assertgen

internal/gen/assertgen

Code generator that emits partial-match assertion structs for every exported struct type in a list of Go packages.

What it produces

For each exported, non-List, non-Status struct it finds, the generator emits:

// XxxAssertion is the assertion struct for Xxx.
type XxxAssertion struct {
	FieldA Opt[string]                  // scalar
	FieldB OtherAssertion               // nested Assertable
	FieldC Opt[[]OtherAssertion]        // slice of Assertable
	FieldD Opt[map[string]string]       // map (subset match)
}

// IsAssertable marks XxxAssertion as an Assertable.
func (_ XxxAssertion) IsAssertable() {}

Field shape:

• Type is a known struct (from one of the scanned packages) → nested OtherAssertion.
• Type is []KnownStruct → Opt[[]OtherAssertion].
• Anything else → Opt[T].

The Opt[T], Assertable, and Partial machinery is hand-written and lives in ../../../assert — the generator only emits the struct catalogue.

Invocation

go run github.com/mridang/wilhelm/internal/gen/assertgen \
  -out zz_generated.go \
  -package assert \
  [-packages a.b/x/v1,a.b/y/v1]

Without -packages, the generator scans the same set zitadel-charts used (core K8s API groups + Gateway API + Prometheus Operator). The flag lets per-CRD subpackages target only their own upstream types so each generated file imports a minimum set of dependencies.

How go generate wires it up

assert/doc.go carries the directive:

//go:generate go run ../internal/gen/assertgen -out zz_generated.go -package assert

Each CRD subpackage gets its own doc.go-style file with -packages pointing at its target.

Disambiguation

The same struct name (Application, Cluster, Gateway, ...) can exist in multiple scanned packages. When that happens, the first occurrence keeps the short name XxxAssertion; collisions get prefixed with a package-derived word (e.g. MetaCluster, ArgoApplication).

Determinism

Output is sorted by pkgPath + "." + typeName so two runs of go generate in a clean checkout produce byte-identical output. CI uses this to check that committed generated files match the upstream API.