cpython/Parser/string_parser.c at autoconf-config-update · python-emscripten/cpython · GitHub

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#include <Python.h>

#include "tokenizer.h"

#include "pegen.h"

#include "string_parser.h"

//// STRING HANDLING FUNCTIONS ////

// These functions are ported directly from Python/ast.c with some modifications

// to account for the use of "Parser *p", the fact that don't have parser nodes

// to pass around and the usage of some specialized APIs present only in this

// file (like "_PyPegen_raise_syntax_error").

static int

warn_invalid_escape_sequence(Parser *p, unsigned char first_invalid_escape_char, Token *t)

{

PyObject *msg =

PyUnicode_FromFormat("invalid escape sequence \\%c", first_invalid_escape_char);

if (msg == NULL) {

return -1;

}

if (PyErr_WarnExplicitObject(PyExc_DeprecationWarning, msg, p->tok->filename,

t->lineno, NULL, NULL) < 0) {

if (PyErr_ExceptionMatches(PyExc_DeprecationWarning)) {

/* Replace the DeprecationWarning exception with a SyntaxError

to get a more accurate error report */

PyErr_Clear();

/* This is needed, in order for the SyntaxError to point to the token t,

since _PyPegen_raise_error uses p->tokens[p->fill - 1] for the

error location, if p->known_err_token is not set. */

p->known_err_token = t;

RAISE_SYNTAX_ERROR("invalid escape sequence \\%c", first_invalid_escape_char);

}

Py_DECREF(msg);

return -1;

}

Py_DECREF(msg);

return 0;

}

static PyObject *

decode_utf8(const char **sPtr, const char *end)

{

const char *s, *t;

t = s = *sPtr;

while (s < end && (*s & 0x80)) {

s++;

}

*sPtr = s;

return PyUnicode_DecodeUTF8(t, s - t, NULL);

}

static PyObject *

decode_unicode_with_escapes(Parser *parser, const char *s, size_t len, Token *t)

{

PyObject *v, *u;

char *buf;

char *p;

const char *end;

/* check for integer overflow */

if (len > SIZE_MAX / 6) {

return NULL;

}

/* "ä" (2 bytes) may become "\U000000E4" (10 bytes), or 1:5

"\ä" (3 bytes) may become "\u005c\U000000E4" (16 bytes), or ~1:6 */

u = PyBytes_FromStringAndSize((char *)NULL, len * 6);

if (u == NULL) {

return NULL;

}

p = buf = PyBytes_AsString(u);

end = s + len;

while (s < end) {

if (*s == '\\') {

*p++ = *s++;

if (s >= end || *s & 0x80) {

strcpy(p, "u005c");

p += 5;

if (s >= end) {

break;

}

if (*s & 0x80) {

PyObject *w;

int kind;

void *data;

Py_ssize_t len, i;

w = decode_utf8(&s, end);

if (w == NULL) {

Py_DECREF(u);

return NULL;

}

kind = PyUnicode_KIND(w);

data = PyUnicode_DATA(w);

len = PyUnicode_GET_LENGTH(w);

for (i = 0; i < len; i++) {

Py_UCS4 chr = PyUnicode_READ(kind, data, i);

sprintf(p, "\\U%08x", chr);

p += 10;

}

/* Should be impossible to overflow */

assert(p - buf <= PyBytes_GET_SIZE(u));

Py_DECREF(w);

}

else {

*p++ = *s++;

}

len = p - buf;

s = buf;

const char *first_invalid_escape;

v = _PyUnicode_DecodeUnicodeEscape(s, len, NULL, &first_invalid_escape);

if (v != NULL && first_invalid_escape != NULL) {

if (warn_invalid_escape_sequence(parser, *first_invalid_escape, t) < 0) {

/* We have not decref u before because first_invalid_escape points

inside u. */

Py_XDECREF(u);

Py_DECREF(v);

return NULL;

}

Py_XDECREF(u);

return v;

}

static PyObject *

decode_bytes_with_escapes(Parser *p, const char *s, Py_ssize_t len, Token *t)

{

const char *first_invalid_escape;

PyObject *result = _PyBytes_DecodeEscape(s, len, NULL, &first_invalid_escape);

if (result == NULL) {

return NULL;

}

if (first_invalid_escape != NULL) {

if (warn_invalid_escape_sequence(p, *first_invalid_escape, t) < 0) {

Py_DECREF(result);

return NULL;

}

return result;

}

/* s must include the bracketing quote characters, and r, b, u,

&/or f prefixes (if any), and embedded escape sequences (if any).

