codecov.yml

# Codecov configuration — #923.
#
# Before this file there was NO codecov config anywhere in the repo, so
# `codecov/patch` ran on codecov's defaults (patch target `auto`: changed lines
# must meet the project average). Nobody chose that. It failed on essentially
# every PR and was treated as advisory for dozens of merges.
#
# That habit is not free. It is the same reflex that once let a red **Clippy**
# through as "just codecov" (#683, main went red). A check everyone is trained
# to ignore is worse than no check, so the choice here is to state the intent in
# config rather than leave it inferred from merge habits.
#
# ---------------------------------------------------------------------------
# WHAT WAS MEASURED FIRST (#923 step 1), and how it changed the plan
# ---------------------------------------------------------------------------
# `cargo llvm-cov --workspace` (CI's exclusion set), classified per file by
# whether an out-of-process EXECUTION oracle asserts it:
#
#     class          lines    instrumented-covered
#     differential   50238    86.2 %
#     unit-only      47754    83.4 %
#     TOTAL          97992    84.8 %
#
# The hypothesis in #923 was that differential-covered files are dragged down
# because `cargo llvm-cov` instruments the Rust suite IN-PROCESS while the
# differentials spawn `synth` as a separate, uninstrumented process. **At the
# aggregate that is not what the data shows** — differential-asserted files read
# slightly HIGHER (86.2 %) than unit-only ones (83.4 %). The effect is real
# per-file (`synth-backend-aarch64/src/backend.rs`: 267 lines, 44.2 %, exercised
# end-to-end constantly) but it does not dominate, and 6945 uncovered lines sit
# in differential-asserted files.
#
# The measurement also named the real target, which is NOT what was expected:
# `synth-verify/src/arm_semantics.rs` — 2481 lines at 47.4 %, unit-only, the
# largest single genuine gap in the workspace. Tests there would add evidence;
# tests written to lift the aarch64 backend's number would not.
#
# ---------------------------------------------------------------------------
# THE THRESHOLDS, and why these numbers
# ---------------------------------------------------------------------------
coverage:
  status:
    project:
      default:
        # Measured 84.8 % at v0.56. 80 % is a floor chosen to be met today with
        # real headroom, so a red `project` means coverage genuinely FELL rather
        # than "a PR touched an awkward file". Raise it when the arm_semantics.rs
        # gap closes; the ratchet direction is up.
        target: 80%
        threshold: 1%
        informational: false

    patch:
      default:
        # EXPLICITLY informational, not de-facto.
        #
        # This is the honest encoding of how it is already used, and it is not a
        # surrender: a patch status cannot distinguish "these changed lines are
        # untested" from "these changed lines are asserted by an execution
        # differential the instrument cannot see". Until the differentials emit
        # profile data (VG-009), a blocking patch gate reports a number it has
        # no way to make true.
        #
        # It still POSTS, so the signal stays visible on the PR — it just does
        # not pretend to be a gate. `project` above is the one that blocks.
        informational: true

comment:
  layout: "reach, diff, flags, files"
  behavior: default
  require_changes: false