fix(gatsby-link): trailing slash undefined check for prod env

[imjoshin]

Description

We weren't checking for __TRAILING_SLASH__ not being set in prod environments. I wanted to add a test for this as well, but looks like we do similar checks elsewhere so we can't utest this in a simulated prod environment.

If anyone looks at this in the future, here's the test we could add:

['development', 'production'].forEach(nodeEnv => {
  it(`handles option not set in ${nodeEnv} (legacy behavior)`, () => {
    process.env.NODE_ENV = nodeEnv
    delete global.__TRAILING_SLASH__
    expect(rewriteLinkPath(`/path`, `/`)).toBe(`/path`)
    expect(rewriteLinkPath(`/path/`, `/`)).toBe(`/path/`)
    expect(rewriteLinkPath(`/path#hash`, `/`)).toBe(`/path#hash`)
    expect(rewriteLinkPath(`/path?query_param=hello`, `/`)).toBe(
      `/path?query_param=hello`
    )
    expect(rewriteLinkPath(`/path?query_param=hello#anchor`, `/`)).toBe(
      `/path?query_param=hello#anchor`
    )
  })
})

Note: I did run this test to duplicate the error. Then, I added the fix and saw a different error than the __TRAILING_SLASH__ is not defined error, and that fell into a similar check later on in the trailing slash flow. (checking for __BASE_PATH__ in https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-link/src/index.js#L33).

Related Issues

[sc-45955]

[pieh]

Thank you!

[imjoshin]

Published in gatsby-link@4.7.1