Implement function calls

README.md

@@ -48,6 +48,5 @@ Currently, this parser supports all HCL features except:
 
 - [For Expressions](https://github.com/hashicorp/hcl/blob/main/hclsyntax/spec.md#for-expressions)
 - [Templates](https://github.com/hashicorp/hcl/blob/main/hclsyntax/spec.md#templates)
-- [Function Calls](https://github.com/hashicorp/hcl/blob/main/hclsyntax/spec.md#functions-and-function-calls)
 
 Support for these features is planned.

hisscl/ast.py

@@ -30,13 +30,21 @@ class String:
     pos: Position
     value: str
     
+Literal = Integer | Float | Bool | String
+    
 @dataclasses.dataclass
 class VariableRef:
     pos: Position
     name: str
     
-Literal = Integer | Float | Bool | String | VariableRef
+@dataclasses.dataclass
+class FunctionCall:
+    pos: Position
+    name: str
+    args: list['Value']
 
+Ref = VariableRef | FunctionCall
+    
 @dataclasses.dataclass
 class Tuple:
     pos: Position
@@ -67,8 +75,13 @@ class UnaryExpression:
     op: Operator
     value: 'Value'
     
-Expression = BinaryExpression | UnaryExpression
-Value = Literal | Collection | Expression
+@dataclasses.dataclass
+class Expansion:
+    pos: Position
+    value: 'Value'
+    
+Expression = BinaryExpression | UnaryExpression | Expansion
+Value = Literal | Collection | Expression | Ref
 
 @dataclasses.dataclass
 class Assignment:

hisscl/interp.py

@@ -38,6 +38,8 @@ class Interp:
             if val.name not in self.vars:
                 raise KeyError(f'{val.pos}: no such variable: {repr(val.name)}')
             return self.vars[val.name]
+        elif isinstance(val, ast.FunctionCall):
+            return self._exec_func_call(val)
         elif isinstance(val, ast.Literal):
             return val.value
         elif isinstance(val, ast.Tuple):
@@ -48,6 +50,8 @@ class Interp:
             return self._eval_binary_expr(val)
         elif isinstance(val, ast.UnaryExpression):
             return self._eval_unary_expr(val)
+        elif isinstance(val, ast.Expansion):
+            raise ValueError(f'{val.pos}: cannot use expansion operator outside of a function call')
     
     def _is_numerical(self, val: typing.Any) -> bool:
         return isinstance(val, float | int) and type(val) is not bool
@@ -55,6 +59,22 @@ class Interp:
     def _is_comparable(self, val: typing.Any) -> bool:
         return self._is_numerical(val) or isinstance(val, str)
     
+    def _exec_func_call(self, call: ast.FunctionCall) -> typing.Any:
+        if call.name not in self.vars:
+            raise KeyError(f'{call.pos}: no such function: {repr(call.name)}')
+        elif not callable(self.vars[call.name]):
+            raise ValueError(f'{call.pos}: cannot call non-callable object')
+        args = []
+        for arg in call.args:
+            if isinstance(arg, ast.Expansion):
+                val = self._convert_value(arg.value)
+                if not isinstance(val, typing.Iterable):
+                    raise ValueError(f"{arg.pos}: cannot perform expansion on non-iterable value ({type(val).__name__})")
+                args.extend(val)
+            else:
+                args.append(self._convert_value(arg))
+        return self.vars[call.name](*args)
+        
     def _eval_unary_expr(self, expr: ast.UnaryExpression) -> float | int | bool:
         val = self._convert_value(expr.value)
         match expr.op.value:

hisscl/lexer.py

@@ -24,6 +24,7 @@ class Token(enum.Enum):
     COMMA = 11
     COLON = 12
     OPERATOR = 13
+    ELLIPSIS = 14
 
 class ExpectedError(Exception):
     def __init__(self, pos: ast.Position, expected: str, got: str):
@@ -42,6 +43,8 @@ class Lexer:
         self.pos.name = name
 
     def _peek(self, n: int) -> str:
+        if self.unread != '':
+            return self.unread
         pos = self.stream.tell()
         text = self.stream.read(n)
         self.stream.seek(pos)
@@ -226,6 +229,12 @@ class Lexer:
                 # Ignore comments and return next token
                 self._scan_comment(char)
                 return self.scan()
+            case '.':
+                if (next := self._read()) != '.':
+                    raise ExpectedError(self.pos, '.', next)
+                if (next := self._read()) != '.':
+                    raise ExpectedError(self.pos, '.', next)
+                return Token.ELLIPSIS, self.pos, "..."
             case '':
                 return Token.EOF, self.pos, char
 

hisscl/parser.py

@@ -76,6 +76,35 @@ class Parser:
                 self._unscan(tok, pos, lit)
             
         return ast.Object(start_pos, items)
+        
+    def _parse_func_call(self) -> ast.FunctionCall:
+        id_tok, id_pos, id_lit = self._scan()
+        tok, pos, lit = self._scan()
+        if tok != lexer.Token.PAREN or lit != '(':
+            raise ExpectedError(pos, 'opening parentheses', lit)
+        
+        tok, pos, lit = self._scan()
+        if tok == lexer.Token.PAREN and lit == ')':
+            return ast.FunctionCall(pos=id_pos, name=id_lit, args=[])
+        self._unscan(tok, pos, lit)
+        
+        args: list[ast.Value] = []
+        while True:
+            args.append(self._parse_expr())
+            tok, pos, lit = self._scan()
+            if tok == lexer.Token.PAREN and lit == ')':
+                break
+            elif tok == lexer.Token.COMMA:
+                continue
+            elif tok == lexer.Token.ELLIPSIS:
+                args[-1] = ast.Expansion(pos=args[-1].pos, value=args[-1])
+                tok, pos, lit = self._scan()
+                if tok != lexer.Token.PAREN or lit != ')':
+                    raise ExpectedError(pos, 'closing parentheses', lit)
+                break
+            else:
+                raise ExpectedError(pos, 'comma or closing parentheses', lit)
+        return ast.FunctionCall(pos=id_pos, name=id_lit, args=args)
     
     def _parse_value(self) -> ast.Value:
         tok, pos, lit = self._scan()
@@ -89,6 +118,9 @@ class Parser:
             case lexer.Token.STRING:
                 return ast.String(pos=pos, value=pyast.literal_eval(lit))
             case lexer.Token.IDENT:
+                if self.lexer._peek(1) == '(':
+                    self._unscan(tok, pos, lit)
+                    return self._parse_func_call()
                 return ast.VariableRef(pos=pos, name=lit)
             case lexer.Token.HEREDOC:
                 return ast.String(pos=pos, value=lit)