Berry improved `super()` for inheritance

lib/libesp32/Berry/src/be_baselib.c

@@ -11,6 +11,9 @@
 #include "be_mem.h"
 #include "be_gc.h"
 #include "be_class.h"
+#include "be_vector.h"
+#include "be_string.h"
+#include "be_map.h"
 #include <string.h>
 
 #define READLINE_STEP       100
@@ -73,18 +76,89 @@ static int l_input(bvm *vm)
     return m_readline(vm);
 }
 
+/* Look in the current class and all super classes for a method corresponding to a specific closure pointer */
+static bclass *find_class_closure(bclass *cl, bclosure *needle)
+{
+    while (cl) {
+        bmapnode *node;  /* iterate on members of the class */
+        bmap *members = be_class_members(cl);
+        if (members) {  /* only iterate if there are members */
+            bmapiter iter = be_map_iter();
+            while ((node = be_map_next(members, &iter)) != NULL) {
+                if (var_type(&node->value) == BE_CLOSURE) {  /* only native functions are considered */
+                    bclosure *clos_iter = var_toobj(&node->value);  /* retrieve the method's closure */
+                    if (clos_iter == needle) {
+                        /* we found the closure, we now know its class */
+                        return cl;
+                    }
+                }
+            }
+        }
+        cl = be_class_super(cl);  /* move to super class */
+    }
+    return NULL;  /* not found */
+}
+
 static int l_super(bvm *vm)
 {
     int argc = be_top(vm);
-    if (argc) {
-        if (argc >= 2) {
-            if (be_isinstance(vm, 1) && be_isclass(vm, 2)) {
-                /* leveled super, i.e. fix the parenthood class level */
+
+    /* if no argument, or arg 1 is nil, return nil */
+    if (argc == 0 || be_isnil(vm, 1)) {
+        be_return_nil(vm);
+    }
+
+    /* if arg 1 is a class, simply return super */
+    if (be_isclass(vm, 1)) {
+        be_getsuper(vm, 1);
+        be_return(vm);
+    }
+
+    /* arg 1 is an instance */
+    if (be_isinstance(vm, 1)) {
         binstance *o = var_toobj(be_indexof(vm, 1));
-                bclass *bc = var_toobj(be_indexof(vm, 2));
+        bclass *target_class = NULL;  /* the minimal class expected, or any super class */
+        bclass *base_class = NULL;  /* current class of the caller, if any */
+
+        /* if arg 2 is present, it must be a class */
+        if (argc >= 2) {
+            if (be_isclass(vm, 2)) {
+                target_class = var_toobj(be_indexof(vm, 2));
+            } else if (be_isnil(vm, 2)) {
+                // ignore, revert to standard super() behavior if second arg is explicit nil
+            } else {
+                be_raise(vm, "type_error", "leveled super() requires 'instance' and 'class' arguments");
+            }
+        }
+
+        /* now the more complex part, if arg 1 is an instance */
+        /* if instance is the sole argument, try to find if it comes from a method of a class and set 'base_class' accordinly */
+        /* later it will be equivalent to passing this class as second argument */
+        if (argc == 1) {
+            /* we look in the callstack for the caller's closure */
+            int size = be_stack_count(&vm->callstack);
+            if (size >= 2) {  /* need at least 2 stackframes: current (for super() native) and caller (the one we are interested in) */
+                bcallframe *caller = be_vector_at(&vm->callstack, size - 2);  /* get the callframe of caller */
+                bvalue *func = caller->func;  /* function object of caller */
+                if (var_type(func) == BE_CLOSURE) {  /* only useful if the caller is a Berry closure (i.e. not native) */
+                    bclosure *clos_ctx = var_toobj(func);  /* this is the closure we look for in the class chain */
+                    base_class = find_class_closure(o->_class, clos_ctx);  /* iterate on current and super classes to find where the closure belongs */
+                }
+            }
+        }
+
+        if (base_class || target_class) {
+            if (base_class) {
+                target_class = base_class->super;
+                if (!target_class) be_return_nil(vm);   /* fast exit if top class */
+            }
+            /* leveled super, i.e. fix the parenthood class level */
+            if (o) {
+                o = be_instance_super(o);   /* always skip the current class and move to super */
+            }
             while (o) {
                 bclass *c = be_instance_class(o);
-                    if (c == bc) break;         /* found */
+                if (c == target_class) break;         /* found */
                 o = be_instance_super(o);
             }
             bvalue *top = be_incrtop(vm);
@@ -95,14 +169,12 @@ static int l_super(bvm *vm)
             }
             be_return(vm);
         } else {
-                be_raise(vm, "type_error", "leveled super() requires 'instance' and 'class' arguments");
-            }
-        } else {
-            /* simple use of super */
             be_getsuper(vm, 1);
             be_return(vm);
         }
     }
+
+    /* fall through, return nil if we don't know what to do */
     be_return_nil(vm);
 }
 

lib/libesp32/Berry/src/be_class.c

@@ -14,6 +14,7 @@
 #include "be_vm.h"
 #include "be_func.h"
 #include "be_var.h"
+#include <string.h>
 
 #define check_members(vm, c)            \
     if (!(c)->members) {                \
@@ -237,6 +238,11 @@ bbool be_class_newobj(bvm *vm, bclass *c, bvalue *reg, int argc, int mode)
     return bfalse;
 }
 
