Python/suggestions.c - platform/external/python/cpython3 - Git at Google

 #include "Python.h"
 #include "pycore_frame.h"

 #include "pycore_pyerrors.h"
 #include "pycore_code.h"        // _PyCode_GetVarnames()

 #define MAX_CANDIDATE_ITEMS 750
 #define MAX_STRING_SIZE 40

 #define MOVE_COST 2
 #define CASE_COST 1

 #define LEAST_FIVE_BITS(n) ((n) & 31)

 static inline int
 substitution_cost(char a, char b)
 {
     if (LEAST_FIVE_BITS(a) != LEAST_FIVE_BITS(b)) {
         // Not the same, not a case flip.
         return MOVE_COST;
     }
     if (a == b) {
         return 0;
     }
     if ('A' <= a && a <= 'Z') {
         a += ('a' - 'A');
     }
     if ('A' <= b && b <= 'Z') {
         b += ('a' - 'A');
     }
     if (a == b) {
         return CASE_COST;
     }
     return MOVE_COST;
 }

 /* Calculate the Levenshtein distance between string1 and string2 */
 static Py_ssize_t
 levenshtein_distance(const char *a, size_t a_size,
                      const char *b, size_t b_size,
                      size_t max_cost)
 {
     static size_t buffer[MAX_STRING_SIZE];

     // Both strings are the same (by identity)
     if (a == b) {
         return 0;
     }

     // Trim away common affixes.
     while (a_size && b_size && a[0] == b[0]) {
         a++; a_size--;
         b++; b_size--;
     }
     while (a_size && b_size && a[a_size-1] == b[b_size-1]) {
         a_size--;
         b_size--;
     }
     if (a_size == 0 || b_size == 0) {
         return (a_size + b_size) * MOVE_COST;
     }
     if (a_size > MAX_STRING_SIZE || b_size > MAX_STRING_SIZE) {
         return max_cost + 1;
     }

     // Prefer shorter buffer
     if (b_size < a_size) {
         const char *t = a; a = b; b = t;
         size_t t_size = a_size; a_size = b_size; b_size = t_size;
     }

     // quick fail when a match is impossible.
     if ((b_size - a_size) * MOVE_COST > max_cost) {
         return max_cost + 1;
     }

     // Instead of producing the whole traditional len(a)-by-len(b)
     // matrix, we can update just one row in place.
     // Initialize the buffer row
     size_t tmp = MOVE_COST;
     for (size_t i = 0; i < a_size; i++) {
         // cost from b[:0] to a[:i+1]
         buffer[i] = tmp;
         tmp += MOVE_COST;
     }

     size_t result = 0;
     for (size_t b_index = 0; b_index < b_size; b_index++) {
         char code = b[b_index];
         // cost(b[:b_index], a[:0]) == b_index * MOVE_COST
         size_t distance = result = b_index * MOVE_COST;
         size_t minimum = SIZE_MAX;
         for (size_t index = 0; index < a_size; index++) {

             // cost(b[:b_index+1], a[:index+1]) = min(
             //     // 1) substitute
             //     cost(b[:b_index], a[:index])
             //         + substitution_cost(b[b_index], a[index]),
             //     // 2) delete from b
             //     cost(b[:b_index], a[:index+1]) + MOVE_COST,
             //     // 3) delete from a
             //     cost(b[:b_index+1], a[index]) + MOVE_COST
             // )

             // 1) Previous distance in this row is cost(b[:b_index], a[:index])
             size_t substitute = distance + substitution_cost(code, a[index]);
             // 2) cost(b[:b_index], a[:index+1]) from previous row
             distance = buffer[index];
             // 3) existing result is cost(b[:b_index+1], a[index])

             size_t insert_delete = Py_MIN(result, distance) + MOVE_COST;
             result = Py_MIN(insert_delete, substitute);

