Tests on Windows fail - reasons and ways to fix

[vtenfys]

cc @calcsam re: https://github.com/orgs/gatsbyjs/teams/maintainers/discussions/30/comments/7

Tests on Windows are broken due to two specific issues, which only affect a single package (gatsby-codemods). Both of these are technically upstream issues, rather than issues with Gatsby itself.

TL;DR we need to update @babel/core to at least 7.0.0-rc.3 (the hard part) and change one line in a single file.

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Global GraphQL transforms (generated by gatsby-codemods/global-graphql-calls) output with the native system line-endings, rather than always using \n. This causes its jscodeshift tests to fail, since unlike Jest's built-in snapshot testing, jscodeshift's fixture tests don't normalise line endings.

To fix this, change the following line in gatsby-codemods/src/global-graphql-calls.js from:

return root.toSource({ quote: `single` })

to:

return root.toSource({ quote: `single`, lineTerminator: `\n` })

...so that the generated files match the snapshots, which use \n endings, rather than \r\n on Windows. Alternatively, to fix the root cause of the issue, a PR could be sent to jscodeshift so that it normalises line endings when performing fixture tests.

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Babel's --ignore **/__tests__ option is buggy on Windows with version 7.0.0-beta.52. Basically Babel converts globs to a regex, and then matches all files against this regex - internally this works a bit differently between Babel 7.0.0-beta.52 (which Gatsby is currently using) and 7.0.0-rc.3 (the latest version) - previously Babel used minimatch to do the conversion, but with the latest RC, it's been rewritten so that it does the conversion itself. So basically, to fix this issue we just need to update Babel to at least 7.0.0-rc.3.

Sidenote: the following line in .babel-preset.js needs to be changed to upgrade to Babel 7 rc3:

Various other problems occur but these are package-specific, whereas ALL builds will fail without this change.

[vtenfys]

I'm currently working on upgrading Gatsby to the latest version of Babel (mostly just fixing config options / tests which have changed).