Add showrepr battery for short Base.show

.github/workflows/CI.yml

@@ -23,6 +23,18 @@ jobs:
         with:
           version: ${{ matrix.version }}
           arch: ${{ matrix.arch }}
+      - name: Drop JET deps on Julia versions JET does not support
+        # JET requires 1.7 <= Julia <= 1.12, so Pkg cannot resolve
+        # JET on Julia 1.6 or on nightly. Strip JET from Project.toml
+        # (compat + extras + targets) and from runtests.jl on those
+        # rows so the rest of the test suite still runs green.
+        # The job using a registered JET-supported Julia version ('1')
+        # keeps full JET coverage.
+        if: matrix.version == 'nightly' || matrix.version == '1.6'
+        run: |
+          sed -i '/^JET = /d' Project.toml
+          sed -i 's/, "JET"//' Project.toml
+          sed -i '/^@testset "JET" begin$/,/^end$/d' test/runtests.jl
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
       - uses: julia-actions/julia-processcoverage@v1

Project.toml

@@ -9,6 +9,8 @@ ConstructionBase = "187b0558-2788-49d3-abe0-74a17ed4e7c9"
 [compat]
 Aqua = "0.8, 1"
 ConstructionBase = "1.3"
+JET = "0.9, 0.10, 0.11"
+StaticArrays = "1"
 StructTypes = "1"
 # `Test` is a stdlib. On Julia < 1.11 it is reported as unversioned
 # (matched by `<0.0.1`); on Julia >= 1.11 it has a real version (matched
@@ -19,8 +21,10 @@ julia = "1.6"
 
 [extras]
 Aqua = "4c88cf16-eb10-579e-8560-4a9242c79595"
+JET = "c3a54625-cd67-489e-a8e7-0a5a0ff4e31b"
+StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
 StructTypes = "856f2bd8-1eba-4b0a-8007-ebc267875bd4"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Aqua", "Test", "StructTypes"]
+test = ["Aqua", "JET", "StaticArrays", "StructTypes", "Test"]

README.md

@@ -77,6 +77,34 @@ For all supported options and defaults, consult the docstring:
 julia>?@batteries
 ```
 
+## `kwshow` vs `showrepr`
+
+Two options overload `Base.show`; pick at most one (passing both is an
+error):
+
+* `kwshow=true` always renders `T(f1 = v1, f2 = v2, …)` — every field,
+  named, in declaration order. The output shape is fixed and stable
+  across versions, which makes it well-suited to diagnostics and
+  golden-file tests. It round-trips through `eval` only when the type
+  has a keyword constructor (e.g. via `kwconstructor=true` or
+  `Base.@kwdef`).
+
+* `showrepr=true` prints a heuristically short constructor call that
+  recreates the object. It probes every constructor of the type
+  (positional, keyword, hybrid), omits trailing fields that already
+  match a default, and substitutes shorter literals where the
+  constructor still accepts them (e.g. `0x2a` → `42`, `2//1` → `2`,
+  uniform vectors → `fill(v, n)`). Because the result depends on the
+  field values and on the package's heuristics, the exact output is
+  *not* guaranteed to be stable across minor releases — don't pin
+  golden files against it. If no constructor recreates the object,
+  `showrepr` falls back to a non-executable `T(field = value, …)`
+  rendering.
+
+Rule of thumb: pick `kwshow` if you want a predictable, name-every-field
+diagnostic; pick `showrepr` if you want `Base.show` to produce an
+idiomatic, recreatable, as-short-as-reasonable form for end users.
+
 # Alternatives
 
 * [AutoHashEquals](https://github.com/andrewcooke/AutoHashEquals.jl) requires annotating the struct definition. This can be inconvenient if you want to annotate the definition with another macro as well.

src/StructHelpers.jl

@@ -7,6 +7,8 @@ export @enumbattery
 
 import ConstructionBase: getproperties, constructorof, setproperties
 
+include("showrepr.jl")
+
 # `$SH.foo` in macro emissions interpolates the StructHelpers module value
 # directly into the generated AST. This resolves via `getproperty` at the
 # call site without requiring `import StructHelpers` (or any caller-side
@@ -112,6 +114,16 @@ end
     nt = Tuple(getproperties(o))
     Base.hash(nt, h)
 end
+"""
+    kwshow(io::IO, o)
+
+Show `o` as `T(f1 = v1, f2 = v2, ...)`, listing every field as a keyword
+argument. The output is recreatable via the keyword constructor (see
+[`@batteries`](@ref) with `kwconstructor=true`).
+
+For a representation that picks the shortest constructor call and omits
+default values, see [`showrepr`](@ref).
+"""
 function kwshow(io::IO, o)
     print(io, typeof(o))
     print(io, "(")
@@ -173,6 +185,7 @@ const BATTERIES_DEFAULTS = (
     kwconstructor = false,
     selfconstructor = true,
     kwshow        = false,
+    showrepr      = false,
     getproperties = true ,
     constructorof = true ,
     typesalt      = nothing,
@@ -186,6 +199,7 @@ const BATTERIES_DOCSTRINGS = (
     kwconstructor = "Add a keyword constructor. Defaults can be supplied by overloading [`default_keywords`](@ref).",
     selfconstructor = "Add a constructor of the for `T(self::T) = self`",
     kwshow        = "Overload `Base.show` such that the names of each field are printed. Fields whose value is `isequal` to the value returned by [`default_keywords`](@ref) are omitted.",
+    showrepr      = "Overload `Base.show` to print a heuristically short constructor call that recreates the object, omitting default values. Mutually exclusive with `kwshow`.",
     getproperties = "Overload `ConstructionBase.getproperties`.",
     constructorof = "Overload `ConstructionBase.constructorof`.",
     typesalt      = "Only used if `hash=true`. In this case the `hash` will be purely computed from `typesalt` and `hash_eq_as(obj)`. The type `T` will not be used otherwise. This makes the hash more likely to stay constant, when executing on a different machine or julia version",
@@ -350,9 +364,7 @@ function def_batteries(__module__, T, kw, base)
     ret = quote end
 
     need_fieldnames = nt.kwconstructor || nt.getproperties
-    if need_fieldnames
-        fieldnames = Base.fieldnames(Base.eval(__module__, T))
-    end
+    fieldnames = need_fieldnames ? Base.fieldnames(Base.eval(__module__, T)) : ()
     need_StructTypes = nt.StructTypes
     if need_StructTypes
         push!(ret.args, :(import StructTypes as $ST))
@@ -380,10 +392,17 @@ function def_batteries(__module__, T, kw, base)
         )
         push!(ret.args, def)
     end
+    if nt.kwshow && nt.showrepr
+        error("`kwshow` and `showrepr` are mutually exclusive; please pick at most one.")
+    end
     if nt.kwshow
         def = :($(Base).show(io::$IO, o::$T) = $(kwshow)(io, o))
         push!(ret.args, def)
     end
+    if nt.showrepr
+        def = :(Base.show(io::IO, o::$T) = $(showrepr)(io, o))
+        push!(ret.args, def)
+    end
     if nt.getproperties
         def = def_getproperties(T, fieldnames)
         push!(ret.args, def)