Cosmetic changes for jsonpath_gram.y and jsonpath_scan.l

This commit include formatting improvements, renamings and comments.  Also,
it makes jsonpath_scan.l be more uniform with other our lexers.  Firstly,
states names are renamed to more short alternatives.  Secondly, <INITIAL>
prefix removed from the rules.  Corresponding rules are moved to the tail, so
they would anyway work only in initial state.

Author: Alexander Korotkov
Reviewed-by: John Naylor

src/backend/utils/adt/jsonpath_gram.y

@@ -4,6 +4,8 @@
  * jsonpath_gram.y
  *	 Grammar definitions for jsonpath datatype
  *
+ * Transforms tokenized jsonpath into tree of JsonPathParseItem structs.
+ *
  * Copyright (c) 2019, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
@@ -37,15 +39,17 @@ int	jsonpath_yylex(union YYSTYPE *yylval_param);
 int	jsonpath_yyparse(JsonPathParseResult **result);
 void jsonpath_yyerror(JsonPathParseResult **result, const char *message);
 
-static JsonPathParseItem *makeItemType(int type);
+static JsonPathParseItem *makeItemType(JsonPathItemType type);
 static JsonPathParseItem *makeItemString(JsonPathString *s);
 static JsonPathParseItem *makeItemVariable(JsonPathString *s);
 static JsonPathParseItem *makeItemKey(JsonPathString *s);
 static JsonPathParseItem *makeItemNumeric(JsonPathString *s);
 static JsonPathParseItem *makeItemBool(bool val);
-static JsonPathParseItem *makeItemBinary(int type, JsonPathParseItem *la,
+static JsonPathParseItem *makeItemBinary(JsonPathItemType type,
+										 JsonPathParseItem *la,
 										 JsonPathParseItem *ra);
-static JsonPathParseItem *makeItemUnary(int type, JsonPathParseItem *a);
+static JsonPathParseItem *makeItemUnary(JsonPathItemType type,
+										JsonPathParseItem *a);
 static JsonPathParseItem *makeItemList(List *list);
 static JsonPathParseItem *makeIndexArray(List *list);
 static JsonPathParseItem *makeAny(int first, int last);
@@ -170,7 +174,8 @@ predicate:
 	| predicate AND_P predicate		{ $$ = makeItemBinary(jpiAnd, $1, $3); }
 	| predicate OR_P predicate		{ $$ = makeItemBinary(jpiOr, $1, $3); }
 	| NOT_P delimited_predicate 	{ $$ = makeItemUnary(jpiNot, $2); }
-	| '(' predicate ')' IS_P UNKNOWN_P	{ $$ = makeItemUnary(jpiIsUnknown, $2); }
+	| '(' predicate ')' IS_P UNKNOWN_P
+									{ $$ = makeItemUnary(jpiIsUnknown, $2); }
 	| expr STARTS_P WITH_P starts_with_initial
 									{ $$ = makeItemBinary(jpiStartsWith, $1, $4); }
 	| expr LIKE_REGEX_P STRING_P 	{ $$ = makeItemLikeRegex($1, &$3, NULL); }
@@ -232,7 +237,8 @@ any_level:
 any_path:
 	ANY_P							{ $$ = makeAny(0, -1); }
 	| ANY_P '{' any_level '}'		{ $$ = makeAny($3, $3); }
-	| ANY_P '{' any_level TO_P any_level '}'	{ $$ = makeAny($3, $5); }
+	| ANY_P '{' any_level TO_P any_level '}'
+									{ $$ = makeAny($3, $5); }
 	;
 
 accessor_op:
@@ -285,10 +291,15 @@ method:
 	;
 %%
 
-static JsonPathParseItem*
-makeItemType(int type)
+/*
+ * The helper functions below allocate and fill JsonPathParseItem's of various
+ * types.
+ */
+
+static JsonPathParseItem *
+makeItemType(JsonPathItemType type)
 {
-	JsonPathParseItem* v = palloc(sizeof(*v));
+	JsonPathParseItem  *v = palloc(sizeof(*v));
 
 	CHECK_FOR_INTERRUPTS();
 
@@ -298,7 +309,7 @@ makeItemType(int type)
 	return v;
 }
 
-static JsonPathParseItem*
+static JsonPathParseItem *
 makeItemString(JsonPathString *s)
 {
 	JsonPathParseItem  *v;
@@ -364,7 +375,7 @@ makeItemBool(bool val)
 }
 
 static JsonPathParseItem *
-makeItemBinary(int type, JsonPathParseItem* la, JsonPathParseItem *ra)
+makeItemBinary(JsonPathItemType type, JsonPathParseItem *la, JsonPathParseItem *ra)
 {
 	JsonPathParseItem  *v = makeItemType(type);
 
@@ -375,7 +386,7 @@ makeItemBinary(int type, JsonPathParseItem* la, JsonPathParseItem *ra)
 }
 
 static JsonPathParseItem *
-makeItemUnary(int type, JsonPathParseItem* a)
+makeItemUnary(JsonPathItemType type, JsonPathParseItem *a)
 {
 	JsonPathParseItem  *v;
 
@@ -401,7 +412,8 @@ makeItemUnary(int type, JsonPathParseItem* a)
 static JsonPathParseItem *
 makeItemList(List *list)
 {
-	JsonPathParseItem *head, *end;
+	JsonPathParseItem  *head,
+					   *end;
 	ListCell		   *cell = list_head(list);
 
 	head = end = (JsonPathParseItem *) lfirst(cell);
@@ -510,4 +522,12 @@ makeItemLikeRegex(JsonPathParseItem *expr, JsonPathString *pattern,
 	return v;
 }
 
+/*
+ * jsonpath_scan.l is compiled as part of jsonpath_gram.y.  Currently, this is
+ * unavoidable because jsonpath_gram does not create a .h file to export its
+ * token symbols.  If these files ever grow large enough to be worth compiling
+ * separately, that could be fixed; but for now it seems like useless
+ * complication.
+ */
+
 #include "jsonpath_scan.c"