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Add provide/emit! geography article, update spreads article, fix foundations rendering

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- New geography article (provide.sx): four primitives, demos, nested scoping,
  adapter comparison, spec explorer links
- Updated spreads article section VI: provide/emit! is now implemented, not planned
- Fixed foundations.sx: ~docs/code-block → ~docs/code (undefined component
  was causing the page to silently fail to render)
- Added nav entry and defpage route for provide/emit! article

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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giles
2026-03-13 16:04:52 +00:00
parent 04d3b2ecaf
commit aef990735f
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;; ---------------------------------------------------------------------------
;; Provide / Context / Emit! — render-time dynamic scope
;; ---------------------------------------------------------------------------
;; ---- Demo components ----
(defcomp ~geography/demo-provide-basic ()
(div :class "space-y-2"
(provide "theme" {:primary "violet" :accent "rose"}
(div :class "rounded-lg p-3 bg-violet-50 border border-violet-200"
(p :class "text-sm text-violet-800 font-semibold" "Inside provider: theme.primary = violet")
(p :class "text-xs text-stone-500" "Child reads context value without prop threading.")))
(div :class "rounded-lg p-3 bg-stone-50 border border-stone-200"
(p :class "text-sm text-stone-600" "Outside provider: no theme context."))))
(defcomp ~geography/demo-emit-collect ()
(div :class "space-y-2"
(provide "scripts" nil
(div :class "rounded-lg p-3 bg-stone-50 border border-stone-200"
(p :class "text-sm text-stone-700"
(emit! "scripts" "analytics.js")
(emit! "scripts" "charts.js")
"Page content renders here. Scripts emitted silently."))
(div :class "rounded-lg p-3 bg-violet-50 border border-violet-200"
(p :class "text-sm text-violet-800 font-semibold" "Emitted scripts:")
(ul :class "text-xs text-stone-600 list-disc pl-5"
(map (fn (s) (li (code s))) (emitted "scripts")))))))
(defcomp ~geography/demo-spread-mechanism ()
(div :class "space-y-2"
(div (make-spread {:class "rounded-lg p-3 bg-rose-50 border border-rose-200"})
(p :class "text-sm text-rose-800 font-semibold" "Spread child styled this div")
(p :class "text-xs text-stone-500" "The spread emitted into the element-attrs provider."))
(let ((card (make-spread {:class "rounded-lg p-3 bg-amber-50 border border-amber-200"})))
(div card
(p :class "text-sm text-amber-800 font-semibold" "Stored spread, same mechanism")
(p :class "text-xs text-stone-500" "Bound to a let variable, applied when rendered as child.")))))
(defcomp ~geography/demo-nested-provide ()
(div :class "space-y-2"
(provide "level" "outer"
(div :class "rounded-lg p-3 bg-stone-50 border border-stone-200"
(p :class "text-sm text-stone-700"
(str "Level: " (context "level")))
(provide "level" "inner"
(div :class "rounded-lg p-3 bg-violet-50 border border-violet-200 ml-4"
(p :class "text-sm text-violet-700"
(str "Level: " (context "level")))))
(p :class "text-sm text-stone-500 mt-1"
(str "Back to: " (context "level")))))))
;; ---- Layout helper (reuse from spreads article) ----
(defcomp ~geography/provide-demo-example (&key demo code)
(div :class "grid grid-cols-1 lg:grid-cols-2 gap-4 my-6 items-start"
(div :class "border border-dashed border-stone-300 rounded-lg p-4 bg-stone-50 min-h-[80px]"
demo)
(div :class "not-prose bg-stone-100 rounded-lg p-4 overflow-x-auto"
(pre :class "text-sm leading-relaxed whitespace-pre-wrap break-words" (code code)))))
;; ---- Page content ----
(defcomp ~geography/provide-content ()
(~docs/page :title "Provide / Context / Emit!"
(p :class "text-stone-500 text-sm italic mb-8"
"Render-time dynamic scope. " (code "provide") " creates a named scope with a value "
"and an accumulator. " (code "context") " reads the value downward. "
(code "emit!") " appends to the accumulator upward. " (code "emitted") " retrieves what was emitted. "
"This is the substrate that spreads, CSSX, and script collection are built on.")
;; =====================================================================
;; I. The four primitives
;; =====================================================================
(~docs/section :title "Four primitives" :id "primitives"
(~docs/subsection :title "provide (special form)"
(p (code "provide") " creates a named scope with a value and an empty accumulator. "
"The body expressions execute with the scope active. When the body completes, "
"the scope is popped.")
(~docs/code :code (highlight "(provide name value\n body...)\n\n;; Example: theme context\n(provide \"theme\" {:primary \"violet\"}\n (h1 \"Title\") ;; can read (context \"theme\")\n (p \"Body\")) ;; scope active for all children" "lisp"))
(p (code "provide") " is a special form, not a function — the body is evaluated "
"inside the scope, not before it."))
(~docs/subsection :title "context"
(p "Reads the value from the nearest enclosing " (code "provide") " with the given name. "
"Errors if no provider and no default given.")
