Enhance error reporting

This patch adds two new fields to the json_error_t struct: column and
source. It also adds functions to populate json_error_t internally.

The column field is not currently used, but it will be utilized in the
decoder and pack/unpack functions.

7 files changed, 129 insertions, 91 deletions

diff --git a/doc/apiref.rst b/doc/apiref.rst
index cabdd10..7408bbb 100644
--- a/doc/apiref.rst
+++ b/doc/apiref.rst
@@ -701,14 +701,24 @@ affect especially the behavior of the decoder.
    .. member:: const char *text
 
       The error message (in UTF-8), or an empty string if a message is
-      not available. This is actually a fixed-length character array,
-      but should be considered constant.
+      not available.
 
    .. member:: int line
 
       The line number on which the error occurred, or -1 if this
       information is not available.
 
+   .. member:: int column
+
+      The character column on which the error occurred, or -1 if this
+      information is not available.
+
+   .. member:: const char *source
+
+      Source of the error. This is (a part of) the file name when
+      using :func:`json_load_file()`, or a special identifier in angle
+      brackets otherwise (e.g. ``<string>``).
+
    The normal use of :type:`json_error_t` is to allocate it on the
    stack, and pass a pointer to a decoding function. Example::
 
diff --git a/src/Makefile.am b/src/Makefile.am
index 659dcb4..be8fcb9 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -3,6 +3,7 @@ include_HEADERS = jansson.h jansson_config.h
 lib_LTLIBRARIES = libjansson.la
 libjansson_la_SOURCES = \
 	dump.c \
+	error.c \
 	hashtable.c \
 	hashtable.h \
 	jansson_private.h \
diff --git a/src/error.c b/src/error.c
new file mode 100644
index 0000000..b8c78db
--- /dev/null
+++ b/src/error.c
@@ -0,0 +1,38 @@
+#include <string.h>
+#include <stdarg.h>
+
+#include "jansson_private.h"
+
+void jsonp_error_init(json_error_t *error, const char *source)
+{
+    if(error)
+    {
+        error->text[0] = '\0';
+        error->line = -1;
+        error->column = -1;
+
+        strncpy(error->source, source, JSON_ERROR_SOURCE_LENGTH);
+        error->source[JSON_ERROR_SOURCE_LENGTH - 1] = '\0';
+    }
+}
+
+void jsonp_error_set(json_error_t *error, int line, int column,
+                     const char *msg, ...)
+{
+    va_list ap;
+
+    if(!error)
+        return;
+
+    if(error->text[0] != '\0') {
+        /* error already set */
+        return;
+    }
+
+    error->line = line;
+    error->column = column;
+
+    va_start(ap, msg);
+    vsnprintf(error->text, JSON_ERROR_TEXT_LENGTH, msg, ap);
+    va_end(ap);
+}
diff --git a/src/jansson.h b/src/jansson.h
index 130dc95..0495418 100644
--- a/src/jansson.h
+++ b/src/jansson.h
@@ -87,11 +87,14 @@ void json_decref(json_t *json)
 
 /* error reporting */
 
-#define JSON_ERROR_TEXT_LENGTH  160
+#define JSON_ERROR_TEXT_LENGTH    160
+#define JSON_ERROR_SOURCE_LENGTH   80
 
 typedef struct {
     char text[JSON_ERROR_TEXT_LENGTH];
     int line;
+    int column;
+    char source[JSON_ERROR_SOURCE_LENGTH];
 } json_error_t;
 
 
diff --git a/src/jansson_private.h b/src/jansson_private.h
index e9102ba..951780c 100644
--- a/src/jansson_private.h
+++ b/src/jansson_private.h
@@ -63,4 +63,8 @@ typedef struct {
 
 const object_key_t *jsonp_object_iter_fullkey(void *iter);
 
+void jsonp_error_init(json_error_t *error, const char *source);
+void jsonp_error_set(json_error_t *error, int line, int column,
+                     const char *msg, ...);
+
 #endif
diff --git a/src/load.c b/src/load.c
index 925a850..f05230b 100644
--- a/src/load.c
+++ b/src/load.c
@@ -60,54 +60,46 @@ typedef struct {
 
 /*** error reporting ***/
 
-static void error_init(json_error_t *error)
-{
-    if(error)
-    {
-        error->text[0] = '\0';
-        error->line = -1;
-    }
-}
-
 static void error_set(json_error_t *error, const lex_t *lex,
                       const char *msg, ...)
 {
     va_list ap;
-    char text[JSON_ERROR_TEXT_LENGTH];
+    char msg_text[JSON_ERROR_TEXT_LENGTH];
 
