[gjs/ewlsh/enumerable-interfaces] gi: Add enumeration hook for Interface prototypes

[Evan Welsh <ewlsh src gnome org>]

commit 1ce482efdfc62b8a3a3b5402108b0d25bcf799c6
Author: Evan Welsh <contact evanwelsh com>
Date:   Sun Jan 9 11:41:20 2022 -0800

    gi: Add enumeration hook for Interface prototypes
    
    This commit allows utilities in JavaScript to enumerate the methods
    available on a given interface.

 gi/interface.cpp | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 gi/interface.h   |  5 ++++
 2 files changed, 79 insertions(+), 1 deletion(-)
---
diff --git a/gi/interface.cpp b/gi/interface.cpp
index 925097e8..1bcc7a50 100644
--- a/gi/interface.cpp
+++ b/gi/interface.cpp
@@ -8,8 +8,12 @@
 #include <girepository.h>
 
 #include <js/Class.h>
+#include <js/Id.h>  // for JSID_VOID, PropertyKey, jsid
 #include <js/TypeDecls.h>
 #include <js/Utility.h>  // for UniqueChars
+#include <jsapi.h>       // for JS_ReportOutOfMemory
+
+#include <utility>  // for forward
 
 #include "gi/function.h"
 #include "gi/interface.h"
@@ -31,6 +35,75 @@ InterfacePrototype::~InterfacePrototype(void) {
     GJS_DEC_COUNTER(interface);
 }
 
+bool InterfacePrototype::new_enumerate_impl(
+    JSContext* cx, JS::HandleObject obj [[maybe_unused]],
+    JS::MutableHandleIdVector properties,
+    bool only_enumerable [[maybe_unused]]) {
+    unsigned n_interfaces;
+    GType* interfaces = g_type_interfaces(gtype(), &n_interfaces);
+
+    for (unsigned k = 0; k < n_interfaces; k++) {
+        GjsAutoInterfaceInfo iface_info =
+            g_irepository_find_by_gtype(nullptr, interfaces[k]);
+
+        if (!iface_info) {
+            continue;
+        }
+
+        int n_methods = g_interface_info_get_n_methods(iface_info);
+        int n_properties = g_interface_info_get_n_properties(iface_info);
+        if (!properties.reserve(properties.length() + n_methods +
+                                n_properties)) {
+            JS_ReportOutOfMemory(cx);
+            return false;
+        }
+
+        // Methods
+        for (int i = 0; i < n_methods; i++) {
+            GjsAutoFunctionInfo meth_info =
+                g_interface_info_get_method(iface_info, i);
+            GIFunctionInfoFlags flags = g_function_info_get_flags(meth_info);
+
+            if (flags & GI_FUNCTION_IS_METHOD) {
+                const char* name = meth_info.name();
+                jsid id = gjs_intern_string_to_id(cx, name);
+                if (id == JSID_VOID)
+                    return false;
+                properties.infallibleAppend(id);
+            }
+        }
+    }
+
+    g_free(interfaces);
+
+    if (info()) {
+        int n_methods = g_interface_info_get_n_methods(info());
+        int n_properties = g_interface_info_get_n_properties(info());
+        if (!properties.reserve(properties.length() + n_methods +
+                                n_properties)) {
+            JS_ReportOutOfMemory(cx);
+            return false;
+        }
+
+        // Methods
+        for (int i = 0; i < n_methods; i++) {
+            GjsAutoFunctionInfo meth_info =
+                g_interface_info_get_method(info(), i);
+            GIFunctionInfoFlags flags = g_function_info_get_flags(meth_info);
+
+            if (flags & GI_FUNCTION_IS_METHOD) {
+                const char* name = meth_info.name();
+                jsid id = gjs_intern_string_to_id(cx, name);
+                if (id == JSID_VOID)
+                    return false;
+                properties.infallibleAppend(id);
+            }
+        }
+    }
+
+    return true;
+}
+
 // See GIWrapperBase::resolve().
 bool InterfacePrototype::resolve_impl(JSContext* context, JS::HandleObject obj,
                                       JS::HandleId id, bool* resolved) {
@@ -111,7 +184,7 @@ const struct JSClassOps InterfaceBase::class_ops = {
     nullptr,  // addProperty
     nullptr,  // deleteProperty
     nullptr,  // enumerate
-    nullptr,  // newEnumerate
+    &InterfaceBase::new_enumerate,
     &InterfaceBase::resolve,
     nullptr,  // mayResolve
     &InterfaceBase::finalize,
diff --git a/gi/interface.h b/gi/interface.h
index 490b7093..9630b478 100644
--- a/gi/interface.h
+++ b/gi/interface.h
@@ -92,6 +92,11 @@ class InterfacePrototype
     bool resolve_impl(JSContext* cx, JS::HandleObject obj, JS::HandleId id,
                       bool* resolved);
 
+    GJS_JSAPI_RETURN_CONVENTION
+    bool new_enumerate_impl(JSContext* cx, JS::HandleObject obj,
+                            JS::MutableHandleIdVector properties,
+                            bool only_enumerable);
+
     // JS methods
 
     GJS_JSAPI_RETURN_CONVENTION