# Stacky ☆ BEAM stack trace in Gleam

**a stack trace of stack frames with module name, function name, arity, file name and line number**

[![Package
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![Erlang-compatible](https://img.shields.io/badge/target-erlang-b83998)

Best used with [pprint](https://hexdocs.pm/pprint/).

```shell
gleam add stacky
gleam add pprint
```

## Usage

```gleam
import pprint
import stacky

pub fn main() {
  let stack =
    stacky.trace()
    // See the strack trace:
    |> pprint.debug

  let frame =
    stack
    |> stacky.frame(0)
    // See the top most stack frame, from this call site:
    |> pprint.debug

  frame
  |> stacky.gleam_module_name
  // See the current module name, from this call site:
  |> pprint.debug

  frame
  |> stacky.function_name
  // See the current function name, from this call site:
  |> pprint.debug

  // prints gleam module.function and erlang with line number to stdout
  frame |> stacky.print_frame_ln
}
```

`stdout`:

```gleam
StackTrace([
  StackFrame(
    ErlangModuleName("stacky"),
    FunctionName("main"),
    FunctionArity(0),
    ErlangFileName("stacky/build/dev/erlang/stacky/_gleam_artefacts/stacky.erl"),
    ErlangLineNumber(202),
  ),
  StackFrame(
    ErlangModuleName("stacky@@main"),
    FunctionName("run"),
    FunctionArity(1),
    ErlangFileName("stacky/build/dev/erlang/stacky/_gleam_artefacts/stacky@@main.erl"),
    ErlangLineNumber(11),
  ),
  StackFrame(
    ErlangModuleName("erl_eval"),
    FunctionName("do_apply"),
    FunctionArity(7),
    ErlangFileName("erl_eval.erl"),
    ErlangLineNumber(746),
  ),
  StackFrame(
    ErlangModuleName("init"),
    FunctionName("start_it"),
    FunctionArity(1),
    ErlangFileName("not-a-file"),
    ErlangLineNumber(-1),
  ),
  StackFrame(
    ErlangModuleName("init"),
    FunctionName("start_em"),
    FunctionArity(1),
    ErlangFileName("not-a-file"),
    ErlangLineNumber(-1),
  ),
  StackFrame(
    ErlangModuleName("init"),
    FunctionName("do_boot"),
    FunctionArity(3),
    ErlangFileName("not-a-file"),
    ErlangLineNumber(-1),
  ),
])
StackFrame(
  ErlangModuleName("stacky"),
  FunctionName("main"),
  FunctionArity(0),
  ErlangFileName("stacky/build/dev/erlang/stacky/_gleam_artefacts/stacky.erl"),
  ErlangLineNumber(202),
)
```

```
"stacky"
```

```
"main"
```

```
stacky.main - arity: 0 - erlang file: stacky/build/dev/erlang/stacky/_gleam_artefacts/stacky.erl:202
```

## Demo

```shell
gleam run -m stacky/internal/sub_dir/example_in_sub_dir.gleam
```

Further documentation can be found at <https://hexdocs.pm/stacky>.