# GTR036 — Replace deprecated `<output type="data">` (codemod)

**Contract:** behaviour-preserving.
## Claim
Renaming `<output type="data">` to `<data>` (dropping the attribute) is a
parse-level no-op.

## Proof
Galaxy routes an `<output type="data">` through the **same `_parse`** as
`<data>` (`tool_util/parser/xml.py:548-563`).

## Proof — the collection variant (ledger item C3, shipped)
The same routing block remaps the deprecated collection path in place —
`attrib["type"] = unicodify(collection_type)`, `attrib["type_source"] =
unicodify(collection_type_source)` — then parses via the same
`_parse_collection` as a `<collection>`. `unicodify(None)` is `None` (typed
overload, `util/__init__.py:1190-1196`), which reads identically to an absent
attribute, so when `collection_type` is present the static rewrite mirrors the
remap exactly.

## Scope boundary
`<output type="collection">` with **no** `collection_type` stays advisory — and
the degenerate case is now **verified broken** (2026-06-10): Galaxy's tree is
lxml (`galaxy.util` re-exports `from lxml import etree`,
`util/__init__.py:85`), so the deprecated path's
`attrib["type"] = unicodify(None)` raises `TypeError` at load — the tool never
worked. `<output>` with no `type` (an expression output — a different kind)
also stays advisory. Shipped at
~1-tool / ~0-tool corpus incidence — "not gated on corpus frequency" (the
ledger's precedent rule).