Split Context.lookup into lookup and lookupMut

src/main.zig

@@ -42,13 +42,21 @@ pub fn Context(comptime ctx: anytype) type {
         pub const Pair = @import("./pair.zig").Pair(ctx);
         pub const World = @import("./world.zig").World(ctx);
 
-        /// Returns a pointer unique to this context and the provided type
+        /// Looks up an entity ID unique to this `Context` for the provided
+        /// type that has been registered previously, typically done by
+        /// calling functions such as `World.component(...)`.
+        pub fn lookup(comptime T: type) c.ecs_entity_t {
+            return lookupMut(T).*;
+        }
+
+        /// Returns a pointer unique to this `Context` and the provided type
         /// that holds an entity ID. Useful for associating types to entities.
-        pub fn lookup(comptime T: type) *c.ecs_entity_t {
+        pub fn lookupMut(comptime T: type) *c.ecs_entity_t {
             _ = T; // Only necessary to create a unique type.
-            return &(struct {
+            const EntityHolder = struct {
                 pub var id: c.ecs_entity_t = 0;
-            }).id;
+            };
+            return &EntityHolder.id;
         }
 
         /// Converts the specified value to an `ecs_entity_t`.
@@ -67,7 +75,7 @@ pub fn Context(comptime ctx: anytype) type {
                 c.ecs_entity_t => value,
                 Entity => value.raw,
                 ?Entity => if (value) |v| v.raw else 0,
-                type => lookup(value).*,
+                type => lookup(value),
                 else => @compileError("Value of type " ++ @typeName(@TypeOf(value)) ++ " can't be converted to Entity"),
             };
         }
@@ -105,7 +113,7 @@ pub fn Context(comptime ctx: anytype) type {
                 // c.ecs_entity_t => value,
                 Entity => value.raw,
                 ?Entity => if (value) |v| v.raw else 0,
-                type => lookup(value).*,
+                type => lookup(value),
                 else => @compileError("Value of type " ++ @typeName(T) ++ " can't be converted to Id"),
             };
         }

src/test/flecs/world.zig

@@ -56,8 +56,8 @@ test "World_progress_w_0" {
     try expect.equal(null, ctx.param);
 
     try expect.equal(e1.raw, ctx.e[0]);
-    try expect.equal(Context.lookup(Position).*, ctx.c[0][0]);
-    try expect.equal(Context.lookup(Velocity).*, ctx.c[0][1]);
+    try expect.equal(Context.lookup(Position), ctx.c[0][0]);
+    try expect.equal(Context.lookup(Velocity), ctx.c[0][1]);
     try expect.equal(0, ctx.s[0][0]);
     try expect.equal(0, ctx.s[0][1]);
 
@@ -93,8 +93,8 @@ test "World_progress_w_t" {
     try expect.equal(null, ctx.param);
 
     try expect.equal(e1.raw, ctx.e[0]);
-    try expect.equal(Context.lookup(Position).*, ctx.c[0][0]);
-    try expect.equal(Context.lookup(Velocity).*, ctx.c[0][1]);
+    try expect.equal(Context.lookup(Position), ctx.c[0][0]);
+    try expect.equal(Context.lookup(Velocity), ctx.c[0][1]);
     try expect.equal(0, ctx.s[0][0]);
     try expect.equal(0, ctx.s[0][1]);
 

src/world.zig

@@ -98,7 +98,7 @@ pub fn World(comptime ctx: anytype) type {
             if (@sizeOf(T) > 0) @compileError("'" ++ @typeName(T) ++ "' must be a zero-sized type");
             const name = meta.simpleTypeName(T);
             const result = try self.entity(.{ .name = name, .symbol = name }, .{});
-            Context.lookup(T).* = result.raw;
+            Context.lookupMut(T).* = result.raw;
             return result;
         }
 
@@ -114,7 +114,7 @@ pub fn World(comptime ctx: anytype) type {
 
             const result = c.ecs_component_init(self.raw, &desc);
             if (result == 0) return flecs.getLastErrorOrUnknown();
-            Context.lookup(T).* = result;
+            Context.lookupMut(T).* = result;
             return Entity.fromRaw(self, result);
         }