users/misiek/dev/gatsby/examples/using-remark/src/templates/template-blog-post.js failed.

Errors:
  KaTeX parse error: Expected group after '^' at position 14: a^2 + b^2 = d^̲

  GraphQL request (5:5)
  4:   markdownRemark(fields: {slug: {eq: $slug}}) {
  5:     htmlAst
         ^
  6:     timeToRead
  ,KaTeX parse error: Expected group after '^' at position 14: a^2 + b^2 = d^̲

  GraphQL request (6:5)
  5:     htmlAst
  6:     timeToRead
         ^
  7:     tableOfContents
  ,KaTeX parse error: Expected group after '^' at position 14: a^2 + b^2 = d^̲

  GraphQL request (7:5)
  6:     timeToRead
  7:     tableOfContents
         ^
  8:     fields {

URL path:
  /katex/
Context:
  {
    "slug": "/katex/"
  }
Plugin:
  none
Query:
  query usersMisiekDevGatsbyExamplesUsingRemarkSrcTemplatesTemplateBlogPostJs4084396848(
    $slug: String!
  ) {
    markdownRemark(fields: {slug: {eq: $slug}}) {
      htmlAst
      timeToRead
      tableOfContents
      fields {
        tagSlugs
      }
      frontmatter {
        title
        tags
        date(formatString: "MMMM DD, YYYY")
        author {
          id
          bio
          avatar {
            children {
              __typename
              ... on ImageSharp {
                fixed(width: 50, height: 50, quality: 75, grayscale: true) {
                  ...GatsbyImageSharpFixed
                }
              }
            }
          }
        }
      }
    }
  }

  fragment GatsbyImageSharpFixed on ImageSharpFixed {
    base64
    width
    height
    src
    srcSet
  }

I'll clean up my messy code and push it here - sounds good?

[hexrcs]

@pieh That would be awesome!

[pieh]

Thanks @sparshy and @hexrcs for help here!

[gatsbot]

Holy buckets, @sparshy — we just merged your PR to Gatsby! 💪💜

Gatsby is built by awesome people like you. Let us say “thanks” in two ways:

1. We’d like to send you some Gatsby swag. As a token of our appreciation, you can go to the Gatsby Swag Store and log in with your GitHub account to get a coupon code good for one free piece of swag. (Currently we’ve got a couple t-shirts available, plus some socks that are really razzing our berries right now.)
2. We just invited you to join the Gatsby organization on GitHub. This will add you to our team of maintainers. Accept the invite by visiting https://github.com/orgs/gatsbyjs/invitation. By joining the team, you’ll be able to label issues, review pull requests, and merge approved pull requests.

If there’s anything we can do to help, please don’t hesitate to reach out to us: tweet at @gatsbyjs and we’ll come a-runnin’.

Thanks again!