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The Python binding (kpy/): klammertext.Machine from a script

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Assembled from klammertext-dev ed13dfaa5b7a.  kpy/klammertext.cpp is a
CPython extension module giving a Python script an instance of the
Machine class -- ktext in-process, set up through the same functions the
command uses.  Errors map one-to-one to Python exceptions under the C++
names; an @eval's Python exception is chained as __cause__.  Built by
make -C mac, found through PYTHONPATH (env/runtime.env sets it), tested
by tst/kpy_test.sh.  Three engine changes came with it: Error::message(),
set_command_state(), and the @eval error report carrying its traceback.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Uv7KWxafinDPraswEf4GsC
This commit is contained in:
ackandClaude Fable 5.1 committed 2026-09-08 16:54:21 +02:00
1 parent e4f1307aa9
commit 760fda5470
17 files changed
+1241 -78
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mac/eval_python.cpp
+85 -49
View File
@@ -4,6 +4,7 @@
#include "log.h"
std::regex Eval_python::statement_delimiter("\\s*;\\s*");
PyObject* Eval_python::s_last_exception = nullptr;
Eval_python::Eval_python(Machine& machine, const Locator& loc)
: m_machine(machine)
@@ -119,52 +120,10 @@ void Eval_python::import_module(const std::string& module_name, bool verify)
}
PyObject* module = PyImport_ImportModule(module_name.c_str());
if (module == nullptr) {
// Extract the Python traceback before clearing the error.
// This reveals the actual source of the failure (e.g., a syntax
// error in a transitively imported module), not just the top-level
// module name that failed to load.
std::string detail;
PyObject* ptype;
PyObject* pvalue;
PyObject* ptraceback;
PyErr_Fetch(&ptype, &pvalue, &ptraceback);
if (pvalue) {
PyErr_NormalizeException(&ptype, &pvalue, &ptraceback);
PyObject* str = PyObject_Str(pvalue);
if (str) {
detail = PyUnicode_AsUTF8(str);
Py_DECREF(str);
}
// Format the traceback if available
if (ptraceback) {
PyObject* tb_module = PyImport_ImportModule("traceback");
if (tb_module) {
PyObject* format_tb = PyObject_GetAttrString(tb_module, "format_exception");
if (format_tb) {
PyObject* args = PyTuple_Pack(3, ptype, pvalue, ptraceback);
PyObject* tb_list = PyObject_CallObject(format_tb, args);
if (tb_list) {
PyObject* separator = PyUnicode_FromString("");
PyObject* joined = PyUnicode_Join(separator, tb_list);
if (joined) {
detail = PyUnicode_AsUTF8(joined);
Py_DECREF(joined);
}
Py_DECREF(separator);
Py_DECREF(tb_list);
}
Py_XDECREF(args);
Py_DECREF(format_tb);
}
Py_DECREF(tb_module);
}
}
}
Py_XDECREF(ptype);
Py_XDECREF(pvalue);
Py_XDECREF(ptraceback);
PyErr_Clear();
// The traceback, not just the top-level module name that failed to
// load: it reveals the actual source of the failure (e.g. a syntax
// error in a transitively imported module).
std::string detail = fetch_python_exception();
std::string message = "Cannot import module \"" + module_name + "\"";
if (!detail.empty()) {
message += ":\n\n" + detail;
@@ -176,6 +135,68 @@ void Eval_python::import_module(const std::string& module_name, bool verify)
PyDict_SetItemString(m_globals, module_name.c_str(), module);
}
PyObject* Eval_python::take_last_exception()
{
PyObject* e = s_last_exception;
s_last_exception = nullptr;
return e;
}
std::string Eval_python::fetch_python_exception()
{
std::string detail {};
PyObject* ptype = nullptr;
PyObject* pvalue = nullptr;
PyObject* ptraceback = nullptr;
PyErr_Fetch(&ptype, &pvalue, &ptraceback);
if (!pvalue) {
Py_XDECREF(ptype);
Py_XDECREF(ptraceback);
PyErr_Clear();
return detail;
}
PyErr_NormalizeException(&ptype, &pvalue, &ptraceback);
if (ptraceback) {
// Attach the traceback to the instance, so whoever receives the
// object (the binding, as __cause__) can still print it.
PyException_SetTraceback(pvalue, ptraceback);
}
PyObject* str = PyObject_Str(pvalue);
if (str) {
detail = PyUnicode_AsUTF8(str);
Py_DECREF(str);
}
PyObject* tb_module = PyImport_ImportModule("traceback");
if (tb_module) {
PyObject* format = PyObject_GetAttrString(tb_module, "format_exception");
if (format) {
PyObject* args = PyTuple_Pack(
3, ptype, pvalue, ptraceback ? ptraceback : Py_None);
PyObject* tb_list = PyObject_CallObject(format, args);
if (tb_list) {
PyObject* separator = PyUnicode_FromString("");
PyObject* joined = PyUnicode_Join(separator, tb_list);
if (joined) {
detail = PyUnicode_AsUTF8(joined);
Py_DECREF(joined);
}
Py_DECREF(separator);
Py_DECREF(tb_list);
}
Py_XDECREF(args);
Py_DECREF(format);
}
Py_DECREF(tb_module);
}
// Keep the instance (it owns its traceback now); drop the rest.
Py_XDECREF(s_last_exception);
s_last_exception = pvalue;
Py_XDECREF(ptype);
Py_XDECREF(ptraceback);
PyErr_Clear();
return detail;
}
std::string Eval_python::get_result(PyObject* result_object)
{
std::string result {};
@@ -184,9 +205,24 @@ std::string Eval_python::get_result(PyObject* result_object)
result = std::string(value);
Py_DECREF(result_object);
} else {
std::cout << red;
PyErr_Print();
throw Parsing_error("Python code error in @eval", m_loc);
// Until 2026-09-08 this was "std::cout << red; PyErr_Print();" --
// the colour escape on stdout, the traceback on stderr, and then an
// Error carrying neither. The traceback now travels IN the error,
// indented so justify() leaves its lines verbatim (a traceback line
// is not prose), and the exception object is kept for the binding.
std::string detail = fetch_python_exception();
std::string message = "Python code error in @eval";
if (!detail.empty()) {
message += ":\n\n";
std::string::size_type from = 0;
while (from < detail.size()) {
auto nl = detail.find('\n', from);
if (nl == std::string::npos) nl = detail.size();
message += " " + detail.substr(from, nl - from) + "\n";
from = nl + 1;
}
}
throw Parsing_error(message, m_loc);
}
return result;
}