From b7aa73406651f775ef8ccfc66a2697569927f4bc Mon Sep 17 00:00:00 2001
From: Dane Jensen <dhcjensen@gmail.com>
Date: Sat, 15 Aug 2026 10:50:48 -0700
Subject: [PATCH] Added read-only helper functions to the json api which handle
 errors.

---
 json.c          | 134 ++++++++++++++++++++++++++++++++++++++++++++++--
 layout-custom.c | 108 +++++++++++++++++---------------------
 tmux.h          |  14 ++++-
 3 files changed, 191 insertions(+), 65 deletions(-)

diff --git a/json.c b/json.c
index 768b8beae..57f1b9068 100644
--- a/json.c
+++ b/json.c
@@ -26,7 +26,8 @@
 
 #include "tmux.h"
 
-#define TOKENS_MAX	4096
+#define INPUT_MAX	8192
+#define TOKENS_MAX	(INPUT_MAX)
 #define ERROR_CTX_LEN	8
 
 /* JSON Token types. */
@@ -115,6 +116,7 @@ static struct json_node	*json_parse_boolean(struct json_token **, const char *,
 static int		 json_node_cmp(struct json_node *, struct json_node *);
 RB_GENERATE_STATIC(json_fields, json_node, oentry, json_node_cmp);
 
+/* Comparator for the json_fields tree. */
 static int
 json_node_cmp(struct json_node *a, struct json_node *b)
 {
@@ -133,6 +135,7 @@ json_parse(const char *input, char **cause)
 	return (json_parse_tokens(&tokens, cause));
 }
 
+/* Returns a field node from an object node. */
 struct json_node *
 json_find(struct json_node *jn, const char *key)
 {
@@ -145,8 +148,9 @@ json_find(struct json_node *jn, const char *key)
 	return (RB_FIND(json_fields, &jn->fields, &tmp));
 }
 
+/* Returns the first member of an array node. */
 struct json_node *
-json_array_first(struct json_node *jn)
+json_array_first(const struct json_node *jn)
 {
 	if (jn->type != NODE_ARRAY)
 		return (NULL);
@@ -154,8 +158,9 @@ json_array_first(struct json_node *jn)
 	return (TAILQ_FIRST(&jn->members));
 }
 
+/* Returns the next member of an array's member node. */
 struct json_node *
-json_array_next(struct json_node *jn)
+json_array_next(const struct json_node *jn)
 {
 	if (jn->parent->type != NODE_ARRAY)
 		return (NULL);
@@ -163,6 +168,7 @@ json_array_next(struct json_node *jn)
 	return (TAILQ_NEXT(jn, aentry));
 }
 
+/* Returns the string value from a node. */
 int
 json_get_string(struct json_node *jn, const char **s)
 {
@@ -173,6 +179,7 @@ json_get_string(struct json_node *jn, const char **s)
 	return (0);
 }
 
+/* Returns the number value from a node. */
 int
 json_get_number(struct json_node *jn, int64_t *i)
 {
@@ -183,6 +190,7 @@ json_get_number(struct json_node *jn, int64_t *i)
 	return (0);
 }
 
+/* Returns the boolean value from a node. */
 int
 json_get_boolean(struct json_node *jn, int *b)
 {
@@ -193,6 +201,7 @@ json_get_boolean(struct json_node *jn, int *b)
 	return (0);
 }
 
+/* Returns the object value from a node. */
 int
 json_get_object(struct json_node *jn, struct json_node **o)
 {
@@ -202,6 +211,8 @@ json_get_object(struct json_node *jn, struct json_node **o)
 	*o = jn;
 	return (0);
 }
+
+/* Returns the array value from a node. */
 int
 json_get_array(struct json_node *jn, struct json_node **a)
 {
@@ -212,6 +223,123 @@ json_get_array(struct json_node *jn, struct json_node **a)
 	return (0);
 }
 