_PyPegen_parsestr parses it, and sets *result to decoded Python string object.

If the string is an f-string, set *fstr and *fstrlen to the unparsed

string object. Return 0 if no errors occurred. */

int

_PyPegen_parsestr(Parser *p, int *bytesmode, int *rawmode, PyObject **result,

const char **fstr, Py_ssize_t *fstrlen, Token *t)

{

const char *s = PyBytes_AsString(t->bytes);

if (s == NULL) {

return -1;

}

size_t len;

int quote = Py_CHARMASK(*s);

int fmode = 0;

*bytesmode = 0;

*rawmode = 0;

*result = NULL;

*fstr = NULL;

if (Py_ISALPHA(quote)) {

while (!*bytesmode || !*rawmode) {

if (quote == 'b' || quote == 'B') {

quote = *++s;

*bytesmode = 1;

}

else if (quote == 'u' || quote == 'U') {

quote = *++s;

}

else if (quote == 'r' || quote == 'R') {

quote = *++s;

*rawmode = 1;

}

else if (quote == 'f' || quote == 'F') {

quote = *++s;

fmode = 1;

}

else {

break;

}

/* fstrings are only allowed in Python 3.6 and greater */

if (fmode && p->feature_version < 6) {

p->error_indicator = 1;

RAISE_SYNTAX_ERROR("Format strings are only supported in Python 3.6 and greater");

return -1;

}

if (fmode && *bytesmode) {

PyErr_BadInternalCall();

return -1;

}

if (quote != '\'' && quote != '\"') {

PyErr_BadInternalCall();

return -1;

}

/* Skip the leading quote char. */

s++;

len = strlen(s);

if (len > INT_MAX) {

PyErr_SetString(PyExc_OverflowError, "string to parse is too long");

return -1;

}

if (s[--len] != quote) {

/* Last quote char must match the first. */

PyErr_BadInternalCall();

return -1;

}

if (len >= 4 && s[0] == quote && s[1] == quote) {

/* A triple quoted string. We've already skipped one quote at

the start and one at the end of the string. Now skip the

two at the start. */

s += 2;

len -= 2;

/* And check that the last two match. */

if (s[--len] != quote || s[--len] != quote) {

PyErr_BadInternalCall();

return -1;

}

if (fmode) {

/* Just return the bytes. The caller will parse the resulting

string. */

*fstr = s;

*fstrlen = len;

return 0;

}

/* Not an f-string. */

/* Avoid invoking escape decoding routines if possible. */

*rawmode = *rawmode || strchr(s, '\\') == NULL;

if (*bytesmode) {

/* Disallow non-ASCII characters. */

const char *ch;

for (ch = s; *ch; ch++) {

if (Py_CHARMASK(*ch) >= 0x80) {

RAISE_SYNTAX_ERROR(

"bytes can only contain ASCII "

"literal characters.");

return -1;

}

if (*rawmode) {

*result = PyBytes_FromStringAndSize(s, len);

}

else {

*result = decode_bytes_with_escapes(p, s, len, t);

}

else {

if (*rawmode) {

*result = PyUnicode_DecodeUTF8Stateful(s, len, NULL, NULL);

}

else {

*result = decode_unicode_with_escapes(p, s, len, t);

}

return *result == NULL ? -1 : 0;

}

// FSTRING STUFF

static void fstring_shift_expr_locations(expr_ty n, int lineno, int col_offset);

static void fstring_shift_argument(expr_ty parent, arg_ty args, int lineno, int col_offset);

static inline void shift_expr(expr_ty parent, expr_ty n, int line, int col) {

if (n == NULL) {

return;

