[all-commits] [llvm/llvm-project] f1ddfa: [lldb] Remove pydoc import during script interpret...

[Dave Lee via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f1ddfa6d8a72bcc89e01ab8f73bbe5ae5a0dc475
      https://github.com/llvm/llvm-project/commit/f1ddfa6d8a72bcc89e01ab8f73bbe5ae5a0dc475
  Author: Dave Lee <davelee.com at gmail.com>
  Date:   2023-02-15 (Wed, 15 Feb 2023)

  Changed paths:
    M lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp

  Log Message:
  -----------
  [lldb] Remove pydoc import during script interpreter init

The Python script interpreter imports `pydoc` during initialization, but this can be
slow in some cases, and doesn't seem to be necessary any more.

This can be slow because pydoc may execute shell commands (for example `xcrun` on
macOS). The shell commands may have variable performance, depending on their caches and
search space.

The 2012 bug report for the original commit (f71a8399997bfdc1ddeeb30c6a8897554a11c382)
says the following:

> "script help" in lldb pipes the help documentation through less(1) but there's some
> problem with the key handling and often the keys you'd use to move in less (space to
> move down a page, 'q' to quit) are not received by less (they're going to lldb
> instead)

This was resolved at the time by overriding `pydoc`'s pager to be the `plainpager`
function.

I have manually tested `script help(lldb.SBDebugger)` and found no issues with the
pager, including using "space" for paging, "/" for searching, and "q" for quitting.

The presumption is that lldb and/or Python have improved I/O handling that eliminates
the original problem.

The original bug report gave an ~/.lldbinit workaround:

```
script import pydoc; pydoc.pager = pydoc.plainpager
```

Note that calling Python's `help()` will import `pydoc`, but this will only happen for
users who use `help()` from the `script` command.

Differential Revision: https://reviews.llvm.org/D144138