# Tztop

`tztop` is a customised top-level meant to assist Tezos protocol development with a REPL (an interactive Read-Eval-Print-Loop)


## Motivation
Toplevel environment needs `Stdlib`, but Tezos protocols are built with a restricted `Stdlib`.
To work around this, we let the `Persistent_env.Persistent_signature.load` fallback to the default load of `Stdlib` so that top-level can setup its initial environment.


## Usage

### Pre-requisites

If `.lambda-term-inputrc` doesn't exist, an empty one must be created.

```
touch ~/.config/.lambda-term-inputrc
```

### Command syntax

```
dune exec -- tztop DIR [options/flags recognised by uTop]
```

Runs toplevel with libraries defined in DIR and optional flags and args that follow.

### Example Usage

```
dune exec -- tztop src/proto_alpha/
```

If you're in an environment that doesn't have opam env hooks, 


```
opam exec -- dune exec -- tztop src/proto_alpha/
```

`tztop` also accepts flags and options accepted originally by the toplevel.

For instance, for stdin redirection:

```
echo "#show_module Tezos_protocol_alpha.Protocol" | dune exec -- tztop src/proto_alpha -stdin
```

Or, for editor integrations:

```
dune exec -- tztop DIR -emacs
```

See [Proposal Testing](https://tezos.gitlab.io/developer/proposal_testing.html)
page for a sample code to run in `tztop`.

## Troubleshooting

If `tztop` segfaults or throws an OCaml backtrace regarding missing rc files, consider creating empty `.utoprc` and `.lambda-term-inputrc` files in the `$XDG_CONFIG_HOME` directory:

```
mkdir -p $HOME/.config
touch $HOME/.config/.lambda-term-inputrc
touch $HOME/.utoprc
touch $HOME/.utop-history
```

On macOS the following command is required:

```
export DYLD_LIBRARY_PATH='_opam/lib/stublibs/'
```

Otherwise `tztop` fails with the following error:

```
Fatal error: cannot load shared library dllocamlevercrypt
Reason: dlopen(/Users/.../tezos/_opam/lib/stublibs/dllocamlevercrypt.so, 10): Library not loaded: libevercrypt.so
  Referenced from: /Users/.../tezos/_opam/lib/stublibs/dllocamlevercrypt.so
  Reason: image not found
Abort trap: 6
```

Also make sure that `utop` is installed (run `make build-dev-deps`).
Otherwise `tztop` fails with the following error:

```
Tztop failed to load due to an internal error
Unable to find directive load
```