Line data Source code
1 : #include "Python.h"
2 : #include "pycore_frame.h"
3 :
4 : #include "pycore_pyerrors.h"
5 : #include "pycore_code.h" // _PyCode_GetVarnames()
6 :
7 : #define MAX_CANDIDATE_ITEMS 750
8 : #define MAX_STRING_SIZE 40
9 :
10 : #define MOVE_COST 2
11 : #define CASE_COST 1
12 :
13 : #define LEAST_FIVE_BITS(n) ((n) & 31)
14 :
15 : static inline int
16 30181 : substitution_cost(char a, char b)
17 : {
18 30181 : if (LEAST_FIVE_BITS(a) != LEAST_FIVE_BITS(b)) {
19 : // Not the same, not a case flip.
20 28426 : return MOVE_COST;
21 : }
22 1755 : if (a == b) {
23 1131 : return 0;
24 : }
25 624 : if ('A' <= a && a <= 'Z') {
26 367 : a += ('a' - 'A');
27 : }
28 624 : if ('A' <= b && b <= 'Z') {
29 244 : b += ('a' - 'A');
30 : }
31 624 : if (a == b) {
32 610 : return CASE_COST;
33 : }
34 14 : return MOVE_COST;
35 : }
36 :
37 : /* Calculate the Levenshtein distance between string1 and string2 */
38 : static Py_ssize_t
39 4173 : levenshtein_distance(const char *a, size_t a_size,
40 : const char *b, size_t b_size,
41 : size_t max_cost)
42 : {
43 : static size_t buffer[MAX_STRING_SIZE];
44 :
45 : // Both strings are the same (by identity)
46 4173 : if (a == b) {
47 2 : return 0;
48 : }
49 :
50 : // Trim away common affixes.
51 4797 : while (a_size && b_size && a[0] == b[0]) {
52 626 : a++; a_size--;
53 626 : b++; b_size--;
54 : }
55 4388 : while (a_size && b_size && a[a_size-1] == b[b_size-1]) {
56 217 : a_size--;
57 217 : b_size--;
58 : }
59 4171 : if (a_size == 0 || b_size == 0) {
60 56 : return (a_size + b_size) * MOVE_COST;
61 : }
62 4115 : if (a_size > MAX_STRING_SIZE || b_size > MAX_STRING_SIZE) {
63 209 : return max_cost + 1;
64 : }
65 :
66 : // Prefer shorter buffer
67 3906 : if (b_size < a_size) {
68 808 : const char *t = a; a = b; b = t;
69 808 : size_t t_size = a_size; a_size = b_size; b_size = t_size;
70 : }
71 :
72 : // quick fail when a match is impossible.
73 3906 : if ((b_size - a_size) * MOVE_COST > max_cost) {
74 3126 : return max_cost + 1;
75 : }
76 :
77 : // Instead of producing the whole traditional len(a)-by-len(b)
78 : // matrix, we can update just one row in place.
79 : // Initialize the buffer row
80 780 : size_t tmp = MOVE_COST;
81 6107 : for (size_t i = 0; i < a_size; i++) {
82 : // cost from b[:0] to a[:i+1]
83 5327 : buffer[i] = tmp;
84 5327 : tmp += MOVE_COST;
85 : }
86 :
87 780 : size_t result = 0;
88 3039 : for (size_t b_index = 0; b_index < b_size; b_index++) {
89 2991 : char code = b[b_index];
90 : // cost(b[:b_index], a[:0]) == b_index * MOVE_COST
91 2991 : size_t distance = result = b_index * MOVE_COST;
92 2991 : size_t minimum = SIZE_MAX;
93 33172 : for (size_t index = 0; index < a_size; index++) {
94 :
95 : // cost(b[:b_index+1], a[:index+1]) = min(
96 : // // 1) substitute
97 : // cost(b[:b_index], a[:index])
98 : // + substitution_cost(b[b_index], a[index]),
99 : // // 2) delete from b
100 : // cost(b[:b_index], a[:index+1]) + MOVE_COST,
101 : // // 3) delete from a
102 : // cost(b[:b_index+1], a[index]) + MOVE_COST
103 : // )
104 :
105 : // 1) Previous distance in this row is cost(b[:b_index], a[:index])
106 30181 : size_t substitute = distance + substitution_cost(code, a[index]);
107 : // 2) cost(b[:b_index], a[:index+1]) from previous row
108 30181 : distance = buffer[index];
109 : // 3) existing result is cost(b[:b_index+1], a[index])
110 :
111 30181 : size_t insert_delete = Py_MIN(result, distance) + MOVE_COST;
112 30181 : result = Py_MIN(insert_delete, substitute);
113 :
114 : // cost(b[:b_index+1], a[:index+1])
115 30181 : buffer[index] = result;
116 30181 : if (result < minimum) {
117 4415 : minimum = result;
118 : }
119 : }
120 2991 : if (minimum > max_cost) {
121 : // Everything in this row is too big, so bail early.
