go-ldd v2.10.1: R2/R11 absence is a value (Introduce Null Object for optional collaborators); eval docs

[buzzdan]

Summary

Releases go-linter-driven-development 2.10.1. Motivated by the go-2.10.0-5828c34 eval baseline (buzzdan/ldd-evals#1).

R2 and R11: absence is a value

Both nil-handling reviews in the baseline (case-e-nils-review, 0/2) proposed "reject nil in the constructor" for an optional event sink and never offered the Null Object, and the refactor (case-e-nils-refactor, 0/1) introduced a one-implementation Sink interface to get a no-op, failing the R6 postcheck. The cause is structural: a hunter sees one rule file, and R2's fix list had no move for an optional collaborator. The Null Object lived only in R11, which pointed at R2 without R2 pointing back.

• core/rules/R2-self-validating-types.md: a new design point, "Absence is a value too", with the Reporter/DiscardSink() shape, and an Introduce Null Object fix move that names the fork: a required collaborator is rejected in the constructor; an optional one (logger, sink, clock, metrics) gets a do-nothing value by default, and every guard in the methods is deleted. "Hoist method checks" now says it is the wrong move for an optional field.
• lang/go/rules/R2/falsifying-questions.md: Q2 (methods re-checking fields) and Q6 (nil passed as an argument) carry the same fork, and ask the hunter to name both moves when the code does not say which the field is.
• core/rules/R11-conditional-dispatch.md: the Null Object entry states the Go shape. A no-op implementation only when an interface already exists; otherwise a value of the concrete type composing io.Discard (the standard library's own Null Object: a real io.Writer whose Write returns len(p), nil); never a new interface for the sake of the no-op (R6). Optional collaborators only.

Expected effect on the baseline: case-e-nils-review fix-null-object (0/2 today), and the refactor's nil-unrepresentable, default-constructor-exists and the R6 Q1 postcheck (0/1 in both medium passes). About $3 for the review case and $3 for the refactor to re-run.

Release 2.10.1

The changelog's Unreleased entries (this change, the generated plugin directory from #27, the behavioral evals) become ## [2.10.1] - 2026-09-11; plugin.json and the root README table follow. The plugin directory is regenerated; task check, lint-core (Residue table refreshed) and the docs gate pass.

Eval docs

• docs/eval-fixture.md describes the two grader-generator changes in buzzdan/ldd-evals#2: cluster graders match the word "cluster" followed by the anchor or its last dotted segment, and a plant may carry recall_match.
• docs/eval-harness.md and docs/eval-baseline.md name go-2.10.0-5828c34 as the current baseline, with its pass rates and the noise floor from two medium passes; 681fdb0 stays as the worked example of the comparison procedure.

🤖 Generated with Claude Code

https://claude.ai/code/session_01WrQTEgY87C1UdfgejismGr