             // cost(b[:b_index+1], a[:index+1])
             buffer[index] = result;
             if (result < minimum) {
                 minimum = result;
             }
         }
         if (minimum > max_cost) {
             // Everything in this row is too big, so bail early.
             return max_cost + 1;
         }
     }
     return result;
 }

 static inline PyObject *
 calculate_suggestions(PyObject *dir,
                       PyObject *name)
 {
     assert(!PyErr_Occurred());
     assert(PyList_CheckExact(dir));

     Py_ssize_t dir_size = PyList_GET_SIZE(dir);
     if (dir_size >= MAX_CANDIDATE_ITEMS) {
         return NULL;
     }

     Py_ssize_t suggestion_distance = PY_SSIZE_T_MAX;
     PyObject *suggestion = NULL;
     Py_ssize_t name_size;
     const char *name_str = PyUnicode_AsUTF8AndSize(name, &name_size);
     if (name_str == NULL) {
         return NULL;
     }

     for (int i = 0; i < dir_size; ++i) {
         PyObject *item = PyList_GET_ITEM(dir, i);
         Py_ssize_t item_size;
         const char *item_str = PyUnicode_AsUTF8AndSize(item, &item_size);
         if (item_str == NULL) {
             return NULL;
         }
         if (PyUnicode_CompareWithASCIIString(name, item_str) == 0) {
             continue;
         }
         // No more than 1/3 of the involved characters should need changed.
         Py_ssize_t max_distance = (name_size + item_size + 3) * MOVE_COST / 6;
         // Don't take matches we've already beaten.
         max_distance = Py_MIN(max_distance, suggestion_distance - 1);
         Py_ssize_t current_distance =
             levenshtein_distance(name_str, name_size,
                                  item_str, item_size, max_distance);
         if (current_distance > max_distance) {
             continue;
         }
         if (!suggestion || current_distance < suggestion_distance) {
             suggestion = item;
             suggestion_distance = current_distance;
         }
     }
     Py_XINCREF(suggestion);
     return suggestion;
 }

 static PyObject *
 offer_suggestions_for_attribute_error(PyAttributeErrorObject *exc)
 {
     PyObject *name = exc->name; // borrowed reference
     PyObject *obj = exc->obj; // borrowed reference

     // Abort if we don't have an attribute name or we have an invalid one
     if (name == NULL || obj == NULL || !PyUnicode_CheckExact(name)) {
         return NULL;
     }

     PyObject *dir = PyObject_Dir(obj);
     if (dir == NULL) {
         return NULL;
     }

     PyObject *suggestions = calculate_suggestions(dir, name);
     Py_DECREF(dir);
     return suggestions;
 }


 static PyObject *
 offer_suggestions_for_name_error(PyNameErrorObject *exc)
 {
     PyObject *name = exc->name; // borrowed reference
     PyTracebackObject *traceback = (PyTracebackObject *) exc->traceback; // borrowed reference
     // Abort if we don't have a variable name or we have an invalid one
     // or if we don't have a traceback to work with
     if (name == NULL || !PyUnicode_CheckExact(name) ||
         traceback == NULL || !Py_IS_TYPE(traceback, &PyTraceBack_Type)
     ) {
         return NULL;
     }

     // Move to the traceback of the exception
     while (1) {
         PyTracebackObject *next = traceback->tb_next;
         if (next == NULL || !Py_IS_TYPE(next, &PyTraceBack_Type)) {
             break;
         }
         else {
             traceback = next;
         }
     }

     PyFrameObject *frame = traceback->tb_frame;
     assert(frame != NULL);
     PyCodeObject *code = PyFrame_GetCode(frame);
     assert(code != NULL && code->co_localsplusnames != NULL);
     PyObject *varnames = _PyCode_GetVarnames(code);
     if (varnames == NULL) {
         return NULL;
     }
     PyObject *dir = PySequence_List(varnames);
     Py_DECREF(varnames);
     Py_DECREF(code);
     if (dir == NULL) {
         return NULL;
     }

