feat(docs): 678 — routing demo that switches on a page route atom - #108

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feat(docs): 678 — routing demo that switches on a page route atom#108
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@randomdevpeterandomdevpete commented Aug 21, 2026

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Summary

A deliberately minimal routing demo: one route atom holds which of a fixed set of pages the URL
names, a plain switch on its value picks the component to render, and the nav buttons navigate by
setting that atom instead of rendering <Link>s. It imports nothing from jarl-react — no Link,
Route or Switch component appears anywhere in SwitchRoutingApp.tsx.

The setRouteAtom question

The ticket left open whether to add a setRouteAtom primitive to jarl-atoms or approximate the
same shape with existing pieces. This PR approximates it: the fixed-set page segment is a
paramRouteAtom narrowed by a transformRouteAtom, the same composition numericRouteAtom's own
docstring calls "the usual way to build a constrained segment from the existing primitives". The
explicit generics on that transformRouteAtom call (<{ page: string }, { page: SwitchRoutingPage }>) are load-bearing: they pin the atom's value to the SwitchRoutingPage union rather than letting
it widen to string, which is what lets the switch in pageView be exhaustive with no default
case. Confirmed by typechecking the branch directly (tsc reports no errors on the new files, and the
same pre-existing, unrelated errors — missing @emotion/styled/highlight.js types, a generated
source-files.json — appear identically on the base branch).

No new export was added to jarl-atoms. setRouteAtom collides with jotai's own write vocabulary —
this demo already calls useSetAtom(pageRoute), and useSetAtom(setRouteAtom(...)) would fight
itself — and the base branch (#97) already composes constrained segments the same way, locally, for
its own demo (dateSegmentRouteAtom/filenameRouteAtom in ComplexRoutingApp.tsx, neither
exported).

Ticket 927 tracks a properly-named oneOfRouteAtom primitive for jarl-atoms, filed to land once
789 does.

Stack

Stacked on #97 (ticket 677), which this ticket depends on. Targets
task-677-complex-routing-demo-custom-path-atoms, not master.

@randomdevpete
feat(docs): 678 — routing demo that switches on a page route atom
b8adab4
A deliberately minimal demo: one route atom holds which of a fixed set of
pages the URL names, a plain `switch` on its value picks the component, and
the nav buttons navigate by writing that atom. It imports nothing from
`jarl-react` - no `Link`, `Route` or `Switch` component anywhere in it.
The fixed set is composed from existing exports rather than a new primitive:
a `paramRouteAtom` narrowed by a `transformRouteAtom`, the same composition
`numericRouteAtom` documents, which also types the value as the union the
switch needs so its cases are exhaustive.
Ticket: 678
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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
feat(docs): 678 — routing demo that switches on a page route atom - #108
Draft
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Draft
feat(docs): 678 — routing demo that switches on a page route atom#108
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Conversation
@randomdevpete
@randomdevpeterandomdevpete
commented
Aug 21, 2026

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Owner
Summary
A deliberately minimal routing demo: one route atom holds which of a fixed set of pages the URL

names, a plain switch on its value picks the component to render, and the nav buttons navigate by

setting that atom instead of rendering <Link>s. It imports nothing from jarl-react — no Link,
Route or Switch component appears anywhere in SwitchRoutingApp.tsx.
The setRouteAtom question
The ticket left open whether to add a setRouteAtom primitive to jarl-atoms or approximate the

same shape with existing pieces. This PR approximates it: the fixed-set page segment is a
paramRouteAtom narrowed by a transformRouteAtom, the same composition numericRouteAtom's own

docstring calls "the usual way to build a constrained segment from the existing primitives". The

explicit generics on that transformRouteAtom call (<{ page: string }, { page: SwitchRoutingPage }>) are load-bearing: they pin the atom's value to the SwitchRoutingPage union rather than letting

it widen to string, which is what lets the switch in pageView be exhaustive with no default

case. Confirmed by typechecking the branch directly (tsc reports no errors on the new files, and the

same pre-existing, unrelated errors — missing @emotion/styled/highlight.js types, a generated
source-files.json — appear identically on the base branch).
No new export was added to jarl-atoms. setRouteAtom collides with jotai's own write vocabulary —

this demo already calls useSetAtom(pageRoute), and useSetAtom(setRouteAtom(...)) would fight

itself — and the base branch (#97) already composes constrained segments the same way, locally, for

its own demo (dateSegmentRouteAtom/filenameRouteAtom in ComplexRoutingApp.tsx, neither

exported).
Ticket 927 tracks a properly-named oneOfRouteAtom primitive for jarl-atoms, filed to land once

