Marey.Toolchain 0.7.0

Marey.Toolchain

External-program resolution and invocation for Marey, a dimensionally-typed visualization system for F#. A tool is resolved and reported, or it is absent and the absence names what to install.

#r "nuget: Marey.Toolchain"

open Marey

let ffmpeg = Toolchain.resolve "ffmpeg, from your package manager" "ffmpeg"

printfn "%s" (Toolchain.report "nothing was encoded" ffmpeg)

match Toolchain.runArgs ffmpeg [ "-version" ] "." 20_000 with
| ToolRan run -> printfn "%d: %s" run.ExitCode run.Out
| ToolUnavailable why -> printfn "%s" why
| ToolTimedOut why -> printfn "%s" why

Marey drives programs it does not ship — pdflatex for the TikZ goldens, pdftoppm for the ink gate, ffmpeg for video. This is the one place that answers "is it there?", and the wording of "it is not installed" is part of what it implements. It exists because that question had been answered five times in four files, in three different registers, and a reader had to know which one printed which.

Zero dependencies, deliberately. The packages that consume this already drag a toolchain each; the module that reports their absence must not be a third thing to install.

What is in it

• Toolchain.onPath — a hand-rolled PATH walk rather than a shell-out to where/which, because those are themselves external tools and their absence would be reported as the absence of the thing being looked for.

• ResolvedTool, carrying the install sentence rather than deriving it: the right thing to say differs per tool and per platform.

• Toolchain.run / runArgs, which capture both streams and drain them concurrently — reading one to the end and then the other deadlocks as soon as the child fills the second pipe's buffer, which is to say on the run that finally had enough errors to be worth reading. Prefer runArgs whenever an argument is a path: ProcessStartInfo.Arguments is re-split using Windows' quoting rules on every platform, and a vector needs no quoting.

• ToolOutcome, three cases and not a Result: "not installed", "timed out" and "ran and exited" call for different behaviour at every call site, and collapsing them is how a gate goes quietly vacuous.

• The repository