     PyObject *suggestions = calculate_suggestions(dir, name);
     Py_DECREF(dir);
     if (suggestions != NULL) {
         return suggestions;
     }

     dir = PySequence_List(frame->f_frame->f_globals);
     if (dir == NULL) {
         return NULL;
     }
     suggestions = calculate_suggestions(dir, name);
     Py_DECREF(dir);
     if (suggestions != NULL) {
         return suggestions;
     }

     dir = PySequence_List(frame->f_frame->f_builtins);
     if (dir == NULL) {
         return NULL;
     }
     suggestions = calculate_suggestions(dir, name);
     Py_DECREF(dir);

     return suggestions;
 }

 // Offer suggestions for a given exception. Returns a python string object containing the
 // suggestions. This function returns NULL if no suggestion was found or if an exception happened,
 // users must call PyErr_Occurred() to disambiguate.
 PyObject *
 _Py_Offer_Suggestions(PyObject *exception)
 {
     PyObject *result = NULL;
     assert(!PyErr_Occurred());
     if (Py_IS_TYPE(exception, (PyTypeObject*)PyExc_AttributeError)) {
         result = offer_suggestions_for_attribute_error((PyAttributeErrorObject *) exception);
     } else if (Py_IS_TYPE(exception, (PyTypeObject*)PyExc_NameError)) {
         result = offer_suggestions_for_name_error((PyNameErrorObject *) exception);
     }
     return result;
 }

 Py_ssize_t
 _Py_UTF8_Edit_Cost(PyObject *a, PyObject *b, Py_ssize_t max_cost)
 {
     assert(PyUnicode_Check(a) && PyUnicode_Check(b));
     Py_ssize_t size_a, size_b;
     const char *utf8_a = PyUnicode_AsUTF8AndSize(a, &size_a);
     if (utf8_a == NULL) {
         return -1;
     }
     const char *utf8_b = PyUnicode_AsUTF8AndSize(b, &size_b);
     if (utf8_b == NULL) {
         return -1;
     }
     if (max_cost == -1) {
         max_cost = MOVE_COST * Py_MAX(size_a, size_b);
     }
     return levenshtein_distance(utf8_a, size_a, utf8_b, size_b, max_cost);
 }
	#include "Python.h"
	#include "pycore_frame.h"

	#include "pycore_pyerrors.h"
	#include "pycore_code.h" // _PyCode_GetVarnames()

	#define MAX_CANDIDATE_ITEMS 750
	#define MAX_STRING_SIZE 40

	#define MOVE_COST 2
	#define CASE_COST 1

	#define LEAST_FIVE_BITS(n) ((n) & 31)

	static inline int
	substitution_cost(char a, char b)
	{
	if (LEAST_FIVE_BITS(a) != LEAST_FIVE_BITS(b)) {
	// Not the same, not a case flip.
	return MOVE_COST;
	}
	if (a == b) {
	return 0;
	}
	if ('A' <= a && a <= 'Z') {
	a += ('a' - 'A');
	}
	if ('A' <= b && b <= 'Z') {
	b += ('a' - 'A');
	}
	if (a == b) {
	return CASE_COST;
	}
	return MOVE_COST;
	}

	/* Calculate the Levenshtein distance between string1 and string2 */
	static Py_ssize_t
	levenshtein_distance(const char *a, size_t a_size,
	const char *b, size_t b_size,
	size_t max_cost)
	{
	static size_t buffer[MAX_STRING_SIZE];

	// Both strings are the same (by identity)
	if (a == b) {
	return 0;
	}

	// Trim away common affixes.
	while (a_size && b_size && a[0] == b[0]) {
	a++; a_size--;
	b++; b_size--;
	}
	while (a_size && b_size && a[a_size-1] == b[b_size-1]) {
	a_size--;
	b_size--;
	}
	if (a_size == 0 \|\| b_size == 0) {
	return (a_size + b_size) * MOVE_COST;
	}
	if (a_size > MAX_STRING_SIZE \|\| b_size > MAX_STRING_SIZE) {
	return max_cost + 1;
	}

	// Prefer shorter buffer
	if (b_size < a_size) {
	const char *t = a; a = b; b = t;
	size_t t_size = a_size; a_size = b_size; b_size = t_size;
	}

