Make trailingSlash: 'always' default

[bluwy]

Changes

• Improve trailingSlash experience roadmap#983

There's a lot of work needed to update the test, but creating a stop gap here as something we could discuss before doing more work.

The reason for this change is highlighted in the roadmap link above. For static sites, this should not be a breaking change. For SSR sites, this will be a breaking change for on-demand pages which will now have a trailing slash by default. But you can revert to the previous behaviour for now if you want to not deal with this for now.

Testing

Docs

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[matthewp]

I'm not sure that Astro should have an opinion on trailingSlash vs not, this is mostly an aesthetic preference. I'm worried even having such a default might turn some people away from using Astro.

From the RFC discussion, it seems the problem this is trying to fix is with build.format of file, could the trailingSlash default to 'never' with that format? I could even see disallowing 'always' with file since that should be impossible to make work.

[bluwy]

Ignoring trailing slash has an impact on SEO and reducing potential duplicate work, so I don't think it's only an aesthetic preference. For example, Next and Nuxt have trailingslash as false/'never' by default. (AFAIA only sveltekit is ignore like us). We can't go with trailingSlash: 'never' like Next and Nuxt because we already have build.format: 'directory' by default, which will cause more conflicts (and directory feels like an Astro opinion to me too 😄)

For SSG, we technically already have trailingSlash: 'always' implied by default because of build.format: 'directory'. Our sites have trailing slashes by default: https://docs.astro.build/en/basics/project-structure/ and https://astro.build/blog/images/

I don't think the RFC discussion is only about build.format: 'file', it's for both file and directory. You need them to match this way to prevent relative path issues:

build.format	trailingSlash
file	never
directory	always

If you build your file to dist/foo/index.html, you cannot access it with example.com/foo (no trailing slash, which 'ignore' by default allows).

[matthewp]

Going to take the discussion over to the RFC thread so that this can focus on code review.

[matthewp]

blocked while the change is being debated

[bluwy]

The changes here are outdated