46 lines
2.3 KiB
Markdown
46 lines
2.3 KiB
Markdown
---
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title: Paths in Quartz
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---
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Paths are pretty complex to reason about because, especially for a static site generator, they can come from so many places.
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The current browser URL? Technically a path. A full file path to a piece of content? Also a path. What about a slug for a piece of content? Yet another path.
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It would be silly to type these all as `string` and call it a day as it's pretty common to accidentally mistake one type of path for another. Unfortunately, TypeScript does not have [nominal types](https://en.wikipedia.org/wiki/Nominal_type_system) for type aliases meaning even if you made custom types of a server-side slug or a client-slug slug, you can still accidentally assign one to another and TypeScript wouldn't catch it.
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Luckily, we can mimic nominal typing using [brands](https://www.typescriptlang.org/play#example/nominal-typing).
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```typescript
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// instead of
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type ClientSlug = string
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// we do
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type ClientSlug = string & { __brand: "client" }
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// that way, the following will fail typechecking
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const slug: ClientSlug = "some random slug"
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```
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While this prevents most typing mistakes *within* our nominal typing system (e.g. mistaking a server slug for a client slug), it doesn't prevent us from *accidentally* mistaking a string for a client slug when we forcibly cast it.
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Thus, we still need to be careful when casting from a string to one of these nominal types in the 'entrypoints', illustrated with hexagon shapes in the diagram below.
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The following diagram draws the relationships between all the path sources, nominal path types, and what functions in `quartz/path.ts` convert between them.
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```mermaid
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graph LR
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Browser{{Browser}} --> Window{{Window}} & LinkElement{{Link Element}}
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Window --"getCanonicalSlug()"--> Canonical[Canonical Slug]
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Window --"getClientSlug()"--> Client[Client Slug]
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LinkElement --".href"--> Relative[Relative URL]
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Client --"canonicalizeClient()"--> Canonical
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Canonical --"pathToRoot()"--> Relative
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Canonical --"resolveRelative()" --> Relative
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MD{{Markdown File}} --> FilePath{{File Path}} & Links[Markdown links]
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Links --"transformLink()"--> Relative
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FilePath --"slugifyFilePath()"--> Server[Server Slug]
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Server --> HTML["HTML File"]
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Server --"canonicalizeServer()"--> Canonical
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style Canonical stroke-width:4px
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```
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