	// quick fail when a match is impossible.
	if ((b_size - a_size) * MOVE_COST > max_cost) {
	return max_cost + 1;
	}

	// Instead of producing the whole traditional len(a)-by-len(b)
	// matrix, we can update just one row in place.
	// Initialize the buffer row
	size_t tmp = MOVE_COST;
	for (size_t i = 0; i < a_size; i++) {
	// cost from b[:0] to a[:i+1]
	buffer[i] = tmp;
	tmp += MOVE_COST;
	}

	size_t result = 0;
	for (size_t b_index = 0; b_index < b_size; b_index++) {
	char code = b[b_index];
	// cost(b[:b_index], a[:0]) == b_index * MOVE_COST
	size_t distance = result = b_index * MOVE_COST;
	size_t minimum = SIZE_MAX;
	for (size_t index = 0; index < a_size; index++) {

	// cost(b[:b_index+1], a[:index+1]) = min(
	// // 1) substitute
	// cost(b[:b_index], a[:index])
	// + substitution_cost(b[b_index], a[index]),
	// // 2) delete from b
	// cost(b[:b_index], a[:index+1]) + MOVE_COST,
	// // 3) delete from a
	// cost(b[:b_index+1], a[index]) + MOVE_COST
	// )

	// 1) Previous distance in this row is cost(b[:b_index], a[:index])
	size_t substitute = distance + substitution_cost(code, a[index]);
	// 2) cost(b[:b_index], a[:index+1]) from previous row
	distance = buffer[index];
	// 3) existing result is cost(b[:b_index+1], a[index])

	size_t insert_delete = Py_MIN(result, distance) + MOVE_COST;
	result = Py_MIN(insert_delete, substitute);

	// cost(b[:b_index+1], a[:index+1])
	buffer[index] = result;
	if (result < minimum) {
	minimum = result;
	}
	}
	if (minimum > max_cost) {
	// Everything in this row is too big, so bail early.
	return max_cost + 1;
	}
	}
	return result;
	}

	static inline PyObject *
	calculate_suggestions(PyObject *dir,
	PyObject *name)
	{
	assert(!PyErr_Occurred());
	assert(PyList_CheckExact(dir));

	Py_ssize_t dir_size = PyList_GET_SIZE(dir);
	if (dir_size >= MAX_CANDIDATE_ITEMS) {
	return NULL;
	}

	Py_ssize_t suggestion_distance = PY_SSIZE_T_MAX;
	PyObject *suggestion = NULL;
	Py_ssize_t name_size;
	const char *name_str = PyUnicode_AsUTF8AndSize(name, &name_size);
	if (name_str == NULL) {
	return NULL;
	}

	for (int i = 0; i < dir_size; ++i) {
	PyObject *item = PyList_GET_ITEM(dir, i);
	Py_ssize_t item_size;
	const char *item_str = PyUnicode_AsUTF8AndSize(item, &item_size);
	if (item_str == NULL) {
	return NULL;
	}
	if (PyUnicode_CompareWithASCIIString(name, item_str) == 0) {
	continue;
	}
	// No more than 1/3 of the involved characters should need changed.
	Py_ssize_t max_distance = (name_size + item_size + 3) * MOVE_COST / 6;
	// Don't take matches we've already beaten.
	max_distance = Py_MIN(max_distance, suggestion_distance - 1);
	Py_ssize_t current_distance =
	levenshtein_distance(name_str, name_size,
	item_str, item_size, max_distance);
	if (current_distance > max_distance) {
	continue;
	}
	if (!suggestion \|\| current_distance < suggestion_distance) {
	suggestion = item;
	suggestion_distance = current_distance;
	}
	}
	Py_XINCREF(suggestion);
	return suggestion;
	}

	static PyObject *
	offer_suggestions_for_attribute_error(PyAttributeErrorObject *exc)
	{
	PyObject *name = exc->name; // borrowed reference
	PyObject *obj = exc->obj; // borrowed reference

