This is an alternative, less intrusive take on D133943 (where we were unable to find consensus on how to handle updating existing in-tree tests). Zooming right out, the basic problem is that `--function-signature` checks arguments but now the return type. This limitation means it's not very useful for my use case (making RISC-V ABI tests more maintainable). The value of this is huge - manually updating CHECK lines in the previous ABI tests was a massive timesink, and with this feature it is _massively_ easier. Although it would be cleaner in a sense to update `--function-signature` and find agreement on transitioning in-tree tests to the new behaviour, I think adding the separate command-line flag is the best option available at this point. It's hopefully much easier to get this reviewed and landed, thus unblocking the ABI test refactorings and follow-on bug fixes that rely on it. There's also a clear migration path - in the future `--function-signature` could be updated to act like `--full-function-signature` and `--full-function-signature` be either removed or left as an alias. It would be slightly better to support `--function-signature=full`, but I couldn't find a way to accept an optional argument but only with `--foo=bar` syntax (rather than `--foo bar`, which could break existing command lines) with default argparse routines. I'd really, really, really appreciate help on unblocking this (reviews or other feedback). Thank you in advance.

This is an alternative, less intrusive take on D133943 (where we were unable to find consensus on how to handle updating existing in-tree tests). Zooming right out, the basic problem is that `--function-signature` checks arguments but not the return type. This limitation means it's not very useful for my use case (making RISC-V ABI tests more maintainable). The value of this is huge - manually updating CHECK lines in the previous ABI tests was a massive timesink, and with this feature it is _massively_ easier. Although it would be cleaner in a sense to update `--function-signature` and find agreement on transitioning in-tree tests to the new behaviour, I think adding the separate command-line flag is the best option available at this point. It's hopefully much easier to get this reviewed and landed, thus unblocking the ABI test refactorings and follow-on bug fixes that rely on it. There's also a clear migration path - in the future `--function-signature` could be updated to act like `--full-function-signature` and `--full-function-signature` be either removed or left as an alias. It would be slightly better to support `--function-signature=full`, but I couldn't find a way to accept an optional argument but only with `--foo=bar` syntax (rather than `--foo bar`, which could break existing command lines) with default argparse routines. I'd really, really, really appreciate help on unblocking this (reviews or other feedback). Thank you in advance.

This is an alternative, less intrusive take on D133943 (where we were unable to find consensus on how to handle updating existing in-tree tests). Zooming right out, the basic problem is that `--function-signature` checks arguments but nownot the return type. This limitation means it's not very useful for my use case (making RISC-V ABI tests more maintainable). The value of this is huge - manually updating CHECK lines in the previous ABI tests was a massive timesink, and with this feature it is _massively_ easier. Although it would be cleaner in a sense to update `--function-signature` and find agreement on transitioning in-tree tests to the new behaviour, I think adding the separate command-line flag is the best option available at this point. It's hopefully much easier to get this reviewed and landed, thus unblocking the ABI test refactorings and follow-on bug fixes that rely on it. There's also a clear migration path - in the future `--function-signature` could be updated to act like `--full-function-signature` and `--full-function-signature` be either removed or left as an alias. It would be slightly better to support `--function-signature=full`, but I couldn't find a way to accept an optional argument but only with `--foo=bar` syntax (rather than `--foo bar`, which could break existing command lines) with default argparse routines. I'd really, really, really appreciate help on unblocking this (reviews or other feedback). Thank you in advance.