789 does.
Stack
Stacked on #97 (ticket 677), which this ticket depends on. Targets
task-677-complex-routing-demo-custom-path-atoms, not master.
@randomdevpete
feat(docs): 678 — routing demo that switches on a page route atom
b8adab4
A deliberately minimal demo: one route atom holds which of a fixed set of
pages the URL names, a plain `switch` on its value picks the component, and
the nav buttons navigate by writing that atom. It imports nothing from
`jarl-react` - no `Link`, `Route` or `Switch` component anywhere in it.
The fixed set is composed from existing exports rather than a new primitive:
a `paramRouteAtom` narrowed by a `transformRouteAtom`, the same composition
`numericRouteAtom` documents, which also types the value as the union the
switch needs so its cases are exhaustive.
Ticket: 678
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
feat(docs): 678 — routing demo that switches on a page route atom - #108
Draft
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Draft
feat(docs): 678 — routing demo that switches on a page route atom#108
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Conversation
@randomdevpete
@randomdevpeterandomdevpete
commented
Aug 21, 2026

Copy link


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Owner
Summary
A deliberately minimal routing demo: one route atom holds which of a fixed set of pages the URL

names, a plain switch on its value picks the component to render, and the nav buttons navigate by

setting that atom instead of rendering <Link>s. It imports nothing from jarl-react — no Link,
Route or Switch component appears anywhere in SwitchRoutingApp.tsx.
The setRouteAtom question
The ticket left open whether to add a setRouteAtom primitive to jarl-atoms or approximate the

same shape with existing pieces. This PR approximates it: the fixed-set page segment is a
paramRouteAtom narrowed by a transformRouteAtom, the same composition numericRouteAtom's own

docstring calls "the usual way to build a constrained segment from the existing primitives". The

explicit generics on that transformRouteAtom call (<{ page: string }, { page: SwitchRoutingPage }>) are load-bearing: they pin the atom's value to the SwitchRoutingPage union rather than letting

it widen to string, which is what lets the switch in pageView be exhaustive with no default

case. Confirmed by typechecking the branch directly (tsc reports no errors on the new files, and the

same pre-existing, unrelated errors — missing @emotion/styled/highlight.js types, a generated
source-files.json — appear identically on the base branch).
No new export was added to jarl-atoms. setRouteAtom collides with jotai's own write vocabulary —

this demo already calls useSetAtom(pageRoute), and useSetAtom(setRouteAtom(...)) would fight

itself — and the base branch (#97) already composes constrained segments the same way, locally, for

its own demo (dateSegmentRouteAtom/filenameRouteAtom in ComplexRoutingApp.tsx, neither

exported).
Ticket 927 tracks a properly-named oneOfRouteAtom primitive for jarl-atoms, filed to land once

789 does.
Stack
Stacked on #97 (ticket 677), which this ticket depends on. Targets
task-677-complex-routing-demo-custom-path-atoms, not master.
@randomdevpete
feat(docs): 678 — routing demo that switches on a page route atom
b8adab4
A deliberately minimal demo: one route atom holds which of a fixed set of
pages the URL names, a plain `switch` on its value picks the component, and
the nav buttons navigate by writing that atom. It imports nothing from
`jarl-react` - no `Link`, `Route` or `Switch` component anywhere in it.
The fixed set is composed from existing exports rather than a new primitive:
a `paramRouteAtom` narrowed by a `transformRouteAtom`, the same composition
`numericRouteAtom` documents, which also types the value as the union the
switch needs so its cases are exhaustive.
Ticket: 678
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1 participant

@randomdevpete

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
feat(docs): 678 — routing demo that switches on a page route atom - #108
Draft
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Draft
feat(docs): 678 — routing demo that switches on a page route atom#108
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Conversation
@randomdevpete
@randomdevpeterandomdevpete
commented
Aug 21, 2026

