Restrict some cases in parsing numerics in jsonpath

Jsonpath now accepts integers with leading zeroes and floats starting with
a dot.  However, SQL standard requires to follow JSON specification, which
doesn't allow none of these cases.  Our json[b] datatypes also restrict that.
So, restrict it in jsonpath altogether.

Author: Nikita Glukhov

src/backend/utils/adt/jsonpath_scan.l

@@ -80,9 +80,9 @@ any			[^\?\%\$\.\[\]\{\}\(\)\|\&\!\=\<\>\@\#\,\*:\-\+\/\\\"\' \t\n\r\f]
 blank		[ \t\n\r\f]
 
 digit		[0-9]
-integer		{digit}+
+integer		(0|[1-9]{digit}*)
-decimal		{digit}*\.{digit}+
+decimal		{integer}\.{digit}+
-decimalfail	{digit}+\.
+decimalfail	{integer}\.
 real		({integer}|{decimal})[Ee][-+]?{digit}+
 realfail1	({integer}|{decimal})[Ee]
 realfail2	({integer}|{decimal})[Ee][-+]

src/test/regress/expected/jsonpath.out

@@ -547,23 +547,20 @@ select '$ ? (@.a < +1)'::jsonpath;
 (1 row)
 
 select '$ ? (@.a < .1)'::jsonpath;
-    jsonpath     
+ERROR:  bad jsonpath representation
------------------
+LINE 1: select '$ ? (@.a < .1)'::jsonpath;
- $?(@."a" < 0.1)
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected '.' at or near "."
-
 select '$ ? (@.a < -.1)'::jsonpath;
-     jsonpath     
+ERROR:  bad jsonpath representation
-------------------
+LINE 1: select '$ ? (@.a < -.1)'::jsonpath;
- $?(@."a" < -0.1)
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected '.' at or near "."
-
 select '$ ? (@.a < +.1)'::jsonpath;
-    jsonpath     
+ERROR:  bad jsonpath representation
------------------
+LINE 1: select '$ ? (@.a < +.1)'::jsonpath;
- $?(@."a" < 0.1)
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected '.' at or near "."
-
 select '$ ? (@.a < 0.1)'::jsonpath;
     jsonpath     
 -----------------
@@ -619,23 +616,20 @@ select '$ ? (@.a < +1e1)'::jsonpath;
 (1 row)
 
 select '$ ? (@.a < .1e1)'::jsonpath;
-   jsonpath    
+ERROR:  bad jsonpath representation
----------------
+LINE 1: select '$ ? (@.a < .1e1)'::jsonpath;
- $?(@."a" < 1)
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected '.' at or near "."
-
 select '$ ? (@.a < -.1e1)'::jsonpath;
-    jsonpath    
+ERROR:  bad jsonpath representation
-----------------
+LINE 1: select '$ ? (@.a < -.1e1)'::jsonpath;
- $?(@."a" < -1)
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected '.' at or near "."
-
 select '$ ? (@.a < +.1e1)'::jsonpath;
-   jsonpath    
+ERROR:  bad jsonpath representation
----------------
+LINE 1: select '$ ? (@.a < +.1e1)'::jsonpath;
- $?(@."a" < 1)
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected '.' at or near "."
-
 select '$ ? (@.a < 0.1e1)'::jsonpath;
    jsonpath    
 ---------------
@@ -691,23 +685,20 @@ select '$ ? (@.a < +1e-1)'::jsonpath;
 (1 row)
 
 select '$ ? (@.a < .1e-1)'::jsonpath;
-     jsonpath     
+ERROR:  bad jsonpath representation
-------------------
+LINE 1: select '$ ? (@.a < .1e-1)'::jsonpath;
- $?(@."a" < 0.01)
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected '.' at or near "."
-
 select '$ ? (@.a < -.1e-1)'::jsonpath;
-     jsonpath      
+ERROR:  bad jsonpath representation
--------------------
+LINE 1: select '$ ? (@.a < -.1e-1)'::jsonpath;
- $?(@."a" < -0.01)
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected '.' at or near "."
-
 select '$ ? (@.a < +.1e-1)'::jsonpath;
-     jsonpath     
+ERROR:  bad jsonpath representation
-------------------
+LINE 1: select '$ ? (@.a < +.1e-1)'::jsonpath;
- $?(@."a" < 0.01)
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected '.' at or near "."
-
 select '$ ? (@.a < 0.1e-1)'::jsonpath;
      jsonpath     
 ------------------
@@ -763,23 +754,20 @@ select '$ ? (@.a < +1e+1)'::jsonpath;
 (1 row)
 
 select '$ ? (@.a < .1e+1)'::jsonpath;
-   jsonpath    
+ERROR:  bad jsonpath representation
----------------
+LINE 1: select '$ ? (@.a < .1e+1)'::jsonpath;
- $?(@."a" < 1)
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected '.' at or near "."
-
 select '$ ? (@.a < -.1e+1)'::jsonpath;
-    jsonpath    
+ERROR:  bad jsonpath representation
-----------------
+LINE 1: select '$ ? (@.a < -.1e+1)'::jsonpath;
- $?(@."a" < -1)
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected '.' at or near "."
-
 select '$ ? (@.a < +.1e+1)'::jsonpath;
-   jsonpath    
+ERROR:  bad jsonpath representation
----------------
+LINE 1: select '$ ? (@.a < +.1e+1)'::jsonpath;
- $?(@."a" < 1)
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected '.' at or near "."
-
 select '$ ? (@.a < 0.1e+1)'::jsonpath;
    jsonpath    
 ---------------
@@ -823,11 +811,10 @@ select '0'::jsonpath;
 (1 row)
 
 select '00'::jsonpath;
- jsonpath 
+ERROR:  bad jsonpath representation
-----------
+LINE 1: select '00'::jsonpath;
- 0
+               ^
-(1 row)
+DETAIL:  syntax error, unexpected IDENT_P at end of input
-
 select '0.0'::jsonpath;
  jsonpath 
 ----------