iiinova — where your digital self keeps evolving

For a library, the source code isn’t the final artifact. The packed npm package is. That became very obvious during my tsup → tsdown migration, so I tested the actual tarball in temporary ESM, CJS, and TypeScript consumers. Full write-up tomorrow. 🔧 #TypeScript #OpenSource

020

nyaomaru @nyaomaru-dev.bsky.social · 19h

Yeah, they look super weird at first 😹 .d.mts and .d.cts are basically declaration-file versions of .mts / .cts, so the module format is explicit. It makes sense technically, it just didn’t match the filenames my package had already published. 😸

000

nyaomaru @nyaomaru-dev.bsky.social · 05/10/2026

A small tsup → tsdown migration surprise. Before: index.mjs index.js index.d.ts First tsdown build: index.mjs index.cjs index.d.mts index.d.cts The build passed. Nothing was “wrong” with tsdown, but reasonable new defaults can still break an existing package contract. 👀 #TypeScript #OpenSource

130

nyaomaru @nyaomaru-dev.bsky.social · 04/10/2026

What if AI didn’t write the “Why” in a CHANGELOG at all? In changelog-bot v0.7.0, Jev can select rationale already present in the PR description instead of generating new prose. Less invention. More grounding. Still experimental, but I like the direction. 👀 #OpenSource #AI #DevTools

010

nyaomaru @nyaomaru-dev.bsky.social · 03/10/2026

A green build doesn’t always mean a safe release. 👀 I migrated a real TypeScript OSS library from tsup to tsdown. The config change was tiny. The build passed. But the generated package no longer matched its existing contract. Full write-up Wednesday. 🔧 #TypeScript #OpenSource #tsdown

120

nyaomaru @nyaomaru-dev.bsky.social · 02/10/2026

Yes, I test the parent failure path separately. In fact, one test verifies that when the outer parent guard fails, refineKey doesn’t even read the child property. The parent establishes the shape first, then the child refinement runs inside that boundary. 😸

100

nyaomaru @nyaomaru-dev.bsky.social · 02/10/2026

changelog-bot v0.7.0 🚀 Experimental TypeSafe Jev support for WHY extraction is here. It selects rationale in PR descriptions instead of generating prose. Huge thanks to github.com/johnnylemonny! 🙌 github.com/nyaomaru/cha... #OpenSource #TypeScript #CHANGELOG #DevTools

github.com

Release v0.7.0 · nyaomaru/changelog-bot

What's new 🚀 v0.7.0 introduces experimental TypeSafe Jev support for WHY extraction. Jev is an opt-in WHY-only engine that performs confidence-aware candidate selection instead of generating new pr...

040

nyaomaru @nyaomaru-dev.bsky.social · 02/10/2026

Exactly! The child expression can be narrowed, but that doesn’t remove the uncertainty from the surrounding Node. That’s why the `isX` checks still matter for codemods when the API remains open. 😸

100

nyaomaru @nyaomaru-dev.bsky.social · 01/10/2026

Reusable AST guards can lose child-property narrowing. With is-kit, I compose existing ts.isX guards with a generic refineKey() helper while preserving parent + child narrowing. 🔧 dev.to/nyaomaru/typ...

dev.to

TypeScript Compiler API: Preserving Child Node Narrowing in Reusable Type Guards 🔧

Hoi hoi! 👋 I'm @nyaomaru, a frontend engineer exploring new possibilities with Jev 😸 (I'm also...

030

nyaomaru @nyaomaru-dev.bsky.social · 30/09/2026

I wrote new article! 🔧 Reusable parent + child narrowing gets awkward in the TypeScript Compiler API. I explored property refinement with `is-kit` and what changes in TypeScript 7. dev.to/nyaomaru/typ... #TypeScript #OpenSource

dev.to

TypeScript Compiler API: Preserving Child Node Narrowing in Reusable Type Guards 🔧

Hoi hoi! 👋 I'm @nyaomaru, a frontend engineer exploring new possibilities with Jev 😸 (I'm also...

030

nyaomaru @nyaomaru-dev.bsky.social · 30/09/2026

Yeah, that makes sense 😹 A giant closed union for every AST node would probably be expensive for the checker.

001

nyaomaru @nyaomaru-dev.bsky.social · 30/09/2026

Exactly 😹 This is a perfect example of where “automatic narrowing” still stops short. If node.kind doesn’t narrow the parent Node itself, codemod authors are still reaching for isX guards for another round.