Copy link


Copy Markdown

Owner
Summary
A deliberately minimal routing demo: one route atom holds which of a fixed set of pages the URL

names, a plain switch on its value picks the component to render, and the nav buttons navigate by

setting that atom instead of rendering <Link>s. It imports nothing from jarl-react — no Link,
Route or Switch component appears anywhere in SwitchRoutingApp.tsx.
The setRouteAtom question
The ticket left open whether to add a setRouteAtom primitive to jarl-atoms or approximate the

same shape with existing pieces. This PR approximates it: the fixed-set page segment is a
paramRouteAtom narrowed by a transformRouteAtom, the same composition numericRouteAtom's own

docstring calls "the usual way to build a constrained segment from the existing primitives". The

explicit generics on that transformRouteAtom call (<{ page: string }, { page: SwitchRoutingPage }>) are load-bearing: they pin the atom's value to the SwitchRoutingPage union rather than letting

it widen to string, which is what lets the switch in pageView be exhaustive with no default

case. Confirmed by typechecking the branch directly (tsc reports no errors on the new files, and the

same pre-existing, unrelated errors — missing @emotion/styled/highlight.js types, a generated
source-files.json — appear identically on the base branch).
No new export was added to jarl-atoms. setRouteAtom collides with jotai's own write vocabulary —

this demo already calls useSetAtom(pageRoute), and useSetAtom(setRouteAtom(...)) would fight

itself — and the base branch (#97) already composes constrained segments the same way, locally, for

its own demo (dateSegmentRouteAtom/filenameRouteAtom in ComplexRoutingApp.tsx, neither

exported).
Ticket 927 tracks a properly-named oneOfRouteAtom primitive for jarl-atoms, filed to land once

789 does.
Stack
Stacked on #97 (ticket 677), which this ticket depends on. Targets
task-677-complex-routing-demo-custom-path-atoms, not master.
@randomdevpete
feat(docs): 678 — routing demo that switches on a page route atom
b8adab4
A deliberately minimal demo: one route atom holds which of a fixed set of
pages the URL names, a plain `switch` on its value picks the component, and
the nav buttons navigate by writing that atom. It imports nothing from
`jarl-react` - no `Link`, `Route` or `Switch` component anywhere in it.
The fixed set is composed from existing exports rather than a new primitive:
a `paramRouteAtom` narrowed by a `transformRouteAtom`, the same composition
`numericRouteAtom` documents, which also types the value as the union the
switch needs so its cases are exhaustive.
Ticket: 678
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1 participant

@randomdevpete

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
feat(docs): 678 — routing demo that switches on a page route atom - #108
Draft
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Draft
feat(docs): 678 — routing demo that switches on a page route atom#108
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Conversation
@randomdevpete
@randomdevpeterandomdevpete
commented
Aug 21, 2026

Copy link


Copy Markdown

Owner
Summary
A deliberately minimal routing demo: one route atom holds which of a fixed set of pages the URL

names, a plain switch on its value picks the component to render, and the nav buttons navigate by

setting that atom instead of rendering <Link>s. It imports nothing from jarl-react — no Link,
Route or Switch component appears anywhere in SwitchRoutingApp.tsx.
The setRouteAtom question
The ticket left open whether to add a setRouteAtom primitive to jarl-atoms or approximate the

same shape with existing pieces. This PR approximates it: the fixed-set page segment is a
paramRouteAtom narrowed by a transformRouteAtom, the same composition numericRouteAtom's own

docstring calls "the usual way to build a constrained segment from the existing primitives". The

explicit generics on that transformRouteAtom call (<{ page: string }, { page: SwitchRoutingPage }>) are load-bearing: they pin the atom's value to the SwitchRoutingPage union rather than letting

it widen to string, which is what lets the switch in pageView be exhaustive with no default

case. Confirmed by typechecking the branch directly (tsc reports no errors on the new files, and the

same pre-existing, unrelated errors — missing @emotion/styled/highlight.js types, a generated
source-files.json — appear identically on the base branch).
No new export was added to jarl-atoms. setRouteAtom collides with jotai's own write vocabulary —

this demo already calls useSetAtom(pageRoute), and useSetAtom(setRouteAtom(...)) would fight

itself — and the base branch (#97) already composes constrained segments the same way, locally, for

its own demo (dateSegmentRouteAtom/filenameRouteAtom in ComplexRoutingApp.tsx, neither

exported).
Ticket 927 tracks a properly-named oneOfRouteAtom primitive for jarl-atoms, filed to land once

789 does.
Stack
Stacked on #97 (ticket 677), which this ticket depends on. Targets
task-677-complex-routing-demo-custom-path-atoms, not master.
@randomdevpete
feat(docs): 678 — routing demo that switches on a page route atom
b8adab4
A deliberately minimal demo: one route atom holds which of a fixed set of
pages the URL names, a plain `switch` on its value picks the component, and
the nav buttons navigate by writing that atom. It imports nothing from
`jarl-react` - no `Link`, `Route` or `Switch` component anywhere in it.
The fixed set is composed from existing exports rather than a new primitive:
a `paramRouteAtom` narrowed by a `transformRouteAtom`, the same composition
`numericRouteAtom` documents, which also types the value as the union the
switch needs so its cases are exhaustive.
Ticket: 678
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@randomdevpete