	// Abort if we don't have an attribute name or we have an invalid one
	if (name == NULL \|\| obj == NULL \|\| !PyUnicode_CheckExact(name)) {
	return NULL;
	}

	PyObject *dir = PyObject_Dir(obj);
	if (dir == NULL) {
	return NULL;
	}

	PyObject *suggestions = calculate_suggestions(dir, name);
	Py_DECREF(dir);
	return suggestions;
	}


	static PyObject *
	offer_suggestions_for_name_error(PyNameErrorObject *exc)
	{
	PyObject *name = exc->name; // borrowed reference
	PyTracebackObject traceback = (PyTracebackObject ) exc->traceback; // borrowed reference
	// Abort if we don't have a variable name or we have an invalid one
	// or if we don't have a traceback to work with
	if (name == NULL \|\| !PyUnicode_CheckExact(name) \|\|
	traceback == NULL \|\| !Py_IS_TYPE(traceback, &PyTraceBack_Type)
	) {
	return NULL;
	}

	// Move to the traceback of the exception
	while (1) {
	PyTracebackObject *next = traceback->tb_next;
	if (next == NULL \|\| !Py_IS_TYPE(next, &PyTraceBack_Type)) {
	break;
	}
	else {
	traceback = next;
	}
	}

	PyFrameObject *frame = traceback->tb_frame;
	assert(frame != NULL);
	PyCodeObject *code = PyFrame_GetCode(frame);
	assert(code != NULL && code->co_localsplusnames != NULL);
	PyObject *varnames = _PyCode_GetVarnames(code);
	if (varnames == NULL) {
	return NULL;
	}
	PyObject *dir = PySequence_List(varnames);
	Py_DECREF(varnames);
	Py_DECREF(code);
	if (dir == NULL) {
	return NULL;
	}

	PyObject *suggestions = calculate_suggestions(dir, name);
	Py_DECREF(dir);
	if (suggestions != NULL) {
	return suggestions;
	}

	dir = PySequence_List(frame->f_frame->f_globals);
	if (dir == NULL) {
	return NULL;
	}
	suggestions = calculate_suggestions(dir, name);
	Py_DECREF(dir);
	if (suggestions != NULL) {
	return suggestions;
	}

	dir = PySequence_List(frame->f_frame->f_builtins);
	if (dir == NULL) {
	return NULL;
	}
	suggestions = calculate_suggestions(dir, name);
	Py_DECREF(dir);

	return suggestions;
	}

	// Offer suggestions for a given exception. Returns a python string object containing the
	// suggestions. This function returns NULL if no suggestion was found or if an exception happened,
	// users must call PyErr_Occurred() to disambiguate.
	PyObject *
	_Py_Offer_Suggestions(PyObject *exception)
	{
	PyObject *result = NULL;
	assert(!PyErr_Occurred());
	if (Py_IS_TYPE(exception, (PyTypeObject*)PyExc_AttributeError)) {
	result = offer_suggestions_for_attribute_error((PyAttributeErrorObject *) exception);
	} else if (Py_IS_TYPE(exception, (PyTypeObject*)PyExc_NameError)) {
	result = offer_suggestions_for_name_error((PyNameErrorObject *) exception);
	}
	return result;
	}

	Py_ssize_t
	_Py_UTF8_Edit_Cost(PyObject a, PyObject b, Py_ssize_t max_cost)
	{
	assert(PyUnicode_Check(a) && PyUnicode_Check(b));
	Py_ssize_t size_a, size_b;
	const char *utf8_a = PyUnicode_AsUTF8AndSize(a, &size_a);
	if (utf8_a == NULL) {
	return -1;
	}
	const char *utf8_b = PyUnicode_AsUTF8AndSize(b, &size_b);
	if (utf8_b == NULL) {
	return -1;
	}
	if (max_cost == -1) {
	max_cost = MOVE_COST * Py_MAX(size_a, size_b);
	}
	return levenshtein_distance(utf8_a, size_a, utf8_b, size_b, max_cost);
	}