Issue #5067: improve some json error messages.

Patch by Serhiy Storchaka.

Doc/library/json.rst

@@ -99,7 +99,7 @@ Using json.tool from the shell to validate and pretty-print::
         "json": "obj"
     }
     $ echo '{1.2:3.4}' | python -mjson.tool
-    Expecting property name: line 1 column 1 (char 1)
+    Expecting property name enclosed in double quotes: line 1 column 1 (char 1)
 
 .. highlight:: python3
 

Lib/json/__init__.py

@@ -97,7 +97,7 @@ Using json.tool from the shell to validate and pretty-print::
         "json": "obj"
     }
     $ echo '{ 1.2:3.4}' | python -m json.tool
-    Expecting property name: line 1 column 2 (char 2)
+    Expecting property name enclosed in double quotes: line 1 column 2 (char 2)
 """
 __version__ = '2.0.9'
 __all__ = [

Lib/json/decoder.py

@@ -172,7 +172,8 @@ def JSONObject(s_and_end, strict, scan_once, object_hook, object_pairs_hook,
                 pairs = object_hook(pairs)
             return pairs, end + 1
         elif nextchar != '"':
-            raise ValueError(errmsg("Expecting property name", s, end))
+            raise ValueError(errmsg(
+                "Expecting property name enclosed in double quotes", s, end))
     end += 1
     while True:
         key, end = scanstring(s, end, strict)
@@ -182,7 +183,7 @@ def JSONObject(s_and_end, strict, scan_once, object_hook, object_pairs_hook,
         if s[end:end + 1] != ':':
             end = _w(s, end).end()
             if s[end:end + 1] != ':':
-                raise ValueError(errmsg("Expecting : delimiter", s, end))
+                raise ValueError(errmsg("Expecting ':' delimiter", s, end))
         end += 1
 
         try:
@@ -210,12 +211,13 @@ def JSONObject(s_and_end, strict, scan_once, object_hook, object_pairs_hook,
         if nextchar == '}':
             break
         elif nextchar != ',':
-            raise ValueError(errmsg("Expecting , delimiter", s, end - 1))
+            raise ValueError(errmsg("Expecting ',' delimiter", s, end - 1))
         end = _w(s, end).end()
         nextchar = s[end:end + 1]
         end += 1
         if nextchar != '"':
-            raise ValueError(errmsg("Expecting property name", s, end - 1))
+            raise ValueError(errmsg(
+                "Expecting property name enclosed in double quotes", s, end - 1))
     if object_pairs_hook is not None:
         result = object_pairs_hook(pairs)
         return result, end
@@ -249,7 +251,7 @@ def JSONArray(s_and_end, scan_once, _w=WHITESPACE.match, _ws=WHITESPACE_STR):
         if nextchar == ']':
             break
         elif nextchar != ',':
-            raise ValueError(errmsg("Expecting , delimiter", s, end))
+            raise ValueError(errmsg("Expecting ',' delimiter", s, end))
         try:
             if s[end] in _ws:
                 end += 1

Lib/json/tool.py

@@ -7,7 +7,7 @@ Usage::
         "json": "obj"
     }
     $ echo '{ 1.2:3.4}' | python -m json.tool
-    Expecting property name: line 1 column 2 (char 2)
+    Expecting property name enclosed in double quotes: line 1 column 2 (char 2)
 
 """
 import sys

Modules/_json.c

@@ -646,7 +646,7 @@ _parse_object_unicode(PyScannerObject *s, PyObject *pystr, Py_ssize_t idx, Py_ss
 
             /* read key */
             if (PyUnicode_READ(kind, str, idx) != '"') {
-                raise_errmsg("Expecting property name", pystr, idx);
+                raise_errmsg("Expecting property name enclosed in double quotes", pystr, idx);
                 goto bail;
             }
             key = scanstring_unicode(pystr, idx + 1, strict, &next_idx);
@@ -667,7 +667,7 @@ _parse_object_unicode(PyScannerObject *s, PyObject *pystr, Py_ssize_t idx, Py_ss
             /* skip whitespace between key and : delimiter, read :, skip whitespace */
             while (idx <= end_idx && IS_WHITESPACE(PyUnicode_READ(kind, str, idx))) idx++;
             if (idx > end_idx || PyUnicode_READ(kind, str, idx) != ':') {
-                raise_errmsg("Expecting : delimiter", pystr, idx);
+                raise_errmsg("Expecting ':' delimiter", pystr, idx);
                 goto bail;
             }
             idx++;
@@ -707,7 +707,7 @@ _parse_object_unicode(PyScannerObject *s, PyObject *pystr, Py_ssize_t idx, Py_ss
                 break;
             }
             else if (PyUnicode_READ(kind, str, idx) != ',') {
-                raise_errmsg("Expecting , delimiter", pystr, idx);
+                raise_errmsg("Expecting ',' delimiter", pystr, idx);
                 goto bail;
             }
             idx++;
@@ -797,7 +797,7 @@ _parse_array_unicode(PyScannerObject *s, PyObject *pystr, Py_ssize_t idx, Py_ssi
                 break;
             }
             else if (PyUnicode_READ(kind, str, idx) != ',') {
-                raise_errmsg("Expecting , delimiter", pystr, idx);
+                raise_errmsg("Expecting ',' delimiter", pystr, idx);
                 goto bail;
             }
             idx++;