Gatsby: Handle errors in frontmatter

[discordianfish]

Description

Maybe I'm doing something wrong, but it seems gatsby doesn't warn/error on syntax errors in frontmatter sections.

Environment

Gatsby version: 1.9.166

Actual result

Pages with syntax errors in frontmatter section get siliently ignored.

Expected behavior

Gatsby should error out or at least warn about this.

[KyleAMathews]

This is where we parse the markdown files and their frontmatter https://github.com/gatsbyjs/gatsby/blob/77794d2916c927316b3c3ae55a0d4c1d8de88e3e/packages/gatsby-transformer-remark/src/on-node-create.js#L20

Could you investigate if graymatter does expose errors and if so, make a PR sending those to the console?

[flipactual]

Full output

error Plugin gatsby-transformer-remark returned an error


YAMLException: can not read a block mapping entry; a multiline key may not be an implicit key at line 7, column 1:

      ^


loader.js:165 generateError

[literally.fyi]/[js-yaml]/lib/js-yaml/loader.js:165:10
loader.js:171 throwError

[literally.fyi]/[js-yaml]/lib/js-yaml/loader.js:171:9
loader.js:1046 readBlockMapping

[literally.fyi]/[js-yaml]/lib/js-yaml/loader.js:1046:9
loader.js:1332 composeNode

[literally.fyi]/[js-yaml]/lib/js-yaml/loader.js:1332:12
loader.js:1492 readDocument

[literally.fyi]/[js-yaml]/lib/js-yaml/loader.js:1492:3
loader.js:1548 loadDocuments

[literally.fyi]/[js-yaml]/lib/js-yaml/loader.js:1548:5
loader.js:1569 load

[literally.fyi]/[js-yaml]/lib/js-yaml/loader.js:1569:19
loader.js:1591 Object.safeLoad

[literally.fyi]/[js-yaml]/lib/js-yaml/loader.js:1591:10
parse.js:12 module.exports

[literally.fyi]/[gray-matter]/lib/parse.js:12:17
index.js:94 parseMatter

[literally.fyi]/[gray-matter]/index.js:94:15
index.js:46 matter

[literally.fyi]/[gray-matter]/index.js:46:10
on-node-create.js:49 Object._callee$

[literally.fyi]/[gatsby-transformer-remark]/on-node-create.js:49:20
next_tick.js:150 process._tickCallback

internal/process/next_tick.js:150:11

This is the existing behavior (surfacing the error from within gray-matter) and it feels adequate to me, but how do you feel about it @discordianfish? Can you provide steps to reproduce the situation where a syntax error doesn't result in a logged error like this?

[discordianfish]

@flipactual Oh that's awesome! I think this is totally sufficient. Bonus points though for showing the line(s) what couldn't be parsed. But great either way!

[flipactual]

@discordianfish to be clear – I didn't do anything 😄 This is what happened when I tried to reproduce the problem, so maybe it's been fixed along the way somehow

Feel encouraged to reopen if you see the issue again, and we'll dig back in!