[Lldb-commits] [PATCH] D144138: [lldb] Remove pydoc import during script interpreter init

[Dave Lee via Phabricator via lldb-commits]

kastiglione created this revision.
kastiglione added reviewers: jasonmolenda, mib, jingham, aprantl.
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kastiglione requested review of this revision.
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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.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D144138

Files:
  lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp


Index: lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp
===================================================================
--- lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp
+++ lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp
@@ -442,7 +442,7 @@
   // do their task
   run_string.Clear();
   run_string.Printf(
-      "run_one_line (%s, 'import lldb.formatters, lldb.formatters.cpp, pydoc')",
+      "run_one_line (%s, 'import lldb.formatters, lldb.formatters.cpp')",
       m_dictionary_name.c_str());
   PyRun_SimpleString(run_string.GetData());
   run_string.Clear();
@@ -455,7 +455,7 @@
   run_string.Clear();
 
   run_string.Printf("run_one_line (%s, 'lldb.debugger_unique_id = %" PRIu64
-                    "; pydoc.pager = pydoc.plainpager')",
+                    "')",
                     m_dictionary_name.c_str(), m_debugger.GetID());
   PyRun_SimpleString(run_string.GetData());
 }


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