rust-utils: introduce a debug util to print the python stack trace

Differential Revision: https://phab.mercurial-scm.org/D7057

rust/hg-cpython/src/utils.rs

@@ -0,0 +1,13
+use cpython::{PyDict, PyObject, PyResult, PyTuple, Python};
+
+#[allow(unused)]
+pub fn print_python_trace(py: Python) -> PyResult<PyObject> {
+    eprintln!("===============================");
+    eprintln!("Printing Python stack from Rust");
+    eprintln!("===============================");
+    let traceback = py.import("traceback")?;
+    let sys = py.import("sys")?;
+    let kwargs = PyDict::new(py);
+    kwargs.set_item(py, "file", sys.get(py, "stderr")?)?;
+    traceback.call(py, "print_stack", PyTuple::new(py, &[]), Some(&kwargs))
+}

rust/hg-cpython/src/lib.rs

@@ -1,73 +1,74
 // lib.rs
 //
 // Copyright 2018 Georges Racinet <[e-mail]>
 //
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
 //! Python bindings of `hg-core` objects using the `cpython` crate.
 //! Once compiled, the resulting single shared library object can be placed in
 //! the `mercurial` package directly as `rustext.so` or `rustext.dll`.
 //! It holds several modules, so that from the point of view of Python,
 //! it behaves as the `cext` package.
 //!
 //! Example:
 //!
 //! ```text
 //! >>> from mercurial.rustext import ancestor
 //! >>> ancestor.__doc__
 //! 'Generic DAG ancestor algorithms - Rust implementation'
 //! ```
 
 /// This crate uses nested private macros, `extern crate` is still needed in
 /// 2018 edition.
 #[macro_use]
 extern crate cpython;
 
 pub mod ancestors;
 mod cindex;
 mod conversion;
 #[macro_use]
 pub mod ref_sharing;
 pub mod dagops;
 pub mod dirstate;
 pub mod discovery;
 pub mod exceptions;
 pub mod filepatterns;
 pub mod parsers;
+pub mod utils;
 
 py_module_initializer!(rustext, initrustext, PyInit_rustext, |py, m| {
     m.add(
         py,
         "__doc__",
         "Mercurial core concepts - Rust implementation",
     )?;
 
     let dotted_name: String = m.get(py, "__name__")?.extract(py)?;
     m.add(py, "ancestor", ancestors::init_module(py, &dotted_name)?)?;
     m.add(py, "dagop", dagops::init_module(py, &dotted_name)?)?;
     m.add(py, "discovery", discovery::init_module(py, &dotted_name)?)?;
     m.add(py, "dirstate", dirstate::init_module(py, &dotted_name)?)?;
     m.add(
         py,
         "filepatterns",
         filepatterns::init_module(py, &dotted_name)?,
     )?;
     m.add(
         py,
         "parsers",
         parsers::init_parsers_module(py, &dotted_name)?,
     )?;
     m.add(py, "GraphError", py.get_type::<exceptions::GraphError>())?;
     m.add(
         py,
         "PatternFileError",
         py.get_type::<exceptions::PatternFileError>(),
     )?;
     m.add(
         py,
         "PatternError",
         py.get_type::<exceptions::PatternError>(),
     )?;
     Ok(())
 });