EnsembleKalmanProcesses.jl: Skill for Claude Code

base-show

Add concise Base.show(io::IO, ::MIME"text/plain", x::T) and Base.summary(io::IO, x::T) methods to Julia types whose default REPL representation is unhelpful or overwhelming. Julia's default show dumps every field recursively; types that hold DataFrames, large dictionaries, nested arrays, or many scalar fields produce screens of unreadable text at the REPL.

Base.show(io, MIME"text/plain", x) must also handle the :compact IOContext key. When Julia renders an object as an element inside a container (e.g. printing a Vector{MyType}), it sets :compact => true on io. Without a compact branch the full multi-line output is repeated for every element, producing an unreadable wall of text. The compact branch must produce exactly one line (no newlines), giving the same kind of at-a-glance hint as Base.summary.

This skill produces both methods and accompanying unit tests so that interactive use of the package is pleasant without losing key summary information.

Workflow

Step 0 — Audit existing show methods (retrofit mode)

Skip this step if you are adding show methods to types that have none. Apply it when the user asks to retrofit existing show methods — e.g. to add the compact branch to methods that were written before this protocol existed.

Find MIME methods that lack the compact branch:

grep -n 'MIME"text/plain"' src/show.jl

For each match, check whether the function body contains get(io, :compact. Any that do not are candidates for retrofit.

Detect the old forwarding anti-pattern (infinite-recursion risk):

grep -nA2 'function Base\.show(io::IO, x::' src/ | grep 'show(io, MIME'

If this matches, a 2-arg show(io, x) is calling the MIME method — the wrong direction. Once the MIME method gains a compact branch that calls show(io, x), you get infinite recursion. Flag every match and reverse the direction: the 2-arg method becomes the compact one-liner, and the MIME method calls it via show(io, x) in its compact branch.