+/* Default empty constructor */
+static int default_init_native_method(bvm *vm) {
+    be_return_nil(vm);
+}
+
 /* Find instance member by name and copy value to `dst` */
 /* Input: none of `obj`, `name` and `dst` may not be NULL */
 /* Returns the type of the member or BE_NONE if member not found */
@@ -253,6 +259,11 @@ int be_instance_member(bvm *vm, binstance *instance, bstring *name, bvalue *dst)
     if (obj) {
         return type;
     } else {  /* if no method found, try virtual */
+        /* if 'init' does not exist, create a virtual empty constructor */
+        if (strcmp(str(name), "init") == 0) {
+            var_setntvfunc(dst, default_init_native_method);
+            return var_type(dst);
+        } else {
             /* get method 'member' */
             obj = instance_member(vm, instance, str_literal(vm, "member"), vm->top);
             if (obj && basetype(var_type(vm->top)) == BE_FUNCTION) {
@@ -272,6 +283,7 @@ int be_instance_member(bvm *vm, binstance *instance, bstring *name, bvalue *dst)
                 }
             }
         }
+    }
     return BE_NONE;
 }
 

lib/libesp32/Berry/tests/super_auto.be

@@ -0,0 +1,132 @@
+#- test for new auto class inference of super() -#
+
+#- test that we can call init() even if it's not defined -#
+class Z end
+z=Z()
+assert(z.init != nil)
+z.init()  #- should do nothing -#
+
+#- check the old way still works -#
+class A1
+    var a
+    def init(a)
+        self.a = a
+    end
+end
+class B1:A1
+    var b
+    def init(a,b)
+        super(self,A1).init(a)
+        self.b = b
+    end
+end
+class C1:B1
+    var c
+    def init(a,b,c)
+        super(self,B1).init(a,b)
+        self.c = c
+    end
+end
+#- -#
+c1=C1(1,2,3)
+assert(c1.a == 1)
+assert(c1.b == 2)
+assert(c1.c == 3)
+
+#- test simple behavior -#
+class A0 var a end
+class B0:A0 var b end
+class C0:B0 end
+c0=C0()
+assert(classof(c0) == C0)
+assert(classof(super(c0)) == B0)
+assert(classof(super(super(c0))) == A0)
+assert(super(super(super(c0))) == nil)
+
+assert(super(C0) == B0)
+assert(super(super(C0)) == A0)
+assert(super(super(super(C0))) == nil)
+
+assert(classof(super(c0,B0)) == B0)
+assert(classof(super(c0,A0)) == A0)
+
+#- test auto inference of target superclass -#
+class A
+    var a
+    def init(a)
+        self.a = a
+    end
+end
+class B:A
+    var b
+    def init(a,b)
+        super(self).init(a)
+        self.b = b
+    end
+end
+class C:B
+    var c
+    def init(a,b,c)
+        super(self).init(a,b)
+        self.c = c
+    end
+end
+#- -#
+c=C(1,2,3)
+
+assert(c.a == 1)
+assert(c.b == 2)
+assert(c.c == 3)class A
+end
+class B:A
+    var b
+    def init(a,b) super(self).init(a) self.b = b end
+end
+class C:B
+    var c
+    def init(a,b,c) super(self).init(a,b) self.c = c end
+end
+c=C(1,2,3)
+
+#- variant if A2 does not have an init() method, still works -#
+class A2
+    static a=1
+end
+class B2:A2
+    var b
+    def init(a,b) super(self).init(a) self.b = b end
+end
+class C2:B2
+    var c
+    def init(a,b,c) super(self).init(a,b) self.c = c end
+end
+#- -#
+c2=C2(1,2,3)
+assert(c2.a == 1)
+assert(c2.b == 2)
+assert(c2.c == 3)
+
+#- difference in behavior whether the second arg is provided or not -#
+class A3
+end
+class B3:A3
+    def b1()
+        return super(self)
+    end
+    def b2(c)
+        return super(self, c)
+    end
+end
+class C3:B3
+end
+#- -#
+b3=B3()
+c3=C3()
+assert(classof(c3.b1()) == A3)
+assert(classof(b3.b1()) == A3)
+assert(classof(c3.b2(B3)) == B3)
+assert(classof(c3.b2(A3)) == A3)
+
+assert(classof(c3.b2(nil)) == B3)  #- testing super(self<C3>,nil) in B3::b2() -#
+
+assert(c3.b2(C3) == nil)  #- if specifying the current class, can't find any relevant class in supers -#

lib/libesp32/Berry/tests/super_leveled.be

@@ -26,10 +26,9 @@ assert(classname(super(super(C))) == 'A')
 assert(super(super(super(C))) == nil)
 
 #- super() levele -#
-assert(super(a,A) == a)
-assert(classname(super(a,A)) == 'A')
-assert(classname(super(b,B)) == 'B')
-assert(classname(super(c,C)) == 'C')
+assert(super(a,A) == nil)
+assert(super(b,B) == nil)
+assert(super(c,C) == nil)
 assert(classname(super(c,B)) == 'B')
 assert(classname(super(c,A)) == 'A')
 assert(super(c,map) == nil) #- not a parent class -#