zclsyntax: permit dashes in identifiers

While this does create some ambiguity with arithmetic on variables, like
a-b, this is permitted by HCL and so we'll permit it for zcl too, at the
expense of requiring spaces to be used around minus signs for correct
interpretation.

zcl/zclsyntax/scan_tokens.rl

@@ -34,7 +34,7 @@ func scanTokens(data []byte, filename string, start zcl.Pos, mode scanMode) []To
         BrokenUTF8 = any - AnyUTF8;
 
         NumberLit = digit (digit|'.'|('e'|'E') ('+'|'-')? digit)*;
-        Ident = ID_Start ID_Continue*;
+        Ident = ID_Start (ID_Continue | '-')*;
 
         # Symbols that just represent themselves are handled as a single rule.
         SelfToken = "[" | "]" | "(" | ")" | "." | "," | "*" | "/" | "+" | "-" | "=" | "<" | ">" | "!" | "?" | ":" | "\n" | "&" | "|" | "~" | "^" | ";" | "`";

zcl/zclsyntax/spec.md

@@ -96,7 +96,7 @@ their syntax is defined in terms of the `ID_Start` and `ID_Continue`
 character properties as follows:
 
 ```ebnf
-Identifier = ID_Start ID_Continue*;
+Identifier = ID_Start (ID_Continue | '-')*;
 ```
 
 The Unicode specification provides the normative requirements for identifier
@@ -104,6 +104,11 @@ parsing. Non-normatively, the spirit of this specification is that `ID_Start`
 consists of Unicode letter and certain unambiguous punctuation tokens, while
 `ID_Continue` augments that set with Unicode digits, combining marks, etc.
 
+The dash character `-` is additionally allowed in identifiers, even though
+that is not part of the unicode `ID_Continue` definition. This is to allow
+attribute names and block type names to contain dashes, although underscores
+as word separators are considered the idiomatic usage.
+
 [UAX31]: http://unicode.org/reports/tr31/ "Unicode Identifier and Pattern Syntax"
 
 ### Keywords

zclwrite/format_test.go

@@ -32,24 +32,24 @@ func TestFormat(t *testing.T) {
 			`(a + 2)`,
 		},
 		{
-			`( a-2 )`,
-			`(a - 2)`,
+			`( a*2 )`,
+			`(a * 2)`,
 		},
 		{
 			`( a+-2 )`,
 			`(a + -2)`,
 		},
 		{
-			`( a--2 )`,
-			`(a - -2)`,
+			`( a*-2 )`,
+			`(a * -2)`,
 		},
 		{
 			`(-2+1)`,
 			`(-2 + 1)`,
 		},
 		{
-			`foo(1, -2,a-b, b,c)`,
-			`foo(1, -2, a - b, b, c)`,
+			`foo(1, -2,a*b, b,c)`,
+			`foo(1, -2, a * b, b, c)`,
 		},
 		{
 			`a="hello ${ name }"`,
@@ -80,7 +80,7 @@ hello
 foo(
 1,
 - 2,
-a-b,
+a*b,
 b,
 c,
 )
@@ -89,7 +89,7 @@ c,
 foo(
   1,
   -2,
-  a - b,
+  a * b,
   b,
   c,
 )