100

nyaomaru @nyaomaru-dev.bsky.social · 29/09/2026

TypeScript 7 changed the Compiler API surface, but one thing surprised me: a broad `ast.Node` still isn’t a closed discriminated union. So `kind === CallExpression` doesn’t replace `isX` narrowing for that input. Full write-up tomorrow. 🔧 #TypeScript #CompilerAPI

250

nyaomaru @nyaomaru-dev.bsky.social · 29/09/2026

🎉 Changelog Bot is now live in GitBot’s in-app Library! You can now discover and use @nyaomaru/changelog-bot directly from GitBot 😸 Huge thanks to Sahil and the GitBot team for adding it! gitbot.codeongrass.com/bots/changelog-bot #OpenSource #DevTools

gitbot.codeongrass.com

Changelog Bot · GitBot Library

Previews release changelogs before updating the configured changelog.

020

nyaomaru @nyaomaru-dev.bsky.social · 28/09/2026

What does `arguments[0]` actually prove? Nothing, if the array is empty. A reusable guard for the first argument needs to prove: 1. index 0 exists 2. the value matches 3. the parent type remembers both facts Tiny runtime check, surprisingly interesting type problem. #TypeScript

030

nyaomaru @nyaomaru-dev.bsky.social · 27/09/2026

is-kit v1.15.0 is out! 🚀 A discussion about type-guard drift led to `discriminatedUnion`. It checks union coverage at compile time, so missing, extra, or mismatched branches can’t silently slip through. 👀 github.com/nyaomaru/is-... #TypeScript #OpenSource #is-kit

github.com

Release v1.15.0 · nyaomaru/is-kit

What's new 🚀 Exhaustively validate discriminated unions discriminatedUnion creates one type guard from a finite discriminated union. It requires every discriminant value in both the values tuple an...

020

nyaomaru @nyaomaru-dev.bsky.social · 27/09/2026

Optional AST children hide a different problem. `initializer?: Expression` isn’t just “another property to narrow.” A reusable guard must first prove that the property exists, then refine its value. That runtime contract deserves to be explicit. #TypeScript #OpenSource

020

nyaomaru @nyaomaru-dev.bsky.social · 26/09/2026

TypeScript 5.5 added inferred type predicates, which is great. But a compound check like: `CallExpression → expression → Identifier` can still end up as plain `boolean` when extracted. So where exactly does reusable narrowing stop being “free”? 👀 #TypeScript

020

nyaomaru @nyaomaru-dev.bsky.social · 25/09/2026

A type guard can prove both the parent and a child property at runtime. But if you extract the check into a reusable function, does TypeScript preserve both facts? `CallExpression → expression → Identifier` That small question turned into a bigger TypeScript rabbit hole. 😸 #TypeScript #WebDev

030

nyaomaru @nyaomaru-dev.bsky.social · 24/09/2026

A thought from writing this article 😸 A stale type guard can accept bad data, and the bug may appear much later far from the boundary that let it through. 👀 That distance is what makes silent drift painful. dev.to/nyaomaru/you... #TypeScript #OpenSource #OSS

dev.to

Your Type Guard Can Silently Drift from Your TypeScript Type 🔧

Hoi hoi! 👋 I'm @nyaomaru, a frontend engineer just back from a short vacation on Texel, a small...

030

nyaomaru @nyaomaru-dev.bsky.social · 23/09/2026

TypeScript article! 🔧 A handwritten type guard can stay valid while runtime checks fall behind the type. Why this drift happens, and how `typedStruct<User>()` catches it. 👀 dev.to/nyaomaru/you... #TypeScript #OpenSource

dev.to

Your Type Guard Can Silently Drift from Your TypeScript Type 🔧

Hoi hoi! 👋 I'm @nyaomaru, a frontend engineer just back from a short vacation on Texel, a small...