+/* Returns the string value from a given key in an object node. */
+const char *
+json_find_string(const struct json_node *jn, const char *key, char **cause)
+{
+	struct json_node	*field;
+	static char		 ret[INPUT_MAX];
+
+	if ((field = json_find((struct json_node *)jn, key)) == NULL) {
+		if (cause != NULL)
+			xasprintf(cause, "key \"%s\" not found", key);
+		return (NULL);
+	}
+	
+	if (field->type != NODE_STRING) {
+		if (cause != NULL)
+			xasprintf(cause, "key \"%s\" expected STRING value",
+			    key);
+		return (NULL);
+	}
+
+	if (xsnprintf(ret, sizeof ret, "%s", field->str) >= (int)sizeof ret) {
+		if (cause != NULL)
+			xasprintf(cause, "string overflow for key \"%s\"", key);
+		return (NULL);
+	}
+
+	return (ret);
+}
+
+/* Returns the number value from a given key in an object node. */
+const int64_t *
+json_find_number(const struct json_node *jn, const char *key, char **cause)
+{
+	struct json_node	*field;
+	static int64_t		 ret;
+
+	if ((field = json_find((struct json_node *)jn, key)) == NULL) {
+		if (cause != NULL)
+			xasprintf(cause, "key \"%s\" not found", key);
+		return (NULL);
+	}
+	if (field->type != NODE_NUMBER) {
+		if (cause != NULL)
+			xasprintf(cause, "key \"%s\" expected NUMBER value",
+			    key);
+		return (NULL);
+	}
+	ret = field->num;
+
+	return (&ret);
+}
+
+/* Returns the boolean value from a given key in an object node. */
+const int *
+json_find_boolean(const struct json_node *jn, const char *key, char **cause)
+{
+	struct json_node	*field;
+	static int		 ret;
+
+	if ((field = json_find((struct json_node *)jn, key)) == NULL) {
+		if (cause != NULL)
+			xasprintf(cause, "key \"%s\" not found", key);
+		return (NULL);
+	}
+	if (field->type != NODE_BOOLEAN) {
+		if (cause != NULL)
+			xasprintf(cause, "key \"%s\" expected BOOLEAN value",
+			    key);
+		return (NULL);
+	}
+	ret = field->boolean;
+
+	return (&ret);
+}
+
+/* Returns the object value from a given key in an object node. */
+const struct json_node *
+json_find_object(const struct json_node *jn, const char *key, char **cause)
+{
+	struct json_node	*field;
+
+	if ((field = json_find((struct json_node *)jn, key)) == NULL) {
+		if (cause != NULL)
+			xasprintf(cause, "key \"%s\" not found", key);
+		return (NULL);
+	}
+	if (field->type != NODE_OBJECT) {
+		if (cause != NULL)
+			xasprintf(cause, "key \"%s\" expected OBJECT value",
+			    key);
+		return (NULL);
+	}
+
+	return (field);
+}
+
+/* Returns the array value from a given key in an object node. */
+const struct json_node *
+json_find_array(const struct json_node *jn, const char *key, char **cause)
+{
+	struct json_node	*field;
+
+	if ((field = json_find((struct json_node *)jn, key)) == NULL) {
+		if (cause != NULL)
+			xasprintf(cause, "key \"%s\" not found", key);
+		return (NULL);
+	}
+	if (field->type != NODE_ARRAY) {
+		if (cause != NULL)
+			xasprintf(cause, "key \"%s\" expected ARRAY value",
+			    key);
+		return (NULL);
+	}
+
+	return (field);
+}
+
 /* Fill an error cause. */
 static void
 json_error(char **cause, const char *reason, const char *input)
diff --git a/layout-custom.c b/layout-custom.c
index 84c7079b0..a021a8df0 100644
--- a/layout-custom.c
+++ b/layout-custom.c
@@ -89,7 +89,8 @@ static void			 layout_assign(struct window *,
 				     struct layout_parse_ctx *);                                  
 static void			 layout_parse_apply_ctx(struct window *,
 				     struct layout_parse_ctx *);
-static struct layout_cell	*layout_parse_json_layout(struct json_node *,
+static struct layout_cell	*layout_parse_json_layout(
+				     const struct json_node *,
 				     struct layout_cell *,
 				     struct layout_parse_ctx *);
 
