Skip to content

Commit

Permalink
Revisit error message details for JSON input parsing.
Browse files Browse the repository at this point in the history 
Instead of identifying error locations only by line number (which could
be entirely unhelpful with long input lines), provide a fragment of the
input text too, placing this info in a new CONTEXT entry.  Make the
error detail messages conform more closely to style guidelines, fix
failure to expose some of them for translation, ensure compiler can
check formats against supplied parameters.
  • Loading branch information
@tglsfdc
tglsfdc committed Jun 13, 2012
1 parent 0f0fba1 commit 80edfd7
Show file tree
Hide file tree
Showing 2 changed files with 224 additions and 86 deletions.
211 changes: 161 additions & 50 deletions src/backend/utils/adt/json.c
View file
Expand Up @@ -43,8 +43,6 @@ typedef struct /* state of JSON lexer */
char *token_start; /* start of current token within input */
char *token_terminator; /* end of previous or current token */
JsonValueType token_type; /* type of current token, once it's known */
int line_number; /* current line number (counting from 1) */
char *line_start; /* start of current line within input (BROKEN!!) */
} JsonLexContext;

typedef enum /* states of JSON parser */
Expand Down Expand Up @@ -78,6 +76,7 @@ static void json_lex_string(JsonLexContext *lex);
static void json_lex_number(JsonLexContext *lex, char *s);
static void report_parse_error(JsonParseStack *stack, JsonLexContext *lex);
static void report_invalid_token(JsonLexContext *lex);
static int report_json_context(JsonLexContext *lex);
static char *extract_mb_char(char *s);
static void composite_to_json(Datum composite, StringInfo result,
bool use_line_feeds);
Expand Down Expand Up @@ -185,8 +184,6 @@ json_validate_cstring(char *input)
/* Set up lexing context. */
lex.input = input;
lex.token_terminator = lex.input;
lex.line_number = 1;
lex.line_start = input;

/* Set up parse stack. */
stacksize = 32;
Expand Down Expand Up @@ -335,11 +332,7 @@ json_lex(JsonLexContext *lex)
/* Skip leading whitespace. */
s = lex->token_terminator;
while (*s == ' ' || *s == '\t' || *s == '\n' || *s == '\r')
{
if (*s == '\n')
lex->line_number++;
s++;
}
lex->token_start = s;

/* Determine token type. */
Expand All @@ -350,7 +343,7 @@ json_lex(JsonLexContext *lex)
{
/* End of string. */
lex->token_start = NULL;
lex->token_terminator = NULL;
lex->token_terminator = s;
}
else
{
Expand Down Expand Up @@ -397,7 +390,8 @@ json_lex(JsonLexContext *lex)
/*
* We got some sort of unexpected punctuation or an otherwise
* unexpected character, so just complain about that one
* character.
* character. (It can't be multibyte because the above loop
* will advance over any multibyte characters.)
*/
lex->token_terminator = s + 1;
report_invalid_token(lex);
Expand Down Expand Up @@ -443,11 +437,14 @@ json_lex_string(JsonLexContext *lex)
lex->token_terminator = s;
report_invalid_token(lex);
}
/* Since *s isn't printable, exclude it from the context string */
lex->token_terminator = s;
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json"),
errdetail("line %d: Character with value \"0x%02x\" must be escaped.",
lex->line_number, (unsigned char) *s)));
errdetail("Character with value 0x%02x must be escaped.",
(unsigned char) *s),
report_json_context(lex)));
}
else if (*s == '\\')
{
Expand All @@ -465,38 +462,39 @@ json_lex_string(JsonLexContext *lex)

for (i = 1; i <= 4; i++)
{
if (s[i] == '\0')
s++;
if (*s == '\0')
{
lex->token_terminator = s + i;
lex->token_terminator = s;
report_invalid_token(lex);
}
else if (s[i] >= '0' && s[i] <= '9')
ch = (ch * 16) + (s[i] - '0');
else if (s[i] >= 'a' && s[i] <= 'f')
ch = (ch * 16) + (s[i] - 'a') + 10;
else if (s[i] >= 'A' && s[i] <= 'F')
ch = (ch * 16) + (s[i] - 'A') + 10;
else if (*s >= '0' && *s <= '9')
ch = (ch * 16) + (*s - '0');
else if (*s >= 'a' && *s <= 'f')
ch = (ch * 16) + (*s - 'a') + 10;
else if (*s >= 'A' && *s <= 'F')
ch = (ch * 16) + (*s - 'A') + 10;
else
{
lex->token_terminator = s + pg_mblen(s);
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json"),
errdetail("line %d: \"\\u\" must be followed by four hexadecimal digits.",
lex->line_number)));
errdetail("\"\\u\" must be followed by four hexadecimal digits."),
report_json_context(lex)));
}
}

/* Account for the four additional bytes we just parsed. */
s += 4;
}
else if (strchr("\"\\/bfnrt", *s) == NULL)
{
/* Not a valid string escape, so error out. */
lex->token_terminator = s + pg_mblen(s);
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json"),
errdetail("line %d: Invalid escape \"\\%s\".",
lex->line_number, extract_mb_char(s))));
errdetail("Escape sequence \"\\%s\" is invalid.",
extract_mb_char(s)),
report_json_context(lex)));
}
}
}
Expand Down Expand Up @@ -599,75 +597,116 @@ json_lex_number(JsonLexContext *lex, char *s)

/*
* Report a parse error.
*
* lex->token_start and lex->token_terminator must identify the current token.
*/
static void
report_parse_error(JsonParseStack *stack, JsonLexContext *lex)
{
char *detail = NULL;
char *token = NULL;
char *token;
int toklen;