}

if (parent->lineno < n->lineno) {

col = 0;

}

fstring_shift_expr_locations(n, line, col);

}

static inline void shift_arg(expr_ty parent, arg_ty n, int line, int col) {

if (parent->lineno < n->lineno) {

col = 0;

}

fstring_shift_argument(parent, n, line, col);

}

static void fstring_shift_seq_locations(expr_ty parent, asdl_seq *seq, int lineno, int col_offset) {

for (Py_ssize_t i = 0, l = asdl_seq_LEN(seq); i < l; i++) {

expr_ty expr = asdl_seq_GET(seq, i);

if (expr == NULL){

continue;

}

shift_expr(parent, expr, lineno, col_offset);

}

static void fstring_shift_slice_locations(expr_ty parent, expr_ty slice, int lineno, int col_offset) {

switch (slice->kind) {

case Slice_kind:

if (slice->v.Slice.lower) {

shift_expr(parent, slice->v.Slice.lower, lineno, col_offset);

}

if (slice->v.Slice.upper) {

shift_expr(parent, slice->v.Slice.upper, lineno, col_offset);

}

if (slice->v.Slice.step) {

shift_expr(parent, slice->v.Slice.step, lineno, col_offset);

}

break;

case Tuple_kind:

fstring_shift_seq_locations(parent, slice->v.Tuple.elts, lineno, col_offset);

break;

default:

break;

}

static void fstring_shift_comprehension(expr_ty parent, comprehension_ty comp, int lineno, int col_offset) {

shift_expr(parent, comp->target, lineno, col_offset);

shift_expr(parent, comp->iter, lineno, col_offset);

fstring_shift_seq_locations(parent, comp->ifs, lineno, col_offset);

}

static void fstring_shift_argument(expr_ty parent, arg_ty arg, int lineno, int col_offset) {

if (arg->annotation != NULL){

shift_expr(parent, arg->annotation, lineno, col_offset);

}

arg->col_offset = arg->col_offset + col_offset;

arg->end_col_offset = arg->end_col_offset + col_offset;

arg->lineno = arg->lineno + lineno;

arg->end_lineno = arg->end_lineno + lineno;

}

static void fstring_shift_arguments(expr_ty parent, arguments_ty args, int lineno, int col_offset) {

for (Py_ssize_t i = 0, l = asdl_seq_LEN(args->posonlyargs); i < l; i++) {

arg_ty arg = asdl_seq_GET(args->posonlyargs, i);

shift_arg(parent, arg, lineno, col_offset);

}

for (Py_ssize_t i = 0, l = asdl_seq_LEN(args->args); i < l; i++) {

arg_ty arg = asdl_seq_GET(args->args, i);

shift_arg(parent, arg, lineno, col_offset);

}

if (args->vararg != NULL) {

shift_arg(parent, args->vararg, lineno, col_offset);

}

for (Py_ssize_t i = 0, l = asdl_seq_LEN(args->kwonlyargs); i < l; i++) {

arg_ty arg = asdl_seq_GET(args->kwonlyargs, i);

shift_arg(parent, arg, lineno, col_offset);

}

fstring_shift_seq_locations(parent, args->kw_defaults, lineno, col_offset);

if (args->kwarg != NULL) {

shift_arg(parent, args->kwarg, lineno, col_offset);

}

fstring_shift_seq_locations(parent, args->defaults, lineno, col_offset);

