Flat pageContext

[brillout]

Plan

• Flatten pageContext: merge all nested pageContext values directly onto pageContext => for a "think-free" pageContext that "just works".
• Source information at pageContext.source: where the value comes from.
• Precise access at pageContext.from: for conflict-free access.

Behind the scene, pageContext is a Proxy: upon property access the proxy goes through all sources (in a sensible order) and returns the first value it finds.

Examples

• pageContext.user
  • pageContext.from.request.user (equivalent value, assuming there isn't any conflict)
  • pageContext.source.user: Source (see Source down below)
• pageContext.Page: Component
  • pageContext.from.config[configFilePath].Page: Component
  • pageContext.from.configsOverridable.Page: SourceConfigsOverridable
  • pageContext.source.Page: Source
• pageContext.passToClient: string
  • pageContext.from.configsCumulative.passToClient: SourceConfigsCumulative
  • pageContext.from.config[configFilePath].passToClient: string
  • pageContext.source.passToClient: Source
• pageContext.isClientSideRenderable:
  • pageContext.from.configsComputed.isClientSideRenderable: SourceConfigsComputed
  • pageContext.source.isClientSideRenderable: Source
• pageContext.data: Data
  • pageContext.from.hooks.data: SourceHooks
  • pageContext.from.hook[hookFilePath].data: Data
  • pageContext.source.data: Source
• pageContext.locale: string
  • pageContext.from.renderFailure[0].from.hooks.locale (see Make original pageContext accessible to error page #1112)
  • pageContext.from.renderFailure[0].from.hook[hookFilePath].locale
  • pageContext.source.locale: Source
• pageContext.pageId as well as:
  • pageContext.from.internal.pageId
  • pageContext.source.pageId: Source

Also:

• pageContext.sources[0].Layout: Source
• pageContext.sources[1].Layout: Source
• ...

Use cases

• Easier DX.
• Adds all request properties to pageContext. (No need for the user to set pageContextInit anymore.)
• Preserve pageContext of failed rendering, see Make original pageContext accessible to error page #1112.
• Resolve conflicts. (That's why pageContext.from needs to hold value.)
• Config validation.(E.g. Config document.title defined at ${pageContext.from.configsCumulative.document.values[i].definedAt} should be a string.)
• Debug. (That's the only purpose of pageContext.from.config[configFilePath] and pageContext.from.hook[hookFilePath].)

Data Structures

// pageContext.source: Record<string, Source>

type Source = SourceConfigs | SourceHooks | SourceRenderFailure | SourceInternal | SourceRequest

type SourceInternal = {
  type: 'internal'
  value: unknown
}

type SourceRequest = {
  type: 'request'
  value: unknown
}

type SourceRenderFailure = {
  type: 'renderFailure'
  renderCount: number
  source: Source
}

type SourceHooks = {
  type: 'hooks'
  value: unknown, // e.g. `{ product: { name: 'iPhone', price: '499' } }`
  hookName: string // hook name e.g. 'data'
  definedAt: string
}

type SourceConfigs =
 | SourceConfigsOverridable
 | SourceConfigsCumulative
 | SourceConfigsComputed
/* Potential upcoming feature: resolve cumulative values at config-time instead of runtime,
   in order to save KBs on the client-side.
 | SourceConfigsResolved
 */

type SourceConfigsOverridable = {
  type: 'configsOverridable'
  value: unknown,
  definedAt: string
}
type SourceConfigsCumulative = {
  type: 'configsCumulative'
  values: {
      value: unknown,
      definedAt: string
  }[]
}
type SourceConfigsComputed = {
  type: 'configsComputed'
  value: unknown
}

See also

• Make the pageContext from previous render attempts accessible #1846
• Make original pageContext accessible to error page #1112

• vike/vike/client/client-routing-runtime/renderPageClientSide.ts

  Line 297 in bd49cc6

  // Make it public as `pageContext.previous`? Maybe after https://github.com/vikejs/vike/issues/1268

• [Discussion] universal-middleware/hono vike-node#26 (comment)