globals will raise an error if defined twice

Author: togglebyte

CHANGES.md

@@ -6,6 +6,7 @@
     * BUGFIX: ctrl+c works with the error display
     * Trying to use a component twice will now include the component name in the
       error
+    * Global definitions will raise an error if it's already assigned
 * 0.2.7
     * BUGFIX: use correct truthiness check in control flow update
 * 0.2.6

anathema-templates/src/error/mod.rs

@@ -54,6 +54,7 @@ pub enum ErrorKind {
     EmptyBody,
     InvalidStatement(String),
     Io(std::io::Error),
+    GlobalAlreadyAssigned(String)
 }
 
 impl ErrorKind {
@@ -72,6 +73,7 @@ impl Display for ErrorKind {
             ErrorKind::EmptyBody => write!(f, "if or else node has no children"),
             ErrorKind::InvalidStatement(stmt) => write!(f, "invalid statement: {stmt}"),
             ErrorKind::Io(err) => write!(f, "{err}"),
+            ErrorKind::GlobalAlreadyAssigned(name) => write!(f, "global value `{name}` already assigned"),
         }
     }
 }

anathema-templates/src/statements/eval.rs

@@ -61,7 +61,10 @@ impl Scope {
                     }
                     match is_global {
                         false => _ = ctx.variables.define_local(binding, value),
-                        true => ctx.variables.define_global(binding, value),
+                        true => match ctx.variables.define_global(binding, value) {
+                            Ok(()) => (),
+                            Err(kind) => return Err(kind.to_error(ctx.template.path())),
+                        }
                     }
                 }
                 Statement::ComponentSlot(slot_id) => {

anathema-templates/src/variables.rs

@@ -2,7 +2,7 @@ use std::collections::HashMap;
 
 use anathema_store::slab::{Slab, SlabIndex};
 
-use crate::expressions::Expression;
+use crate::{error::ErrorKind, expressions::Expression};
 
 #[derive(Debug, Default, Clone)]
 pub(crate) struct Globals(HashMap<String, Expression>);
@@ -12,6 +12,10 @@ impl Globals {
         Self(HashMap::new())
     }
 
+    pub fn contains(&self, ident: &str) -> bool {
+        self.0.contains_key(ident)
+    }
+
     pub fn get(&self, ident: &str) -> Option<&Expression> {
         self.0.get(ident)
     }
@@ -232,9 +236,15 @@ impl Variables {
         var_id
     }
 
-    pub fn define_global(&mut self, ident: impl Into<String>, value: impl Into<Expression>) {
+    pub fn define_global(&mut self, ident: impl Into<String>, value: impl Into<Expression>) -> Result<(), ErrorKind> {
+        let ident = ident.into();
+        if self.globals.contains(&ident) {
+            return Err(ErrorKind::GlobalAlreadyAssigned(ident));
+        }
+
         let value = value.into();
-        self.globals.set(ident.into(), value)
+        self.globals.set(ident, value);
+        Ok(())
     }
 
     pub fn define_local(&mut self, ident: impl Into<String>, value: impl Into<Expression>) -> VarId {