122 732 : return max_cost + 1;
123 : }
124 : }
125 48 : return result;
126 : }
127 :
128 : static inline PyObject *
129 79 : calculate_suggestions(PyObject *dir,
130 : PyObject *name)
131 : {
132 79 : assert(!PyErr_Occurred());
133 79 : assert(PyList_CheckExact(dir));
134 :
135 79 : Py_ssize_t dir_size = PyList_GET_SIZE(dir);
136 79 : if (dir_size >= MAX_CANDIDATE_ITEMS) {
137 2 : return NULL;
138 : }
139 :
140 77 : Py_ssize_t suggestion_distance = PY_SSIZE_T_MAX;
141 77 : PyObject *suggestion = NULL;
142 : Py_ssize_t name_size;
143 77 : const char *name_str = PyUnicode_AsUTF8AndSize(name, &name_size);
144 77 : if (name_str == NULL) {
145 0 : return NULL;
146 : }
147 :
148 4161 : for (int i = 0; i < dir_size; ++i) {
149 4084 : PyObject *item = PyList_GET_ITEM(dir, i);
150 : Py_ssize_t item_size;
151 4084 : const char *item_str = PyUnicode_AsUTF8AndSize(item, &item_size);
152 4084 : if (item_str == NULL) {
153 0 : return NULL;
154 : }
155 4084 : if (PyUnicode_CompareWithASCIIString(name, item_str) == 0) {
156 4055 : continue;
157 : }
158 : // No more than 1/3 of the involved characters should need changed.
159 4083 : Py_ssize_t max_distance = (name_size + item_size + 3) * MOVE_COST / 6;
160 : // Don't take matches we've already beaten.
161 4083 : max_distance = Py_MIN(max_distance, suggestion_distance - 1);
162 : Py_ssize_t current_distance =
163 4083 : levenshtein_distance(name_str, name_size,
164 : item_str, item_size, max_distance);
165 4083 : if (current_distance > max_distance) {
166 4054 : continue;
167 : }
168 29 : if (!suggestion || current_distance < suggestion_distance) {
169 29 : suggestion = item;
170 29 : suggestion_distance = current_distance;
171 : }
172 : }
173 77 : Py_XINCREF(suggestion);
174 77 : return suggestion;
175 : }
176 :
177 : static PyObject *
178 26 : offer_suggestions_for_attribute_error(PyAttributeErrorObject *exc)
179 : {
180 26 : PyObject *name = exc->name; // borrowed reference
181 26 : PyObject *obj = exc->obj; // borrowed reference
182 :
183 : // Abort if we don't have an attribute name or we have an invalid one
184 26 : if (name == NULL || obj == NULL || !PyUnicode_CheckExact(name)) {
185 2 : return NULL;
186 : }
187 :
188 24 : PyObject *dir = PyObject_Dir(obj);
189 24 : if (dir == NULL) {
190 1 : return NULL;
191 : }
192 :
193 23 : PyObject *suggestions = calculate_suggestions(dir, name);
194 23 : Py_DECREF(dir);
195 23 : return suggestions;
196 : }
197 :
198 :
199 : static PyObject *
200 28 : offer_suggestions_for_name_error(PyNameErrorObject *exc)
201 : {
202 28 : PyObject *name = exc->name; // borrowed reference
203 28 : PyTracebackObject *traceback = (PyTracebackObject *) exc->traceback; // borrowed reference
204 : // Abort if we don't have a variable name or we have an invalid one
205 : // or if we don't have a traceback to work with
206 28 : if (name == NULL || !PyUnicode_CheckExact(name) ||
207 25 : traceback == NULL || !Py_IS_TYPE(traceback, &PyTraceBack_Type)
208 : ) {
