From d4878d9a45e50351670337d14506a68db8134fe4 Mon Sep 17 00:00:00 2001
From: Oldes <oldes.huhuman@gmail.com>
Date: Wed, 6 Sep 2023 11:47:19 +0200
Subject: [PATCH] FEAT: allow custom `mold` callback for context handles to
 provide additional handle's info, if wanted

---
 src/core/s-mold.c       | 12 ++++++++++++
 src/include/sys-value.h |  3 ++-
 src/os/host-ext-test.c  | 16 ++++++++++++++++
 3 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/src/core/s-mold.c b/src/core/s-mold.c
index 4b15879a93..8bd1839126 100644
--- a/src/core/s-mold.c
+++ b/src/core/s-mold.c
@@ -558,6 +558,18 @@ STOID Mold_Handle(REBVAL *value, REB_MOLD *mold)
 		if (IS_CONTEXT_HANDLE(value)) {
 			if (!IS_USED_HOB(VAL_HANDLE_CTX(value)))
 				Append_Bytes(mold->series, " unset!");
+			else {
+				REBCNT idx = VAL_HANDLE_CTX(value)->index;
+				REBHSP spec = PG_Handles[idx];
+				REBINT len;
+				if (spec.mold) {
+					len = spec.mold(VAL_HANDLE_CTX(value), BUF_PRINT);
+					if (len > 0) {
+						Append_Byte(mold->series, ' ');
+						Append_Bytes_Len(mold->series, STR_HEAD(BUF_PRINT), len);
+					}
+				}
+			}
 		}
 		Append_Byte(mold->series, ']');
 	}
diff --git a/src/include/sys-value.h b/src/include/sys-value.h
index f955f898ff..95d45a8f2a 100644
--- a/src/include/sys-value.h
+++ b/src/include/sys-value.h
@@ -997,8 +997,8 @@ typedef void (*REBDOF)(REBVAL *ds);				// DO evaltype dispatch function
 typedef int  (*REBPAF)(REBVAL *ds, REBVAL *p, REBCNT a); // Port action func
 
 typedef int     (*REB_HANDLE_FREE_FUNC)(void *hnd);
+typedef int     (*REB_HANDLE_MOLD_FUNC)(void *hnd, REBSER *ser);
 typedef int     (*REB_HANDLE_EVAL_PATH)(REBHOB *hob, REBCNT word, REBCNT *type, RXIARG *arg);
-typedef REBSER* (*REB_HANDLE_MOLD_FUNC)(REBSER *mold, void *hnd); //TODO: not used yet!
 
 typedef void (*ANYFUNC)(void *);
 typedef void (*TRYFUNC)(void *);
@@ -1101,6 +1101,7 @@ typedef struct Reb_Handle_Spec {
 	REB_HANDLE_FREE_FUNC free;
 	REB_HANDLE_EVAL_PATH get_path;
 	REB_HANDLE_EVAL_PATH set_path;
+	REB_HANDLE_MOLD_FUNC mold;
 } REBHSP;
 
 typedef struct Reb_Handle_Context {
diff --git a/src/os/host-ext-test.c b/src/os/host-ext-test.c
index 520f96e2bc..7992e9c995 100644
--- a/src/os/host-ext-test.c
+++ b/src/os/host-ext-test.c
@@ -499,6 +499,21 @@ int XTestContext_set_path(REBHOB *hob, REBCNT word, REBCNT *type, RXIARG *arg) {
 	return PE_OK;
 }
 
+int XTestContext_mold(REBHOB *hob, REBSER *str) {
+	int len;
+	XTEST* xtest = (XTEST*)hob->data;
+
+	if (!str || !xtest) return 0;
+
+	len = snprintf(
+		SERIES_DATA(str),
+		SERIES_REST(str),
+		"0#%lx id: %u", (unsigned long)hob->data, xtest->id
+	);
+	if (len > 0) SERIES_TAIL(str) += len;
+	return len;
+}
+
 
 
 void Init_Ext_Test(void)
@@ -510,6 +525,7 @@ void Init_Ext_Test(void)
 	spec.free      = XTestContext_release;
 	spec.get_path  = XTestContext_get_path;
 	spec.set_path  = XTestContext_set_path;
+	spec.mold      = XTestContext_mold;
 	Handle_XTest = RL_REGISTER_HANDLE_SPEC("XTEST", &spec);
 }
 #endif //TEST_EXTENSIONS
\ No newline at end of file