}

static void fstring_shift_children_locations(expr_ty n, int lineno, int col_offset) {

switch (n->kind) {

case BoolOp_kind:

fstring_shift_seq_locations(n, n->v.BoolOp.values, lineno, col_offset);

break;

case NamedExpr_kind:

shift_expr(n, n->v.NamedExpr.target, lineno, col_offset);

shift_expr(n, n->v.NamedExpr.value, lineno, col_offset);

break;

case BinOp_kind:

shift_expr(n, n->v.BinOp.left, lineno, col_offset);

shift_expr(n, n->v.BinOp.right, lineno, col_offset);

break;

case UnaryOp_kind:

shift_expr(n, n->v.UnaryOp.operand, lineno, col_offset);

break;

case Lambda_kind:

fstring_shift_arguments(n, n->v.Lambda.args, lineno, col_offset);

shift_expr(n, n->v.Lambda.body, lineno, col_offset);

break;

case IfExp_kind:

shift_expr(n, n->v.IfExp.test, lineno, col_offset);

shift_expr(n, n->v.IfExp.body, lineno, col_offset);

shift_expr(n, n->v.IfExp.orelse, lineno, col_offset);

break;

case Dict_kind:

fstring_shift_seq_locations(n, n->v.Dict.keys, lineno, col_offset);

fstring_shift_seq_locations(n, n->v.Dict.values, lineno, col_offset);

break;

case Set_kind:

fstring_shift_seq_locations(n, n->v.Set.elts, lineno, col_offset);

break;

case ListComp_kind:

shift_expr(n, n->v.ListComp.elt, lineno, col_offset);

for (Py_ssize_t i = 0, l = asdl_seq_LEN(n->v.ListComp.generators); i < l; i++) {

comprehension_ty comp = asdl_seq_GET(n->v.ListComp.generators, i);

fstring_shift_comprehension(n, comp, lineno, col_offset);

}

break;

case SetComp_kind:

shift_expr(n, n->v.SetComp.elt, lineno, col_offset);

for (Py_ssize_t i = 0, l = asdl_seq_LEN(n->v.SetComp.generators); i < l; i++) {

comprehension_ty comp = asdl_seq_GET(n->v.SetComp.generators, i);

fstring_shift_comprehension(n, comp, lineno, col_offset);

}

break;

case DictComp_kind:

shift_expr(n, n->v.DictComp.key, lineno, col_offset);

shift_expr(n, n->v.DictComp.value, lineno, col_offset);

for (Py_ssize_t i = 0, l = asdl_seq_LEN(n->v.DictComp.generators); i < l; i++) {

comprehension_ty comp = asdl_seq_GET(n->v.DictComp.generators, i);

fstring_shift_comprehension(n, comp, lineno, col_offset);

}

break;

case GeneratorExp_kind:

shift_expr(n, n->v.GeneratorExp.elt, lineno, col_offset);

for (Py_ssize_t i = 0, l = asdl_seq_LEN(n->v.GeneratorExp.generators); i < l; i++) {

comprehension_ty comp = asdl_seq_GET(n->v.GeneratorExp.generators, i);

fstring_shift_comprehension(n, comp, lineno, col_offset);

}

break;

case Await_kind:

shift_expr(n, n->v.Await.value, lineno, col_offset);

break;

case Yield_kind:

shift_expr(n, n->v.Yield.value, lineno, col_offset);

break;

case YieldFrom_kind:

shift_expr(n, n->v.YieldFrom.value, lineno, col_offset);

break;

case Compare_kind:

shift_expr(n, n->v.Compare.left, lineno, col_offset);

fstring_shift_seq_locations(n, n->v.Compare.comparators, lineno, col_offset);

break;

case Call_kind:

shift_expr(n, n->v.Call.func, lineno, col_offset);

fstring_shift_seq_locations(n, n->v.Call.args, lineno, col_offset);

for (Py_ssize_t i = 0, l = asdl_seq_LEN(n->v.Call.keywords); i < l; i++) {

keyword_ty keyword = asdl_seq_GET(n->v.Call.keywords, i);

shift_expr(n, keyword->value, lineno, col_offset);

