[venugopalanvip]

Two false positives in ValidateMaxLengthLinter, both the same shape: it measures a string that never reaches a screen against the limit for strings that do.

This matters here rather than only upstream because this is the library clear-signing-erc7730-registry installs for its validate descriptors job since ethereum/clear-signing-erc7730-registry#3008, so the noise lands on every contributor there.

1. A hidden label cannot be truncated

_collect_long_labels measured every label, including fields the device never draws:

$ erc7730 lint registry/p2p/calldata-P2pSsvProxyFactory.json
🟠 Display label too long: `Referrer Config Basis Points` exceeds 20 characters
   and may be truncated on Ledger devices.

That field is "visible": "never". Descriptors routinely spell out hidden struct leaves in full — it is how a reader tells #._referrerConfig.basisPoints from #._clientConfig.basisPoints.

rule	drawn?	measured?
always	yes	yes
optional	when the wallet can	yes
unset	yes	yes
ifNotIn	when the value is not in the list	yes
never	no	no
mustMatch	no — checked, not shown	no

mustMatch is worth spelling out: it is a constraint the device enforces without displaying the field, which is exactly why convert_erc7730_v2_input_to_calldata already lets such a field omit its label —

# A mustMatch field is never displayed, so the descriptor is allowed to omit its label, but
# the FIELD struct still requires a NAME tag.

A linter that permits no label while warning about a long one contradicts the converter.

2. {path} is template syntax, not displayed text

interpolatedIntent was measured as written, so the braces and the path inside them counted toward the 30-character limit. Neither is displayed, and the length of the value replacing them is not knowable here — an amount may render as 1 ETH or as eighteen decimal places.

The clearest case in the registry:

Swap {execution.desc.amount} for at least {execution.desc.minReturnAmount} to recipient {execution.desc.dstReceiver}

116 characters as written, 33 of literal text. {execution.desc.minReturnAmount} alone is 32 characters of path that never reaches a device.

Measured across the registry, at 0fbe25b

	count
long labels on hidden fields — cannot truncate	83
long labels on visible fields — all still reported	24
interpolatedIntent over 30 as written	111
— of those, placeholder text only	87
— genuinely too long, all still reported	24

So 170 of the 218 warnings in this family are about characters that never reach a device, and all 48 real ones survive.

Only the literal text is certain to reach the screen, so that is what is measured now. Over the limit on that alone means the intent truncates whatever the values render to — conservative, and it keeps every genuine case.

Scope and tests

Both remain warnings; nothing changes an exit code. Neither touches intent, id, metadata or enum lengths, which are literal strings and were always measured correctly.

tests/v2/lint/test_lint_validate_max_length.py is new: all six visibility rules, a ResolvedFieldGroup case proving a hidden child does not hide its visible sibling's label, and the literal-length measure including a 32-character path inside a placeholder and a literal that is genuinely over.

Also raised upstream as LedgerHQ/python-erc7730#341, unreviewed. Sending it here too since this is the copy the registry runs.