terraform/config/expr.y

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// This is the yacc input for creating the parser for interpolation
// expressions in Go.
// To build it:
//
// go tool yacc -p "expr" expr.y (produces y.go)
//
%{
package config
import (
"fmt"
)
%}
%union {
expr Interpolation
str string
variable InterpolatedVariable
args []Interpolation
}
%type <args> args
%type <expr> expr
%type <str> string
%type <variable> variable
%token <str> STRING IDENTIFIER
%token <str> COMMA LEFTPAREN RIGHTPAREN
%%
top:
expr
{
exprResult = $1
}
expr:
string
{
$$ = &LiteralInterpolation{Literal: $1}
}
| variable
{
$$ = &VariableInterpolation{Variable: $1}
}
| IDENTIFIER LEFTPAREN args RIGHTPAREN
{
f, ok := Funcs[$1]
if !ok {
exprErrors = append(exprErrors, fmt.Errorf(
"Unknown function: %s", $1))
}
$$ = &FunctionInterpolation{Func: f, Args: $3}
}
args:
{
$$ = nil
}
| args COMMA expr
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{
$$ = append($1, $3)
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}
| expr
{
$$ = append($$, $1)
}
string:
STRING
{
$$ = $1
}
variable:
IDENTIFIER
{
var err error
$$, err = NewInterpolatedVariable($1)
if err != nil {
exprErrors = append(exprErrors, fmt.Errorf(
"Error parsing variable '%s': %s", $1, err))
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}
}
%%