}

break;

case Attribute_kind:

shift_expr(n, n->v.Attribute.value, lineno, col_offset);

break;

case Subscript_kind:

shift_expr(n, n->v.Subscript.value, lineno, col_offset);

fstring_shift_slice_locations(n, n->v.Subscript.slice, lineno, col_offset);

shift_expr(n, n->v.Subscript.slice, lineno, col_offset);

break;

case Starred_kind:

shift_expr(n, n->v.Starred.value, lineno, col_offset);

break;

case List_kind:

fstring_shift_seq_locations(n, n->v.List.elts, lineno, col_offset);

break;

case Tuple_kind:

fstring_shift_seq_locations(n, n->v.Tuple.elts, lineno, col_offset);

break;

case JoinedStr_kind:

fstring_shift_seq_locations(n, n->v.JoinedStr.values, lineno, col_offset);

break;

case FormattedValue_kind:

shift_expr(n, n->v.FormattedValue.value, lineno, col_offset);

if (n->v.FormattedValue.format_spec) {

shift_expr(n, n->v.FormattedValue.format_spec, lineno, col_offset);

}

break;

default:

return;

}

/* Shift locations for the given node and all its children by adding `lineno`

and `col_offset` to existing locations. Note that n is the already parsed

expression. */

static void fstring_shift_expr_locations(expr_ty n, int lineno, int col_offset)

{

n->col_offset = n->col_offset + col_offset;

// The following is needed, in order for nodes spanning across multiple lines

// to be shifted correctly. An example of such a node is a Call node, the closing

// parenthesis of which is not on the same line as its name.

if (n->lineno == n->end_lineno) {

n->end_col_offset = n->end_col_offset + col_offset;

}

fstring_shift_children_locations(n, lineno, col_offset);

n->lineno = n->lineno + lineno;

n->end_lineno = n->end_lineno + lineno;

}

/* Fix locations for the given node and its children.

`parent` is the enclosing node.

`n` is the node which locations are going to be fixed relative to parent.

`expr_str` is the child node's string representation, including braces.

static void

fstring_fix_expr_location(Token *parent, expr_ty n, char *expr_str)

{

char *substr = NULL;

char *start;

int lines = 0;

int cols = 0;

if (parent && parent->bytes) {

char *parent_str = PyBytes_AsString(parent->bytes);

if (!parent_str) {

return;

}

substr = strstr(parent_str, expr_str);

if (substr) {

// The following is needed, in order to correctly shift the column

// offset, in the case that (disregarding any whitespace) a newline

// immediately follows the opening curly brace of the fstring expression.

int newline_after_brace = 1;

start = substr + 1;

while (start && *start != '}' && *start != '\n') {

if (*start != ' ' && *start != '\t' && *start != '\f') {

newline_after_brace = 0;

break;

}

start++;

}

// Account for the characters from the last newline character to our

// left until the beginning of substr.

if (!newline_after_brace) {

start = substr;

while (start > parent_str && *start != '\n') {

start--;

}

cols += (int)(substr - start);

}

/* adjust the start based on the number of newlines encountered

before the f-string expression */

for (char* p = parent_str; p < substr; p++) {

if (*p == '\n') {

lines++;

}

fstring_shift_expr_locations(n, lines, cols);

}

/* Compile this expression in to an expr_ty. Add parens around the

expression, in order to allow leading spaces in the expression. */

static expr_ty

fstring_compile_expr(Parser *p, const char *expr_start, const char *expr_end,

Token *t)

{

expr_ty expr = NULL;

char *str;

Py_ssize_t len;

const char *s;

expr_ty result = NULL;

assert(expr_end >= expr_start);

assert(*(expr_start-1) == '{');

assert(*expr_end == '}' || *expr_end == '!' || *expr_end == ':' ||

*expr_end == '=');

/* If the substring is all whitespace, it's an error. We need to catch this

here, and not when we call PyParser_SimpleParseStringFlagsFilename,

because turning the expression '' in to '()' would go from being invalid

to valid. */

for (s = expr_start; s != expr_end; s++) {

char c = *s;

/* The Python parser ignores only the following whitespace

characters (\r already is converted to \n). */

if (!(c == ' ' || c == '\t' || c == '\n' || c == '\f')) {

break;

}

if (s == expr_end) {

RAISE_SYNTAX_ERROR("f-string: empty expression not allowed");

return NULL;

