130 lines
3.7 KiB
Markdown
130 lines
3.7 KiB
Markdown
# Pry debugging
|
|
|
|
## Invoking pry debugging
|
|
|
|
To invoke the debugger, place `binding.pry` somewhere in your
|
|
code. When the Ruby interpreter hits that code, execution will stop,
|
|
and you can type in commands to debug the state of the program
|
|
|
|
## `byebug` vs `binding.pry`
|
|
|
|
`byebug` has a very similar interface as `gdb`, but `byebug` does not
|
|
use the powerful Pry REPL.
|
|
|
|
`binding.pry` uses Pry, but lacks some of the `byebug`
|
|
features. GitLab uses the [`pry-byebug`](https://github.com/deivid-rodriguez/pry-byebug)
|
|
gem. This gem brings some capabilities `byebug` to `binding.pry`, so
|
|
using that, will give you the most debugging powers.
|
|
|
|
## `byebug`
|
|
|
|
Check out [the docs](https://github.com/deivid-rodriguez/byebug) for the full list of commands.
|
|
|
|
You can start the Pry REPL with the `pry` command.
|
|
|
|
## `pry`
|
|
|
|
There are **a lot** of features present in `pry`, too much to cover in
|
|
this document, so for the full documentation head over to the [Pry wiki](https://github.com/pry/pry/wiki).
|
|
|
|
Below are a few features definitely worth checking out, also run
|
|
`help` in a pry session to see what else you can do.
|
|
|
|
### State navigation
|
|
|
|
With the [state navigation](https://github.com/pry/pry/wiki/State-navigation)
|
|
you can move around in the code to discover methods and such:
|
|
|
|
```ruby
|
|
# Change context
|
|
[1] pry(main)> cd Pry
|
|
[2] pry(Pry):1>
|
|
|
|
# Print methods
|
|
[2] pry(Pry):1> ls -m
|
|
|
|
# Find a method
|
|
[3] pry(Pry):1> find-method to_yaml
|
|
```
|
|
|
|
### Source browsing
|
|
|
|
You [look at the source code](https://github.com/pry/pry/wiki/Source-browsing)
|
|
from your `pry` session:
|
|
|
|
```ruby
|
|
[1] pry(main)> $ Array#first
|
|
# The above is equivalent to
|
|
[2] pry(main)> cd Array
|
|
[3] pry(Array):1> show-source first
|
|
```
|
|
|
|
`$` is an alias for `show-source`.
|
|
|
|
### Documentation browsing
|
|
|
|
Similar to source browsing, is [Documentation browsing](https://github.com/pry/pry/wiki/Documentation-browsing).
|
|
|
|
```ruby
|
|
[1] pry(main)> show-doc Array#first
|
|
```
|
|
|
|
`?` is an alias for `show-doc`.
|
|
|
|
### Command history
|
|
|
|
With **Ctrl+R** you can search your [command history](https://github.com/pry/pry/wiki/History).
|
|
|
|
## Stepping
|
|
|
|
To step through the code, you can use the following commands:
|
|
|
|
- `break`: Manage breakpoints.
|
|
- `step`: Step execution into the next line or method. Takes an
|
|
optional numeric argument to step multiple times.
|
|
- `next`: Step over to the next line within the same frame. Also takes
|
|
an optional numeric argument to step multiple lines.
|
|
- `finish`: Execute until current stack frame returns.
|
|
- `continue`: Continue program execution and end the Pry session.
|
|
|
|
## Callstack navigation
|
|
|
|
You also can move around in the callstack with these commands:
|
|
|
|
- `backtrace`: Shows the current stack. You can use the numbers on the
|
|
left side with the frame command to navigate the stack.
|
|
- `up`: Moves the stack frame up. Takes an optional numeric argument
|
|
to move multiple frames.
|
|
- `down`: Moves the stack frame down. Takes an optional numeric
|
|
argument to move multiple frames.
|
|
- `frame <n>`: Moves to a specific frame. Called without arguments
|
|
will show the current frame.
|
|
|
|
## Short commands
|
|
|
|
When you use `binding.pry` instead of `byebug`, the short commands
|
|
like `s`, `n`, `f`, and `c` do not work. To reinstall them, add this
|
|
to `~/.pryrc`:
|
|
|
|
```ruby
|
|
if defined?(PryByebug)
|
|
Pry.commands.alias_command 's', 'step'
|
|
Pry.commands.alias_command 'n', 'next'
|
|
Pry.commands.alias_command 'f', 'finish'
|
|
Pry.commands.alias_command 'c', 'continue'
|
|
end
|
|
```
|
|
|
|
## Repeat last command
|
|
|
|
You can repeat the last command by just hitting the <kbd>Enter</kbd>
|
|
key (e.g., with `step` or`next`), if you place the following snippet
|
|
in your `~/.pryrc`:
|
|
|
|
```ruby
|
|
Pry::Commands.command /^$/, "repeat last command" do
|
|
_pry_.run_command Pry.history.to_a.last
|
|
end
|
|
```
|
|
|
|
`byebug` supports this out-of-the-box.
|