030

nyaomaru @nyaomaru-dev.bsky.social · 22/09/2026

This week I’ve been sharing one TypeScript maintenance problem: A hand-written type guard can keep compiling even after the type it claims to validate has changed. Tomorrow I’ll publish the full write-up — including drift, optional fields, nested types, and where `typedStruct` fits. 🔧 #TypeScript

010

nyaomaru @nyaomaru-dev.bsky.social · 21/09/2026

A small runtime-validation detail I like nickname?: string | null actually contains two separate contracts. The key may be absent. And if it exists, the value may be `null`. That’s why I prefer keeping key-level optionality and value-level nullability explicit. 👀 #TypeScript #OpenSource

050

nyaomaru @nyaomaru-dev.bsky.social · 20/09/2026

What if the existing TypeScript type could act as a compile-time contract for your runtime guard? That’s what I wanted from `typedStruct<User>()`. The runtime checks are still explicit, but missing or incompatible fields become TypeScript errors instead of silent drift. 👀 #TypeScript #OpenSource

030

nyaomaru @nyaomaru-dev.bsky.social · 19/09/2026

Yesterday I mentioned that `value is User` is a promise, not proof. Here’s the maintenance bug that follows: Add a field to `User`, forget to update the hand-written guard, and TypeScript can still compile. 👀 The type evolved. The runtime validation quietly stayed behind. #TypeScript

010

nyaomaru @nyaomaru-dev.bsky.social · 18/09/2026

TypeScript type guard finding 👀 A return type like: `value is User` is a promise made by the function — not proof that the runtime implementation actually checks every field. That gap can quietly become a maintenance problem. #TypeScript #JavaScript

010

nyaomaru @nyaomaru-dev.bsky.social · 17/09/2026

There’s a TypeScript side to `filter(Boolean)` too. 👀 It removes falsy values at runtime, but `Boolean` isn’t a type guard. So TypeScript doesn’t generally know that `null` and `undefined` are gone. More in my latest article 👇 dev.to/nyaomaru/why... #TypeScript #JavaScript #OpenSource

030

nyaomaru @nyaomaru-dev.bsky.social · 16/09/2026

`filter(Boolean)` looks nice — until `0`, `false`, or `""` quietly disappears. 🙀 Falsy ≠ Nullish. I wrote about TypeScript narrowing, `isNotNil`, and ESLint. 😸🔧 dev.to/nyaomaru/why... #TypeScript #JavaScript #OpenSource

dev.to

Why filter(Boolean) Is Not a Nullish Filter in TypeScript 🔧

Hoi hoi! 👋 I'm @nyaomaru, a frontend engineer building small TypeScript OSS with shoyu ramen....

030

nyaomaru @nyaomaru-dev.bsky.social · 15/09/2026

My post was featured in DEV Community’s Top 7 Posts of the Week! 😸🎉 Really happy to see it picked up by the DEV team. Thanks to everyone who read, reacted, and commented! ❤️‍🔥 dev.to/devteam/top-...

dev.to

Top 7 Featured DEV Posts of the Week

Welcome to this week's Top 7, where the DEV editorial team handpicks their favorite posts from the...

110

nyaomaru @nyaomaru-dev.bsky.social · 14/09/2026

Tiny JavaScript edge case 👀 `value != null` is often used as a short nullish check. But `document.all` is a historical browser exception: it behaves as nullish under loose equality. JavaScript is fun. 😹 #JavaScript #WebDev

000

nyaomaru @nyaomaru-dev.bsky.social · 12/09/2026

There’s a TypeScript side to `filter(Boolean)` too. 👀 It removes falsy values at runtime, but `Boolean` itself isn’t a type guard. So TypeScript doesn’t generally narrow away `null` and `undefined` just because the runtime filter does. #TypeScript

010

nyaomaru @nyaomaru-dev.bsky.social · 11/09/2026

Small JavaScript reminder 👀 `filter(Boolean)` means “keep truthy values,” not “remove only null and undefined.” So valid values like `0`, `false`, and `""` disappear too. Falsy and missing are different requirements. #JavaScript #TypeScript

040

nyaomaru @nyaomaru-dev.bsky.social · 10/09/2026

One thing I noticed while learning DSA: Very different algorithms can be difficult for the same reason, too much changing state to keep in your head. 👀 🌧️ Two pointers moving 🔢 Data changing from Map → buckets 👉 A sorted area growing step by step dev.to/nyaomaru/lea... #DSA #OpenSource

dev.to

Learn Trapping Rain Water, Top K Frequent and Selection Sort with Step-by-Step Visualization in DSA View View 👀👀

Hoi hoi! I’m @nyaomaru, a frontend engineer who has been obsessed with ramen lately. 😸🍜 Have you...