}

len = expr_end - expr_start;

/* Allocate 3 extra bytes: open paren, close paren, null byte. */

str = PyMem_RawMalloc(len + 3);

if (str == NULL) {

PyErr_NoMemory();

return NULL;

}

str[0] = '(';

memcpy(str+1, expr_start, len);

str[len+1] = ')';

str[len+2] = 0;

struct tok_state* tok = PyTokenizer_FromString(str, 1);

if (tok == NULL) {

PyMem_RawFree(str);

return NULL;

}

Py_INCREF(p->tok->filename);

tok->filename = p->tok->filename;

Parser *p2 = _PyPegen_Parser_New(tok, Py_fstring_input, p->flags, p->feature_version,

NULL, p->arena);

p2->starting_lineno = p->starting_lineno + p->tok->first_lineno - 1;

p2->starting_col_offset = p->tok->first_lineno == p->tok->lineno

? p->starting_col_offset + t->col_offset : 0;

expr = _PyPegen_run_parser(p2);

if (expr == NULL) {

goto exit;

}

/* Reuse str to find the correct column offset. */

str[0] = '{';

str[len+1] = '}';

fstring_fix_expr_location(t, expr, str);

result = expr;

exit:

PyMem_RawFree(str);

_PyPegen_Parser_Free(p2);

PyTokenizer_Free(tok);

return result;

}

/* Return -1 on error.

Return 0 if we reached the end of the literal.

Return 1 if we haven't reached the end of the literal, but we want

the caller to process the literal up to this point. Used for

doubled braces.

static int

fstring_find_literal(Parser *p, const char **str, const char *end, int raw,

PyObject **literal, int recurse_lvl, Token *t)

{

/* Get any literal string. It ends when we hit an un-doubled left

brace (which isn't part of a unicode name escape such as

"\N{EULER CONSTANT}"), or the end of the string. */

const char *s = *str;

const char *literal_start = s;

int result = 0;

assert(*literal == NULL);

while (s < end) {

char ch = *s++;

if (!raw && ch == '\\' && s < end) {

ch = *s++;

if (ch == 'N') {

if (s < end && *s++ == '{') {

while (s < end && *s++ != '}') {

}

continue;

}

break;

}

if (ch == '{' && warn_invalid_escape_sequence(p, ch, t) < 0) {

return -1;

}

if (ch == '{' || ch == '}') {

/* Check for doubled braces, but only at the top level. If

we checked at every level, then f'{0:{3}}' would fail

with the two closing braces. */

if (recurse_lvl == 0) {

if (s < end && *s == ch) {

/* We're going to tell the caller that the literal ends

here, but that they should continue scanning. But also

skip over the second brace when we resume scanning. */

*str = s + 1;

result = 1;

goto done;

}

/* Where a single '{' is the start of a new expression, a

single '}' is not allowed. */

if (ch == '}') {

*str = s - 1;

RAISE_SYNTAX_ERROR("f-string: single '}' is not allowed");

return -1;

}

/* We're either at a '{', which means we're starting another

expression; or a '}', which means we're at the end of this

f-string (for a nested format_spec). */

s--;

break;

}

*str = s;

assert(s <= end);

assert(s == end || *s == '{' || *s == '}');

done:

if (literal_start != s) {

if (raw)

*literal = PyUnicode_DecodeUTF8Stateful(literal_start,

s - literal_start,

NULL, NULL);

else

*literal = decode_unicode_with_escapes(p, literal_start,

s - literal_start, t);

if (!*literal)

return -1;

}

return result;

}

/* Forward declaration because parsing is recursive. */

static expr_ty

fstring_parse(Parser *p, const char **str, const char *end, int raw, int recurse_lvl,

Token *first_token, Token* t, Token *last_token);

/* Parse the f-string at *str, ending at end. We know *str starts an

expression (so it must be a '{'). Returns the FormattedValue node, which

includes the expression, conversion character, format_spec expression, and

optionally the text of the expression (if = is used).