209 5 : return NULL;
210 : }
211 :
212 : // Move to the traceback of the exception
213 17 : while (1) {
214 40 : PyTracebackObject *next = traceback->tb_next;
215 40 : if (next == NULL || !Py_IS_TYPE(next, &PyTraceBack_Type)) {
216 : break;
217 : }
218 : else {
219 17 : traceback = next;
220 : }
221 : }
222 :
223 23 : PyFrameObject *frame = traceback->tb_frame;
224 23 : assert(frame != NULL);
225 23 : PyCodeObject *code = PyFrame_GetCode(frame);
226 23 : assert(code != NULL && code->co_localsplusnames != NULL);
227 23 : PyObject *varnames = _PyCode_GetVarnames(code);
228 23 : if (varnames == NULL) {
229 0 : return NULL;
230 : }
231 23 : PyObject *dir = PySequence_List(varnames);
232 23 : Py_DECREF(varnames);
233 23 : Py_DECREF(code);
234 23 : if (dir == NULL) {
235 0 : return NULL;
236 : }
237 :
238 23 : PyObject *suggestions = calculate_suggestions(dir, name);
239 23 : Py_DECREF(dir);
240 23 : if (suggestions != NULL) {
241 6 : return suggestions;
242 : }
243 :
244 17 : dir = PySequence_List(frame->f_frame->f_globals);
245 17 : if (dir == NULL) {
246 0 : return NULL;
247 : }
248 17 : suggestions = calculate_suggestions(dir, name);
249 17 : Py_DECREF(dir);
250 17 : if (suggestions != NULL) {
251 1 : return suggestions;
252 : }
253 :
254 16 : dir = PySequence_List(frame->f_frame->f_builtins);
255 16 : if (dir == NULL) {
256 0 : return NULL;
257 : }
258 16 : suggestions = calculate_suggestions(dir, name);
259 16 : Py_DECREF(dir);
260 :
261 16 : return suggestions;
262 : }
263 :
264 : // Offer suggestions for a given exception. Returns a python string object containing the
265 : // suggestions. This function returns NULL if no suggestion was found or if an exception happened,
266 : // users must call PyErr_Occurred() to disambiguate.
267 : PyObject *
268 444 : _Py_Offer_Suggestions(PyObject *exception)
269 : {
270 444 : PyObject *result = NULL;
271 444 : assert(!PyErr_Occurred());
272 444 : if (Py_IS_TYPE(exception, (PyTypeObject*)PyExc_AttributeError)) {
273 26 : result = offer_suggestions_for_attribute_error((PyAttributeErrorObject *) exception);
274 418 : } else if (Py_IS_TYPE(exception, (PyTypeObject*)PyExc_NameError)) {
275 28 : result = offer_suggestions_for_name_error((PyNameErrorObject *) exception);
276 : }
277 444 : return result;
278 : }
279 :
280 : Py_ssize_t
281 90 : _Py_UTF8_Edit_Cost(PyObject *a, PyObject *b, Py_ssize_t max_cost)
282 : {
283 90 : assert(PyUnicode_Check(a) && PyUnicode_Check(b));
284 : Py_ssize_t size_a, size_b;
285 90 : const char *utf8_a = PyUnicode_AsUTF8AndSize(a, &size_a);
286 90 : if (utf8_a == NULL) {
287 0 : return -1;
288 : }
289 90 : const char *utf8_b = PyUnicode_AsUTF8AndSize(b, &size_b);
290 90 : if (utf8_b == NULL) {
291 0 : return -1;
292 : }
293 90 : if (max_cost == -1) {
294 19 : max_cost = MOVE_COST * Py_MAX(size_a, size_b);
295 : }
296 90 : return levenshtein_distance(utf8_a, size_a, utf8_b, size_b, max_cost);
297 : }
298 :
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