(~docs/code :code (highlight "(provide \"theme\" {:primary \"violet\" :font \"serif\"}\n (get (context \"theme\") :primary)) ;; → \"violet\"\n\n;; With default (no error when missing):\n(context \"theme\" {:primary \"stone\"}) ;; → {:primary \"stone\"}" "lisp")))
(~docs/subsection :title "emit!"
(p "Appends a value to the nearest enclosing provider's accumulator. "
"Tolerant: returns nil silently when no provider exists.")
(~docs/code :code (highlight "(provide \"scripts\" nil\n (emit! \"scripts\" \"analytics.js\")\n (emit! \"scripts\" \"charts.js\")\n ;; accumulator now has both scripts\n )\n\n;; Outside any provider — silently does nothing:\n(emit! \"scripts\" \"orphan.js\") ;; → nil, no error" "lisp"))
(p "Tolerance is critical. Spreads emit into " (code "\"element-attrs\"")
" — but a spread might be evaluated in a fragment, a " (code "begin") " block, or a "
(code "map") " call where no element provider exists. "
"Tolerant " (code "emit!") " means these cases silently vanish instead of crashing."))
(~docs/subsection :title "emitted"
(p "Returns the list of values emitted into the nearest provider with the given name. "
"Empty list if no provider.")
(~docs/code :code (highlight "(provide \"scripts\" nil\n (emit! \"scripts\" \"a.js\")\n (emit! \"scripts\" \"b.js\")\n (emitted \"scripts\")) ;; → (\"a.js\" \"b.js\")" "lisp"))))
;; =====================================================================
;; II. Two directions, one mechanism
;; =====================================================================
(~docs/section :title "Two directions, one mechanism" :id "directions"
(p (code "provide") " serves both downward and upward communication through a single scope.")
(~docs/table
:headers (list "Direction" "Read with" "Write with" "Example")
:rows (list
(list "Downward (scope → child)" "context" "provide value" "Theme, config, locale")
(list "Upward (child → scope)" "emitted" "emit!" "Script collection, spread attrs")))
(~geography/provide-demo-example
:demo (~geography/demo-provide-basic)
:code (highlight ";; Downward: theme context\n(provide \"theme\"\n {:primary \"violet\" :accent \"rose\"}\n (h1 :style (str \"color:\"\n (get (context \"theme\") :primary))\n \"Themed heading\")\n (p \"inherits theme context\"))" "lisp"))
(~geography/provide-demo-example
:demo (~geography/demo-emit-collect)
:code (highlight ";; Upward: script accumulation\n(provide \"scripts\" nil\n (div\n (emit! \"scripts\" \"analytics.js\")\n (div\n (emit! \"scripts\" \"charts.js\")\n \"chart\"))\n ;; Collect at the boundary:\n (for-each (fn (s)\n (script :src s))\n (emitted \"scripts\")))" "lisp")))
;; =====================================================================
;; III. How spreads use it
;; =====================================================================
(~docs/section :title "How spreads use provide/emit!" :id "spreads"
(p "Every element rendering function wraps its children in a provider scope "
"named " (code "\"element-attrs\"") ". When the adapter encounters a spread child, "
"it emits the spread's attrs into this scope. After all children render, the "
"element collects and merges the emitted attrs.")
(~geography/provide-demo-example
:demo (~geography/demo-spread-mechanism)
:code (highlight ";; Spread = emit! into element-attrs\n(div (make-spread {:class \"card\"})\n \"hello\")\n\n;; Internally:\n;; 1. div opens provider:\n;; (provide-push! \"element-attrs\" nil)\n;; 2. spread child emits:\n;; (emit! \"element-attrs\"\n;; {:class \"card\"})\n;; 3. div collects + merges:\n;; (emitted \"element-attrs\")\n;; → ({:class \"card\"})\n;; 4. (provide-pop! \"element-attrs\")\n;; Result: <div class=\"card\">hello</div>" "lisp"))
(~docs/subsection :title "Why this matters"
(p "Before the refactor, every intermediate form in the render pipeline — "
"fragments, " (code "let") ", " (code "begin") ", " (code "map") ", "
(code "for-each") ", " (code "when") ", " (code "cond") ", component children — "
"needed an explicit " (code "(filter (fn (r) (not (spread? r))) ...)") " to strip "
"spread values from rendered output. Over 25 such filters existed across the four adapters.")
(p "With provide/emit!, all of these disappear. Spreads emit into the nearest element's "
"scope regardless of how many layers of control flow they pass through. Non-element "
"contexts have no provider, so " (code "emit!") " is a silent no-op.")))
;; =====================================================================
;; IV. Nested scoping
;; =====================================================================
(~docs/section :title "Nested scoping" :id "nesting"
(p "Providers stack. Each " (code "provide") " pushes onto a per-name stack; "
"the closest one wins. This gives lexical-style scoping at render time.")