Note that I don't do a perfect job here: I don't make sure that a

closing brace doesn't match an opening paren, for example. It

doesn't need to error on all invalid expressions, just correctly

find the end of all valid ones. Any errors inside the expression

will be caught when we parse it later.

*expression is set to the expression. For an '=' "debug" expression,

*expr_text is set to the debug text (the original text of the expression,

including the '=' and any whitespace around it, as a string object). If

not a debug expression, *expr_text set to NULL. */

static int

fstring_find_expr(Parser *p, const char **str, const char *end, int raw, int recurse_lvl,

PyObject **expr_text, expr_ty *expression, Token *first_token,

Token *t, Token *last_token)

{

/* Return -1 on error, else 0. */

const char *expr_start;

const char *expr_end;

expr_ty simple_expression;

expr_ty format_spec = NULL; /* Optional format specifier. */

int conversion = -1; /* The conversion char. Use default if not

specified, or !r if using = and no format

spec. */

/* 0 if we're not in a string, else the quote char we're trying to

match (single or double quote). */

char quote_char = 0;

/* If we're inside a string, 1=normal, 3=triple-quoted. */

int string_type = 0;

/* Keep track of nesting level for braces/parens/brackets in

expressions. */

Py_ssize_t nested_depth = 0;

char parenstack[MAXLEVEL];

*expr_text = NULL;

/* Can only nest one level deep. */

if (recurse_lvl >= 2) {

RAISE_SYNTAX_ERROR("f-string: expressions nested too deeply");

goto error;

}

/* The first char must be a left brace, or we wouldn't have gotten

here. Skip over it. */

assert(**str == '{');

*str += 1;

expr_start = *str;

for (; *str < end; (*str)++) {

char ch;

/* Loop invariants. */

assert(nested_depth >= 0);

assert(*str >= expr_start && *str < end);

if (quote_char)

assert(string_type == 1 || string_type == 3);

else

assert(string_type == 0);

ch = **str;

/* Nowhere inside an expression is a backslash allowed. */

if (ch == '\\') {

/* Error: can't include a backslash character, inside

parens or strings or not. */

RAISE_SYNTAX_ERROR(

"f-string expression part "

"cannot include a backslash");

goto error;

}

if (quote_char) {

/* We're inside a string. See if we're at the end. */

/* This code needs to implement the same non-error logic

as tok_get from tokenizer.c, at the letter_quote

label. To actually share that code would be a

nightmare. But, it's unlikely to change and is small,

so duplicate it here. Note we don't need to catch all

of the errors, since they'll be caught when parsing the

expression. We just need to match the non-error

cases. Thus we can ignore \n in single-quoted strings,

for example. Or non-terminated strings. */

if (ch == quote_char) {

/* Does this match the string_type (single or triple

quoted)? */

if (string_type == 3) {

if (*str+2 < end && *(*str+1) == ch && *(*str+2) == ch) {

/* We're at the end of a triple quoted string. */

*str += 2;

string_type = 0;

quote_char = 0;

continue;

}

} else {

/* We're at the end of a normal string. */

quote_char = 0;

string_type = 0;

continue;

}

} else if (ch == '\'' || ch == '"') {

/* Is this a triple quoted string? */

if (*str+2 < end && *(*str+1) == ch && *(*str+2) == ch) {

string_type = 3;

*str += 2;

} else {

/* Start of a normal string. */

string_type = 1;

}

/* Start looking for the end of the string. */

quote_char = ch;

} else if (ch == '[' || ch == '{' || ch == '(') {

if (nested_depth >= MAXLEVEL) {

RAISE_SYNTAX_ERROR("f-string: too many nested parenthesis");

goto error;

}

parenstack[nested_depth] = ch;

nested_depth++;

} else if (ch == '#') {

/* Error: can't include a comment character, inside parens

or not. */

RAISE_SYNTAX_ERROR("f-string expression part cannot include '#'");

goto error;

