Async, Awaited

The Seagrape in Roatan

The folding keyboard from last week’s been scrapped, but I’m still writing on mobile platforms; this week from a less-exotic-but-more-expensive Apple Magic Keyboard. These weren’t designed with mobility in mind, but are surprisingly good at it: compact, good battery life, no butterfly keys. Their Achilles’ heel is that they need to be stored in a Ziplock bag lest their veneer of purest white become a muddied black faster than you say “One Infinite Loop”.

This is Nanoglyph, a software weekly, issue four. It’s an in-progress experiment in email-based publishing, disciplined writing, and independent communication less prone to the heavy gravity wells of social media. I’m not slinging it widely, but if you want to help with the prototype, you can subscribe here.

Today’s photo is from a recent dive trip to Honduras. More on that in soon-to-come edition of Passages & Glass (my other, less software oriented, much less frequent newsletter) if you’re interested in hearing more.

Last week, async-await stabilized in Rust. It was a long road to get there. It started early exploration into a variety of concurrency models, including Go-like green threads that were deliberated out in preference of an ultra-minimal runtime. Then came a terrible misadventure in using macros to build async-await as user-space abstractions. The result was agony, with any mistake producing compiler errors so inscrutable that even the darkest days of C++ templates looked good by comparison. Finally, what felt like the longest wait: today’s async/.await was proposed, implemented, and went through a lengthy vetting process before arriving at where it is today. It’s been almost two years since the original RFC.

These days, with so many of us building network-based programs like APIs and web applications, plausible concurrency is a critical hallmark of any modern language. With its asynchronous mechanics finally finished, in a practical sense this is Rust’s true beginning. Higher level constructs will come next, starting with a release of Tokio this month, and culminating with fast, efficiency, and refined web/network stacks. Exciting times lie ahead.

Russ Cox writes about software dependencies, a topic that’s infamously relevant to Go, and even more so him personally as one of the drivers of the new-ish Go Module system.

His premise is that although the steady advances in the quality and ease-of-use of package managers is a good thing, their use is now so streamlined that modern developers rarely hesitate before adding new dependencies. This is well exemplified well by Node’s escape-string-regexp package, an 8-line package in use by 1,000+ other Node packages and an untold numbers of apps.

Dependencies are tremendously useful for building features quickly, but have less obvious long term ramifications in maintenance, bugs, and security. A recent example was the introduction of malicious code into Node’s event-stream package to steal from the Bitcoin wallets of Copay users. An even greater sensation was the exfiltration of data of 146M Americans from Equifax, which turned out to be due to a vulnerability in Apache Struts.

The article suggests vetting dependencies before use by examining their design, code quality, state of maintenance, transitive dependencies, and security history. Depending on the results, you may decide to pick up the dependency, engage it more carefully through an isolation mechanism like a sandbox, or avoiding it. He notes that Apache Struts disclosed major remote code execution vulnerabilities in 2016, 2017, and 2018 – projects with such sordid histories might be best avoided altogether.

A point of interest is that Go is experimenting with including dependency version manifests in compiled binaries, which would allow tooling to scan them for liabilities that should prompt an upgrade. It’s a great idea given that the opaqueness of an already-compiled binary is one of the few downsides of deployment via static binary compared to alternatives.

An exciting development in Apple’s toolchain was the introduction of SwiftUI, their take on a React-like system for building declarative, modular UIs. And unlike React, allowing you to do so in the elegance of Swift instead of free form JSX syntactic sugar. By most reports using it today is rough going, but it looks promising.

Static types in SwiftUI describes how Swift infers complex types based on views built with the framework. So something like:

let stack = VStack {
        .fill(myState ? :
        .frame(width: 100, height: 100)

Is interpreted by the compiler as the nested, parameterized type VStack<TupleView<(Text, ModifiedContent<_ShapeView<Rectangle, Color>, _FrameLayout>)>>.

React-like frameworks re-render view trees as their encapsulated state changes. That typically involves a diff step, where old and new trees are compared so that the framework can determine if new elements need to be added or old ones removed. Having a static type to describe each view allows SwiftUI to minimize that work, or even skip it altogether — the type system tells it in advance that elements remain constant, and it’s just their internal state that needs updating.

But not all views are that simple. A more complex one might include a conditional that makes typing difficult:

if myState {

SwiftUI handles this case by replacing a required Text field with an optional Text? in the static type. Some tree diffing is now necessary, but only a minimal amount where conditional elements are present.

Full if ... else ... constructs are also supported by typing (they become _ConditionalContent<A, B>) and in cases where conditional logic becomes too complex to encode, the type-erased AnyView acts as a fall back to represent anything.

And speaking of, React may just be one of the most important software innovations of the decade.

When competing technologies are vetted in the field for years, there’s often no clear winner — Python and Ruby have both been around for a long time, and likely will be for years. Similarly, the JVM and .NET runtime. But that’s not always the case; sometimes after years of competition, one option gains enough momentum to become a de facto standard, and starts to look like a clear way forward. HTML5 and JS in their long battle against Flash and Silverlight for the future of web technology. Linux over Solaris. TypeScript over Flow. Postgres over MySQL. Nginx. None are absolutes, but there’s a clear answer for most people most of the time.

React’s in this bucket. It took decades to find this pattern for building sustainable UIs. Event handlers on UI elements and data binding were the gold standard for desktop development for most of that time. Later, patterns like MVP 1 were recommended. On the web, the right answer was piecemeal JavaScript with assists from jQuery before heavier frameworks like Angular, Amber, and React started to appear.

Time has shown that React’s particular brand of declarative syntax and decoupled state management is an excellent way to build maintainable UIs modular enough to scale well to even the largest development teams. It’s already adopted very widely, and still picking up steam. More importantly, its core premise is being reused by the likes of Elm and SwiftUI, projects that could very plausibly have gone the other way and invented their own — that’s the closest you’re likely to get to definitive proof that React sparked something truly enduring.

1Model-view-presenter, a derivation of model-view-controller (MVC).