/* Handle case where the input ended prematurely. */
if (lex->token_start == NULL)
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json: \"%s\"",
lex->input),
errdetail("The input string ended unexpectedly.")));
errmsg("invalid input syntax for type json"),
errdetail("The input string ended unexpectedly."),
report_json_context(lex)));

/* Separate out the offending token. */
/* Separate out the current token. */
toklen = lex->token_terminator - lex->token_start;
token = palloc(toklen + 1);
memcpy(token, lex->token_start, toklen);
token[toklen] = '\0';

/* Select correct detail message. */
/* Complain, with the appropriate detail message. */
if (stack == NULL)
detail = "line %d: Expected end of input, but found \"%s\".";
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json"),
errdetail("Expected end of input, but found \"%s\".",
token),
report_json_context(lex)));
else
{
switch (stack->state)
{
case JSON_PARSE_VALUE:
detail = "line %d: Expected string, number, object, array, true, false, or null, but found \"%s\".";
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json"),
errdetail("Expected JSON value, but found \"%s\".",
token),
report_json_context(lex)));
break;
case JSON_PARSE_ARRAY_START:
detail = "line %d: Expected array element or \"]\", but found \"%s\".";
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json"),
errdetail("Expected array element or \"]\", but found \"%s\".",
token),
report_json_context(lex)));
break;
case JSON_PARSE_ARRAY_NEXT:
detail = "line %d: Expected \",\" or \"]\", but found \"%s\".";
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json"),
errdetail("Expected \",\" or \"]\", but found \"%s\".",
token),
report_json_context(lex)));
break;
case JSON_PARSE_OBJECT_START:
detail = "line %d: Expected string or \"}\", but found \"%s\".";
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json"),
errdetail("Expected string or \"}\", but found \"%s\".",
token),
report_json_context(lex)));
break;
case JSON_PARSE_OBJECT_LABEL:
detail = "line %d: Expected \":\", but found \"%s\".";
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json"),
errdetail("Expected \":\", but found \"%s\".",
token),
report_json_context(lex)));
break;
case JSON_PARSE_OBJECT_NEXT:
detail = "line %d: Expected \",\" or \"}\", but found \"%s\".";
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json"),
errdetail("Expected \",\" or \"}\", but found \"%s\".",
token),
report_json_context(lex)));
break;
case JSON_PARSE_OBJECT_COMMA:
detail = "line %d: Expected string, but found \"%s\".";
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json"),
errdetail("Expected string, but found \"%s\".",
token),
report_json_context(lex)));
break;
default:
elog(ERROR, "unexpected json parse state: %d",
(int) stack->state);
}
}

ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json: \"%s\"",
lex->input),
detail ? errdetail(detail, lex->line_number, token) : 0));
}

/*
* Report an invalid input token.
*
* lex->token_start and lex->token_terminator must identify the token.
*/
static void
report_invalid_token(JsonLexContext *lex)
{
char *token;
int toklen;

/* Separate out the offending token. */
toklen = lex->token_terminator - lex->token_start;
token = palloc(toklen + 1);
memcpy(token, lex->token_start, toklen);
Expand All @@ -676,8 +715,80 @@ report_invalid_token(JsonLexContext *lex)
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for type json"),
errdetail("line %d: Token \"%s\" is invalid.",
lex->line_number, token)));
errdetail("Token \"%s\" is invalid.", token),
report_json_context(lex)));
}

/*
* Report a CONTEXT line for bogus JSON input.
*
* lex->token_terminator must be set to identify the spot where we detected
* the error. Note that lex->token_start might be NULL, in case we recognized
* error at EOF.
*
* The return value isn't meaningful, but we make it non-void so that this
* can be invoked inside ereport().
*/
static int
report_json_context(JsonLexContext *lex)
{
const char *context_start;
const char *context_end;
const char *line_start;
int line_number;
char *ctxt;
int ctxtlen;
const char *prefix;
const char *suffix;

/* Choose boundaries for the part of the input we will display */
context_start = lex->input;
context_end = lex->token_terminator;
line_start = context_start;
line_number = 1;
for (;;)
{
/* Always advance over newlines (context_end test is just paranoia) */
if (*context_start == '\n' && context_start < context_end)
{
context_start++;
line_start = context_start;
line_number++;
continue;
}
/* Otherwise, done as soon as we are close enough to context_end */
if (context_end - context_start < 50)
break;
/* Advance to next multibyte character */
if (IS_HIGHBIT_SET(*context_start))
context_start += pg_mblen(context_start);
else
context_start++;
}

/*
* We add "..." to indicate that the excerpt doesn't start at the
* beginning of the line ... but if we're within 3 characters of the
* beginning of the line, we might as well just show the whole line.
*/
if (context_start - line_start <= 3)
context_start = line_start;

/* Get a null-terminated copy of the data to present */
ctxtlen = context_end - context_start;
ctxt = palloc(ctxtlen + 1);
memcpy(ctxt, context_start, ctxtlen);
ctxt[ctxtlen] = '\0';

/*
* Show the context, prefixing "..." if not starting at start of line, and
* suffixing "..." if not ending at end of line.
*/
prefix = (context_start > line_start) ? "..." : "";
suffix = (*context_end != '\0' && *context_end != '\n' && *context_end != '\r') ? "..." : "";

return errcontext("JSON data, line %d: %s%s%s",
line_number, prefix, ctxt, suffix);
}

/*
Expand Down

0 comments on commit 80edfd7

Please sign in to comment.