} else if (nested_depth == 0 &&

(ch == '!' || ch == ':' || ch == '}' ||

ch == '=' || ch == '>' || ch == '<')) {

/* See if there's a next character. */

if (*str+1 < end) {

char next = *(*str+1);

/* For "!=". since '=' is not an allowed conversion character,

nothing is lost in this test. */

if ((ch == '!' && next == '=') || /* != */

(ch == '=' && next == '=') || /* == */

(ch == '<' && next == '=') || /* <= */

(ch == '>' && next == '=') /* >= */

) {

*str += 1;

continue;

}

/* Don't get out of the loop for these, if they're single

chars (not part of 2-char tokens). If by themselves, they

don't end an expression (unlike say '!'). */

if (ch == '>' || ch == '<') {

continue;

}

/* Normal way out of this loop. */

break;

} else if (ch == ']' || ch == '}' || ch == ')') {

if (!nested_depth) {

RAISE_SYNTAX_ERROR("f-string: unmatched '%c'", ch);

goto error;

}

nested_depth--;

int opening = parenstack[nested_depth];

if (!((opening == '(' && ch == ')') ||

(opening == '[' && ch == ']') ||

(opening == '{' && ch == '}')))

{

RAISE_SYNTAX_ERROR(

"f-string: closing parenthesis '%c' "

"does not match opening parenthesis '%c'",

ch, opening);

goto error;

}

} else {

/* Just consume this char and loop around. */

}

expr_end = *str;

/* If we leave this loop in a string or with mismatched parens, we

don't care. We'll get a syntax error when compiling the

expression. But, we can produce a better error message, so

let's just do that.*/

if (quote_char) {

RAISE_SYNTAX_ERROR("f-string: unterminated string");

goto error;

}

if (nested_depth) {

int opening = parenstack[nested_depth - 1];

RAISE_SYNTAX_ERROR("f-string: unmatched '%c'", opening);

goto error;

}

if (*str >= end)

goto unexpected_end_of_string;

/* Compile the expression as soon as possible, so we show errors

related to the expression before errors related to the

conversion or format_spec. */

simple_expression = fstring_compile_expr(p, expr_start, expr_end, t);

if (!simple_expression)

goto error;

/* Check for =, which puts the text value of the expression in

expr_text. */

if (**str == '=') {

if (p->feature_version < 8) {

RAISE_SYNTAX_ERROR("f-string: self documenting expressions are "

"only supported in Python 3.8 and greater");

goto error;

}

*str += 1;

/* Skip over ASCII whitespace. No need to test for end of string

here, since we know there's at least a trailing quote somewhere

ahead. */

while (Py_ISSPACE(**str)) {

*str += 1;

}

/* Set *expr_text to the text of the expression. */

*expr_text = PyUnicode_FromStringAndSize(expr_start, *str-expr_start);

if (!*expr_text) {

goto error;

}

/* Check for a conversion char, if present. */

if (**str == '!') {

*str += 1;

if (*str >= end)

goto unexpected_end_of_string;

conversion = **str;

*str += 1;

/* Validate the conversion. */

if (!(conversion == 's' || conversion == 'r' || conversion == 'a')) {

RAISE_SYNTAX_ERROR(

"f-string: invalid conversion character: "

"expected 's', 'r', or 'a'");

goto error;

}

/* Check for the format spec, if present. */

if (*str >= end)

goto unexpected_end_of_string;

if (**str == ':') {

*str += 1;

if (*str >= end)

goto unexpected_end_of_string;

/* Parse the format spec. */

format_spec = fstring_parse(p, str, end, raw, recurse_lvl+1,

first_token, t, last_token);

if (!format_spec)

goto error;

}

if (*str >= end || **str != '}')

goto unexpected_end_of_string;

/* We're at a right brace. Consume it. */

assert(*str < end);

assert(**str == '}');

*str += 1;

/* If we're in = mode (detected by non-NULL expr_text), and have no format

spec and no explicit conversion, set the conversion to 'r'. */

View remainder of file in raw view

cpython/Parser/string_parser.c at autoconf-config-update · python-emscripten/cpython · GitHub

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