# GTR004 — Empty-element shorthand (fmt)

**Contract:** behaviour-preserving.
## Claim
Collapsing a whitespace-only leaf to `<foo/>` is a no-op.

## Proof
- For an element-only/empty content model, ws-only `.text` is layout (the
  GTR003 spec clause).
- The rule **skips every schema-text-bearing element** (the derived payload
  guard, fmt §D20 — `schema_content.text_bearing_tags()` across all 28 XSDs):
  a ws-only body there may be verbatim payload (Galaxy reads
  `<command>`/`<configfile>`/`<token>` with `strip=False`).
- **Context collision, derivation-surfaced:** `<inputs>` is element-only under
  `<tool>` but `simpleContent` under `<configfiles>` (`ConfigInputs`) — payload
  only in the configfiles context (parent-tag check).

## Proof-carried exceptions (still collapsed)
- `<help>`: a whitespace-only help renders empty either way (fmt D18).
- `<macros>` (legacy `xs:anyType`): Galaxy's loader harvests children then
  **clears the element** (`galaxy/util/xml_macros.py:39-45`) — its text is dead.

## History
Refuted (content-bearing leaves) → denylist PR #113 → schema derivation fmt
§D20 (found the configfiles-`<inputs>` latent case).