-    if(!error || error->text[0] != '\0') {
-        /* error already set */
+    int line = -1, col = -1;
+    const char *result = msg_text;
+
+    if(!error)
         return;
-    }
 
     va_start(ap, msg);
-    vsnprintf(text, JSON_ERROR_TEXT_LENGTH, msg, ap);
+    vsnprintf(msg_text, JSON_ERROR_TEXT_LENGTH, msg, ap);
     va_end(ap);
 
     if(lex)
     {
         const char *saved_text = strbuffer_value(&lex->saved_text);
-        error->line = lex->line;
+        char msg_with_context[JSON_ERROR_TEXT_LENGTH];
+
+        line = lex->line;
+
         if(saved_text && saved_text[0])
         {
             if(lex->saved_text.length <= 20) {
-                snprintf(error->text, JSON_ERROR_TEXT_LENGTH,
-                         "%s near '%s'", text, saved_text);
+                snprintf(msg_with_context, JSON_ERROR_TEXT_LENGTH,
+                         "%s near '%s'", msg_text, saved_text);
+                result = msg_with_context;
             }
-            else
-                snprintf(error->text, JSON_ERROR_TEXT_LENGTH, "%s", text);
         }
         else
         {
-            snprintf(error->text, JSON_ERROR_TEXT_LENGTH,
-                     "%s near end of file", text);
+            snprintf(msg_with_context, JSON_ERROR_TEXT_LENGTH,
+                     "%s near end of file", msg_text);
+            result = msg_with_context;
         }
     }
-    else
-    {
-        error->line = -1;
-        snprintf(error->text, JSON_ERROR_TEXT_LENGTH, "%s", text);
-    }
+
+    jsonp_error_set(error, line, col, "%s", result);
 }
 
 
@@ -774,8 +766,6 @@ static json_t *parse_value(lex_t *lex, json_error_t *error)
 
 static json_t *parse_json(lex_t *lex, json_error_t *error)
 {
-    error_init(error);
-
     lex_scan(lex, error);
     if(lex->token != '[' && lex->token != '{') {
         error_set(error, lex, "'[' or '{' expected");
@@ -822,6 +812,8 @@ json_t *json_loads(const char *string, size_t flags, json_error_t *error)
     if(lex_init(&lex, string_get, string_eof, (void *)&stream_data))
         return NULL;
 
+    jsonp_error_init(error, "<string>");
+
     result = parse_json(&lex, error);
     if(!result)
         goto out;
@@ -841,12 +833,20 @@ out:
 json_t *json_loadf(FILE *input, size_t flags, json_error_t *error)
 {
     lex_t lex;
+    const char *source;
     json_t *result;
     (void)flags; /* unused */
 
     if(lex_init(&lex, (get_func)fgetc, (eof_func)feof, input))
         return NULL;
 
+    if(input == stdin)
+        source = "<stdin>";
+    else
+        source = "<stream>";
+
+    jsonp_error_init(error, source);
+
     result = parse_json(&lex, error);
     if(!result)
         goto out;
@@ -868,7 +868,7 @@ json_t *json_load_file(const char *path, size_t flags, json_error_t *error)
     json_t *result;
     FILE *fp;
 
-    error_init(error);
+    jsonp_error_init(error, path);
 
     fp = fopen(path, "r");
     if(!fp)
diff --git a/src/variadic.c b/src/variadic.c
index 7b9c9fc..89ff1da 100644
--- a/src/variadic.c
+++ b/src/variadic.c
@@ -13,31 +13,6 @@
 #include <jansson.h>
 #include "jansson_private.h"
 
-static void error_init(json_error_t *error)
-{
-    if(error)
-    {
-        error->text[0] = '\0';
-        error->line = -1;
-    }
-}
-
-static void error_set(json_error_t *error, const int line, const char *msg, ...)
-{
-    va_list ap;
-
-    if(!error || error->text[0] != '\0') {
-        /* error already set */
-        return;
-    }
-
-    error->line = line;
-
-    va_start(ap, msg);
-    vsnprintf(error->text, JSON_ERROR_TEXT_LENGTH, msg, ap);
-    va_end(ap);
-}
-
 json_t *json_pack(json_error_t *error, const char *fmt, ...) {
     int fmt_length = strlen(fmt);
     va_list ap;
@@ -63,7 +38,7 @@ json_t *json_pack(json_error_t *error, const char *fmt, ...) {
     stack = calloc(fmt_length, sizeof(json_t *));
     free_list = calloc(fmt_length, sizeof(json_t *));
 