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
feat(docs): 678 — routing demo that switches on a page route atom - #108
Draft
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Draft
feat(docs): 678 — routing demo that switches on a page route atom#108
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Conversation
@randomdevpete
@randomdevpeterandomdevpete
commented
Aug 21, 2026

Copy link


Copy Markdown

Owner
Summary
A deliberately minimal routing demo: one route atom holds which of a fixed set of pages the URL

names, a plain switch on its value picks the component to render, and the nav buttons navigate by

setting that atom instead of rendering <Link>s. It imports nothing from jarl-react — no Link,
Route or Switch component appears anywhere in SwitchRoutingApp.tsx.
The setRouteAtom question
The ticket left open whether to add a setRouteAtom primitive to jarl-atoms or approximate the

same shape with existing pieces. This PR approximates it: the fixed-set page segment is a
paramRouteAtom narrowed by a transformRouteAtom, the same composition numericRouteAtom's own

docstring calls "the usual way to build a constrained segment from the existing primitives". The

explicit generics on that transformRouteAtom call (<{ page: string }, { page: SwitchRoutingPage }>) are load-bearing: they pin the atom's value to the SwitchRoutingPage union rather than letting

it widen to string, which is what lets the switch in pageView be exhaustive with no default

case. Confirmed by typechecking the branch directly (tsc reports no errors on the new files, and the

same pre-existing, unrelated errors — missing @emotion/styled/highlight.js types, a generated
source-files.json — appear identically on the base branch).
No new export was added to jarl-atoms. setRouteAtom collides with jotai's own write vocabulary —

this demo already calls useSetAtom(pageRoute), and useSetAtom(setRouteAtom(...)) would fight

itself — and the base branch (#97) already composes constrained segments the same way, locally, for

its own demo (dateSegmentRouteAtom/filenameRouteAtom in ComplexRoutingApp.tsx, neither

exported).
Ticket 927 tracks a properly-named oneOfRouteAtom primitive for jarl-atoms, filed to land once

789 does.
Stack
Stacked on #97 (ticket 677), which this ticket depends on. Targets
task-677-complex-routing-demo-custom-path-atoms, not master.
@randomdevpete
feat(docs): 678 — routing demo that switches on a page route atom
b8adab4
A deliberately minimal demo: one route atom holds which of a fixed set of
pages the URL names, a plain `switch` on its value picks the component, and
the nav buttons navigate by writing that atom. It imports nothing from
`jarl-react` - no `Link`, `Route` or `Switch` component anywhere in it.
The fixed set is composed from existing exports rather than a new primitive:
a `paramRouteAtom` narrowed by a `transformRouteAtom`, the same composition
`numericRouteAtom` documents, which also types the value as the union the
switch needs so its cases are exhaustive.
Ticket: 678
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
feat(docs): 678 — routing demo that switches on a page route atom - #108
Draft
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Draft
feat(docs): 678 — routing demo that switches on a page route atom#108
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Conversation
@randomdevpete
@randomdevpeterandomdevpete
commented
Aug 21, 2026

Copy link


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Owner
Summary
A deliberately minimal routing demo: one route atom holds which of a fixed set of pages the URL

names, a plain switch on its value picks the component to render, and the nav buttons navigate by

setting that atom instead of rendering <Link>s. It imports nothing from jarl-react — no Link,
Route or Switch component appears anywhere in SwitchRoutingApp.tsx.
The setRouteAtom question
The ticket left open whether to add a setRouteAtom primitive to jarl-atoms or approximate the

same shape with existing pieces. This PR approximates it: the fixed-set page segment is a
paramRouteAtom narrowed by a transformRouteAtom, the same composition numericRouteAtom's own

docstring calls "the usual way to build a constrained segment from the existing primitives". The

explicit generics on that transformRouteAtom call (<{ page: string }, { page: SwitchRoutingPage }>) are load-bearing: they pin the atom's value to the SwitchRoutingPage union rather than letting

it widen to string, which is what lets the switch in pageView be exhaustive with no default

case. Confirmed by typechecking the branch directly (tsc reports no errors on the new files, and the

same pre-existing, unrelated errors — missing @emotion/styled/highlight.js types, a generated
source-files.json — appear identically on the base branch).
No new export was added to jarl-atoms. setRouteAtom collides with jotai's own write vocabulary —

this demo already calls useSetAtom(pageRoute), and useSetAtom(setRouteAtom(...)) would fight

itself — and the base branch (#97) already composes constrained segments the same way, locally, for

its own demo (dateSegmentRouteAtom/filenameRouteAtom in ComplexRoutingApp.tsx, neither

exported).
Ticket 927 tracks a properly-named oneOfRouteAtom primitive for jarl-atoms, filed to land once