020

nyaomaru @nyaomaru-dev.bsky.social · 09/09/2026

New DSA View View article! 👀👀 🌧️ Trapping Rain Water → Two Pointers 🔢 Top K Frequent → Buckets 👉 Selection Sort → Selection Watch the runtime state change step by step. 😸 dev.to/nyaomaru/lea... #DSA #TypeScript #OpenSource

dev.to

Learn Trapping Rain Water, Top K Frequent and Selection Sort with Step-by-Step Visualization in DSA View View 👀👀

Hoi hoi! I’m @nyaomaru, a frontend engineer who has been obsessed with ramen lately. 😸🍜 Have you...

030

nyaomaru @nyaomaru-dev.bsky.social · 08/09/2026

is-kit v1.14.1 is out 😸 This release fixes two non-obvious runtime paths • preserves strict nullish semantics in browsers, including the document.all edge case • removes exception-driven checks from the successful isTypedArray path github.com/nyaomaru/is-... #TypeScript #OpenSource

github.com

Release v1.14.1 · nyaomaru/is-kit

What's Changed docs(changelog): 1.14.0 by @github-actions[bot] in #288 docs: validate hey-api types by @nyaomaru in #289 docs: clarify TypeScript 7 Compiler API compatibility by @nyaomaru in #290 ...

130

nyaomaru @nyaomaru-dev.bsky.social · 07/09/2026

I thought I’d found a TypeScript Compiler API gap. Then I reproduced it with plain objects. 👀 Turns out it’s a generic property-refinement composition problem. is-kit preserves the checked parent + child refinement for reuse without a manual return annotation. #TypeScript #OpenSource

050

nyaomaru @nyaomaru-dev.bsky.social · 06/09/2026

TypeScript inference finding 👀 Inline checks narrow correctly, but extracted predicates can fall back to `=> boolean`, losing child refinement on reuse. is-kit keeps it with `and()` + `refineKey()`. #TypeScript #OpenSource #CleanCode #TypeGuard

040

nyaomaru @nyaomaru-dev.bsky.social · 05/09/2026

TS7 AST finding 👀 Tested on TS 7.0.2 + a pinned 7.1 nightly: The shipped broad `Node` / `Expression` types still don’t narrow as discriminated unions through direct `kind` checks. is-kit keeps a reusable parent-child guard typed, without a manual parent intersection. #TypeScript #OpenSource

030

nyaomaru @nyaomaru-dev.bsky.social · 05/09/2026

Exactly! I see schema libraries and type guards as solving different problems. 😸 If a type guard is enough, I don’t think there’s any need to reach for a schema library.

000

nyaomaru @nyaomaru-dev.bsky.social · 03/09/2026

Thank you so much for all the kind words!! 😺✨ Your message really encouraged me, and it made me very happy! I’ll keep creating, coding, and sharing every day. 😸 Let’s keep going and do our best together! 💪

010

nyaomaru @nyaomaru-dev.bsky.social · 02/09/2026

Thank you! 😺 Actually, almost all of the pixel art is hand-drawn! 👀✨ I'm really happy you like the green and the cats too! 🐱💚

010

nyaomaru @nyaomaru-dev.bsky.social · 02/09/2026

I published another DSA View View article! 😸👀 This time: 🏝️ Number of Islands → DFS 🌳 Invert Binary Tree → Recursion 📚 Course Schedule → Topological Sorting The final code can be short, but the changing state is not always easy to follow. Let’s view it! 👀 dev.to/nyaomaru/lea... #DSA #OpenSource

dev.to

Learn Number of Islands, Invert Binary Tree, and Course Schedule with Step-by-Step Visualization in DSA View View 👀👀

Hoi hoi! I’m @nyaomaru, a frontend engineer who is surprised by how cold it is in the Netherlands...

130

nyaomaru @nyaomaru-dev.bsky.social · 02/09/2026

This gives me a much better direction for the next round of research. I really appreciate you taking the time to share all of this, it genuinely makes me happy to get this kind of feedback! 😸🙏

010

nyaomaru @nyaomaru-dev.bsky.social · 02/09/2026

Before deciding how is-kit should fit into that world, I’m going to take a closer look at the actual TypeScript 7 API and compare where native narrowing is already enough versus where reusable composition still has gaps.

120

nyaomaru @nyaomaru-dev.bsky.social · 02/09/2026

Thank you so much! 😺 This is a really valuable point. I had mostly been looking at existing narrowing patterns through a TypeScript 6 lens, but TypeScript 7 may change that landscape quite a bit, especially around AST types, kind narrowing, and the role of the existing isX helpers.

120