-    error_init(error);
+    jsonp_error_init(error, "");
 
     if(!stack || !free_list)
         goto out;
@@ -81,7 +56,7 @@ json_t *json_pack(json_error_t *error, const char *fmt, ...) {
             case ',': /* Element spacer */
                 if(!root)
                 {
-                    error_set(error, line,
+                    jsonp_error_set(error, line, -1,
                               "Unexpected COMMA precedes root element!");
                     root = NULL;
                     goto out;
@@ -89,7 +64,7 @@ json_t *json_pack(json_error_t *error, const char *fmt, ...) {
 
                 if(!cur)
                 {
-                    error_set(error, line,
+                    jsonp_error_set(error, line, -1,
                               "Unexpected COMMA outside a list or object!");
                     root = NULL;
                     goto out;
@@ -97,7 +72,8 @@ json_t *json_pack(json_error_t *error, const char *fmt, ...) {
 
                 if(key)
                 {
-                    error_set(error, line, "Expected KEY, got COMMA!");
+                    jsonp_error_set(error, line, -1,
+                              "Expected KEY, got COMMA!");
                     root = NULL;
                     goto out;
                 }
@@ -106,16 +82,18 @@ json_t *json_pack(json_error_t *error, const char *fmt, ...) {
             case ':': /* Key/value separator */
                 if(!key)
                 {
-                    error_set(error, line, "Got key/value separator without "
-                            "a key preceding it!");
+                    jsonp_error_set(error, line, -1,
+                              "Got key/value separator without "
+                              "a key preceding it!");
                     root = NULL;
                     goto out;
                 }
 
                 if(!json_is_object(cur))
                 {
-                    error_set(error, line, "Got a key/value separator "
-                            "(':') outside an object!");
+                    jsonp_error_set(error, line, -1,
+                              "Got a key/value separator "
+                              "(':') outside an object!");
                     root = NULL;
                     goto out;
                 }
@@ -127,7 +105,8 @@ json_t *json_pack(json_error_t *error, const char *fmt, ...) {
 
                 if(key)
                 {
-                    error_set(error, line, "OBJECT or ARRAY ended with an "
+                    jsonp_error_set(error, line, -1,
+                              "OBJECT or ARRAY ended with an "
                               "incomplete key/value pair!");
                     root = NULL;
                     goto out;
@@ -135,7 +114,7 @@ json_t *json_pack(json_error_t *error, const char *fmt, ...) {
 
                 if(depth <= 0)
                 {
-                    error_set(error, line,
+                    jsonp_error_set(error, line, -1,
                               "Too many close-brackets '%c'", *fmt);
                     root = NULL;
                     goto out;
@@ -143,7 +122,7 @@ json_t *json_pack(json_error_t *error, const char *fmt, ...) {
 
                 if(*fmt == ']' && !json_is_array(cur))
                 {
-                    error_set(error, line,
+                    jsonp_error_set(error, line, -1,
                               "Stray close-array ']' character");
                     root = NULL;
                     goto out;
@@ -151,7 +130,7 @@ json_t *json_pack(json_error_t *error, const char *fmt, ...) {
 
                 if(*fmt == '}' && !json_is_object(cur))
                 {
-                    error_set(error, line,
+                    jsonp_error_set(error, line, -1,
                               "Stray close-object '}' character");
                     root = NULL;
                     goto out;
@@ -173,7 +152,7 @@ json_t *json_pack(json_error_t *error, const char *fmt, ...) {
 
                 if(!s)
                 {
-                    error_set(error, line,
+                    jsonp_error_set(error, line, -1,
                               "Refusing to handle a NULL string");
                     root = NULL;
                     goto out;
@@ -221,8 +200,8 @@ obj_common:     free_list[free_count++] = obj;
                 if(json_is_object(cur)) {
                     if(!key)
                     {
-                        error_set(error, line,
-                                "Expected key, got identifier '%c'!", *fmt);
+                        jsonp_error_set(error, line, -1,
+                              "Expected key, got identifier '%c'!", *fmt);
                         root = NULL;
                         goto out;
                     }
@@ -241,7 +220,8 @@ obj_common:     free_list[free_count++] = obj;
                 }
                 else
                 {
-                    error_set(error, line, "Can't figure out where to attach "
+                    jsonp_error_set(error, line, -1,
+                              "Can't figure out where to attach "
                               "'%c' object!", *fmt);
                     root = NULL;
                     goto out;
@@ -261,7 +241,7 @@ obj_common:     free_list[free_count++] = obj;
     va_end(ap);
 
     if(depth != 0) {
-        error_set(error, line,
+        jsonp_error_set(error, line, -1,
                 "Missing object or array close-brackets in format string");
         root = NULL;
         goto out;
@@ -301,13 +281,13 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
 
     int fmt_length = strlen(fmt);
 