789 does.
Stack
Stacked on #97 (ticket 677), which this ticket depends on. Targets
task-677-complex-routing-demo-custom-path-atoms, not master.
@randomdevpete
feat(docs): 678 — routing demo that switches on a page route atom
b8adab4
A deliberately minimal demo: one route atom holds which of a fixed set of
pages the URL names, a plain `switch` on its value picks the component, and
the nav buttons navigate by writing that atom. It imports nothing from
`jarl-react` - no `Link`, `Route` or `Switch` component anywhere in it.
The fixed set is composed from existing exports rather than a new primitive:
a `paramRouteAtom` narrowed by a `transformRouteAtom`, the same composition
`numericRouteAtom` documents, which also types the value as the union the
switch needs so its cases are exhaustive.
Ticket: 678
Sign up for freeto join this conversation on GitHub.
Already have an account?
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No reviews


Assignees


No one assigned


Labels


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Development

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1 participant

@randomdevpete

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

Skip to content
feat(docs): 678 — routing demo that switches on a page route atom - #108
Draft
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Draft
feat(docs): 678 — routing demo that switches on a page route atom#108
randomdevpete wants to merge 1 commit into
task-677-complex-routing-demo-custom-path-atomsfrom 
task-678-very-simple-logic-switch-routing-demo
Conversation
@randomdevpete
@randomdevpeterandomdevpete
commented
Aug 21, 2026

Copy link


Copy Markdown

Owner
Summary
A deliberately minimal routing demo: one route atom holds which of a fixed set of pages the URL

names, a plain switch on its value picks the component to render, and the nav buttons navigate by

setting that atom instead of rendering <Link>s. It imports nothing from jarl-react — no Link,
Route or Switch component appears anywhere in SwitchRoutingApp.tsx.
The setRouteAtom question
The ticket left open whether to add a setRouteAtom primitive to jarl-atoms or approximate the

same shape with existing pieces. This PR approximates it: the fixed-set page segment is a
paramRouteAtom narrowed by a transformRouteAtom, the same composition numericRouteAtom's own

docstring calls "the usual way to build a constrained segment from the existing primitives". The

explicit generics on that transformRouteAtom call (<{ page: string }, { page: SwitchRoutingPage }>) are load-bearing: they pin the atom's value to the SwitchRoutingPage union rather than letting

it widen to string, which is what lets the switch in pageView be exhaustive with no default

case. Confirmed by typechecking the branch directly (tsc reports no errors on the new files, and the

same pre-existing, unrelated errors — missing @emotion/styled/highlight.js types, a generated
source-files.json — appear identically on the base branch).
No new export was added to jarl-atoms. setRouteAtom collides with jotai's own write vocabulary —

this demo already calls useSetAtom(pageRoute), and useSetAtom(setRouteAtom(...)) would fight

itself — and the base branch (#97) already composes constrained segments the same way, locally, for

its own demo (dateSegmentRouteAtom/filenameRouteAtom in ComplexRoutingApp.tsx, neither

exported).
Ticket 927 tracks a properly-named oneOfRouteAtom primitive for jarl-atoms, filed to land once

789 does.
Stack
Stacked on #97 (ticket 677), which this ticket depends on. Targets
task-677-complex-routing-demo-custom-path-atoms, not master.
@randomdevpete
feat(docs): 678 — routing demo that switches on a page route atom
b8adab4
A deliberately minimal demo: one route atom holds which of a fixed set of
pages the URL names, a plain `switch` on its value picks the component, and
the nav buttons navigate by writing that atom. It imports nothing from
`jarl-react` - no `Link`, `Route` or `Switch` component anywhere in it.
The fixed set is composed from existing exports rather than a new primitive:
a `paramRouteAtom` narrowed by a `transformRouteAtom`, the same composition
`numericRouteAtom` documents, which also types the value as the union the
switch needs so its cases are exhaustive.
Ticket: 678
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Already have an account?
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1 participant

@randomdevpete