(~geography/provide-demo-example
:demo (~geography/demo-nested-provide)
:code (highlight "(provide \"level\" \"outer\"\n (context \"level\") ;; → \"outer\"\n (provide \"level\" \"inner\"\n (context \"level\")) ;; → \"inner\"\n (context \"level\")) ;; → \"outer\" again" "lisp"))
(p "For " (code "emit!") ", this means emissions go to the " (em "nearest") " provider. "
"A spread inside a nested element emits to that element, not an ancestor.")
(~docs/code :code (highlight ";; Nested elements = nested providers\n(div ;; provider A\n (span ;; provider B\n (make-spread {:class \"inner\"})) ;; emits to B\n (make-spread {:class \"outer\"})) ;; emits to A\n;; → <div class=\"outer\"><span class=\"inner\"></span></div>" "lisp")))
;; =====================================================================
;; V. Across all adapters
;; =====================================================================
(~docs/section :title "Across all adapters" :id "adapters"
(p "The provide/emit! mechanism works identically across all four rendering adapters. "
"The element rendering pattern is the same; only the output format differs.")
(~docs/table
:headers (list "Adapter" "Element render" "Spread dispatch")
:rows (list
(list "HTML (server)" "provide-push! → render children → merge emitted → provide-pop!" "(emit! \"element-attrs\" (spread-attrs expr)) → \"\"")
(list "Async (server)" "Same pattern, with await on child rendering" "Same dispatch")
(list "SX wire (aser)" "provide-push! → serialize children → merge emitted as :key attrs → provide-pop!" "(emit! \"element-attrs\" (spread-attrs expr)) → nil")
(list "DOM (browser)" "provide-push! → reduce children → merge emitted onto DOM element → provide-pop!" "emit! + keep value for reactive-spread detection")))
(~docs/subsection :title "DOM adapter: reactive-spread preserved"
(p "In the DOM adapter, spread children inside islands are still checked individually "
"for signal dependencies. " (code "reactive-spread") " tracks signal deps and "
"surgically updates attributes when signals change. The static path uses provide/emit!; "
"the reactive path wraps it in an effect.")
(p "See the "
(a :href "/sx/(geography.(spreads))" :class "text-violet-600 hover:underline" "spreads article")
" for reactive-spread details.")))
;; =====================================================================
;; VI. Comparison with collect!
;; =====================================================================
(~docs/section :title "Comparison with collect! / collected" :id "comparison"
(~docs/table
:headers (list "" "provide / emit!" "collect! / collected")
:rows (list
(list "Scope" "Lexical (nearest enclosing provide)" "Global (render-wide)")
(list "Deduplication" "None — every emit! appends" "Automatic (same value skipped)")
(list "Multiple scopes" "Yes — nested provides shadow" "No — single global bucket per name")
(list "Downward data" "Yes (context)" "No")
(list "Used by" "Spreads (element-attrs)" "CSSX rule accumulation")))
(p (code "collect!") " remains the right tool for CSS rule accumulation — deduplication "
"matters there, and rules need to reach the layout root regardless of nesting depth. "
(code "emit!") " is right for spread attrs — no dedup needed, and each element only "
"wants attrs from its direct children."))
;; =====================================================================
;; VII. Platform implementation
;; =====================================================================
(~docs/section :title "Platform implementation" :id "platform"
(p "Each platform (Python, JavaScript) must provide five operations. "
"The platform manages per-name stacks — each stack entry has a value and an "
"emitted list.")
(~docs/table
:headers (list "Platform primitive" "Purpose")
:rows (list
(list "provide-push!(name, value)" "Push a new scope with value and empty emitted list")
(list "provide-pop!(name)" "Pop the most recent scope")
(list "context(name, ...default)" "Read value from nearest scope (error if missing and no default)")
(list "emit!(name, value)" "Append to nearest scope's emitted list (tolerant: no-op if missing)")
(list "emitted(name)" "Return list of emitted values from nearest scope")))
(p (code "provide") " itself is a special form in "
(a :href "/sx/(language.(spec.(explore.evaluator)))" :class "font-mono text-violet-600 hover:underline text-sm" "eval.sx")
" — it calls " (code "provide-push!") ", evaluates the body, "
"then calls " (code "provide-pop!") ". The five platform primitives are declared in "
(a :href "/sx/(language.(spec.(explore.boundary)))" :class "font-mono text-violet-600 hover:underline text-sm" "boundary.sx")
" (Tier 5: Dynamic scope).")
(~docs/note
(p (strong "Spec explorer: ") "See the provide/emit! primitives in "
(a :href "/sx/(language.(spec.(explore.boundary)))" :class "font-mono text-violet-600 hover:underline text-sm" "boundary.sx explorer")
". The " (code "provide") " special form is in "
(a :href "/sx/(language.(spec.(explore.evaluator)))" :class "font-mono text-violet-600 hover:underline text-sm" "eval.sx explorer")
". Element rendering with provide/emit! is visible in "
(a :href "/sx/(language.(spec.(explore.adapter-html)))" :class "font-mono text-violet-600 hover:underline text-sm" "adapter-html")
" and "
(a :href "/sx/(language.(spec.(explore.adapter-async)))" :class "font-mono text-violet-600 hover:underline text-sm" "adapter-async")
".")))))