-    error_init(error);
+    jsonp_error_init(error, "");
 
     /* Allocation provisioned for worst case */
     stack = calloc(fmt_length, sizeof(json_t *));
     if(!stack)
     {
-        error_set(error, line, "Out of memory!");
+        jsonp_error_set(error, line, -1, "Out of memory!");
         rv = -1;
         goto out;
     }
@@ -335,7 +315,7 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
 
                 if(!cur)
                 {
-                    error_set(error, line,
+                    jsonp_error_set(error, line, -1,
                               "Unexpected COMMA outside a list or object!");
                     rv = -1;
                     goto out;
@@ -343,7 +323,8 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
 
                 if(key)
                 {
-                    error_set(error, line, "Expected KEY, got COMMA!");
+                    jsonp_error_set(error, line, -1,
+                              "Expected KEY, got COMMA!");
                     rv = -1;
                     goto out;
                 }
@@ -352,7 +333,7 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
             case ':': /* Key/value separator */
                 if(!json_is_object(cur) || !key)
                 {
-                    error_set(error, line, "Unexpected ':'");
+                    jsonp_error_set(error, line, -1, "Unexpected ':'");
                     rv = -1;
                     goto out;
                 }
@@ -369,7 +350,8 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
                 {
                     if(!key)
                     {
-                        error_set(error, line, "Objects can't be keys");
+                        jsonp_error_set(error, line, -1,
+                              "Objects can't be keys");
                         rv = -1;
                         goto out;
                     }
@@ -419,28 +401,28 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
 
                 if(json_is_array(cur) && *fmt!=']')
                 {
-                    error_set(error, line, "Missing ']'");
+                    jsonp_error_set(error, line, -1, "Missing ']'");
                     rv = -1;
                     goto out;
                 }
 
                 if(json_is_object(cur) && *fmt!='}')
                 {
-                    error_set(error, line, "Missing '}'");
+                    jsonp_error_set(error, line, -1, "Missing '}'");
                     rv = -1;
                     goto out;
                 }
 
                 if(key)
                 {
-                    error_set(error, line, "Unexpected '%c'", *fmt);
+                    jsonp_error_set(error, line, -1, "Unexpected '%c'", *fmt);
                     rv = -1;
                     goto out;
                 }
 
                 if(depth <= 0)
                 {
-                    error_set(error, line, "Unexpected '%c'", *fmt);
+                    jsonp_error_set(error, line, -1, "Unexpected '%c'", *fmt);
                     rv = -1;
                     goto out;
                 }
@@ -474,7 +456,7 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
                 {
                     if(!key)
                     {
-                        error_set(error, line,
+                        jsonp_error_set(error, line, -1,
                                   "Only strings may be used as keys!");
                         rv = -1;
                         goto out;
@@ -492,7 +474,7 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
                 }
                 else
                 {
-                    error_set(error, line,
+                    jsonp_error_set(error, line, -1,
                               "Unsure how to retrieve JSON object '%c'",
                               *fmt);
                     rv = -1;
@@ -504,7 +486,7 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
                     case 's':
                         if(!json_is_string(obj))
                         {
-                            error_set(error, line,
+                            jsonp_error_set(error, line, -1,
                                     "Type mismatch! Object wasn't a string.");
                             rv = -2;
                             goto out;
@@ -515,7 +497,7 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
                     case 'i':
                         if(!json_is_integer(obj))
                         {
-                            error_set(error, line,
+                            jsonp_error_set(error, line, -1,
                                     "Type mismatch! Object wasn't an integer.");
                             rv = -2;
                             goto out;
@@ -526,7 +508,7 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
                     case 'b':
                         if(!json_is_boolean(obj))
                         {
-                            error_set(error, line,
+                            jsonp_error_set(error, line, -1,
                                     "Type mismatch! Object wasn't a boolean.");
                             rv = -2;
                             goto out;
@@ -537,7 +519,7 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
                     case 'f':
                         if(!json_is_number(obj))
                         {
-                            error_set(error, line,
+                            jsonp_error_set(error, line, -1,
                                     "Type mismatch! Object wasn't a real.");
                             rv = -2;
                             goto out;
@@ -560,7 +542,7 @@ int json_unpack(json_t *root, json_error_t *error, const char *fmt, ...) {
                         break;
 
                     default:
-                        error_set(error, line,
+                        jsonp_error_set(error, line, -1,
                                 "Unknown format character '%c'", *fmt);
                         rv = -1;
                         goto out;