@@ -702,27 +703,22 @@ fail:
 static int
 layout_parse_json(struct json_node *jnroot, struct layout_parse_ctx *pctx)
 {
-	struct json_node	 *jn, *field, *object;
+	struct json_node	 *jn;
+	const struct json_node	 *object;
+	const int64_t		 *num;
 	char			**cause = pctx->cause;
 
 	if (json_get_object(jnroot, &jn) != 0) {
-		*cause = xstrdup("invalid json");
+		*cause = xstrdup("invalid layout json");
 		goto fail;
 	}
-	if ((field = json_find(jn, "V")) == NULL) {
-		*cause = xstrdup("missing version");
+
+	if ((num = json_find_number(jn, "V", cause)) == NULL) {
 		goto fail;
 	}
-	if (json_get_number(field, &pctx->version) != 0) {
-		*cause = xstrdup("invalid version type");
-		goto fail;
-	}
-	if ((field = json_find(jn, "L")) == NULL) {
-		*cause = xstrdup("missing layout");
-		goto fail;
-	}
-	if (json_get_object(field, &object) != 0) {
-		*cause = xstrdup("invalid version type");
+	pctx->version = *num;
+
+	if ((object = json_find_object(jn, "L", cause)) == NULL) {
 		goto fail;
 	}
 	pctx->root = layout_parse_json_layout(object, NULL, pctx);
@@ -743,20 +739,19 @@ fail:
 
 /* Parse nodes into layout cells. */
 static struct layout_cell *
-layout_parse_json_layout(struct json_node *node, struct layout_cell *lcparent,
-    struct layout_parse_ctx *pctx)
+layout_parse_json_layout(const struct json_node *node,
+    struct layout_cell *lcparent, struct layout_parse_ctx *pctx)
 {
-	struct json_node	*field, *array, *member;
+	struct json_node	*member;
 	struct layout_cell	*lc = layout_create_cell(lcparent), *lcchild;
+	const struct json_node	*array;
 	const char		*str;
-	char			*endptr;
-	int64_t			 num;
+	const int64_t		*num;
+	const int		*boolean;
+	char			*endptr, **cause = pctx->cause;
 	u_int			 id, index, zindex, active = -1, last = -1;
-	int			 boolean;
 
-	if ((field = json_find(node, "t")) == NULL)
-		goto fail;
-	if (json_get_string(field, &str) != 0)
+	if ((str = json_find_string(node, "t", cause)) == NULL)
 		goto fail;
 	if (strcmp(str, "p") == 0)
 		lc->type = LAYOUT_WINDOWPANE;
@@ -767,63 +762,56 @@ layout_parse_json_layout(struct json_node *node, struct layout_cell *lcparent,
 	else
 		goto fail;
 
-	if ((field = json_find(node, "w")) == NULL)
+	if ((num = json_find_number(node, "w", cause)) == NULL)
 		goto fail;
-	if (json_get_number(field, &num) != 0)
-		goto fail;
-	lc->g.sx = num;
+	lc->g.sx = *num;
 
-	if ((field = json_find(node, "h")) == NULL)
+	if ((num = json_find_number(node, "h", cause)) == NULL)
 		goto fail;
-	if (json_get_number(field, &num) != 0)
-		goto fail;
-	lc->g.sy = num;
+	lc->g.sy = *num;
 
-	if ((field = json_find(node, "x")) == NULL)
+	if ((num = json_find_number(node, "x", cause)) == NULL)
 		goto fail;
-	if (json_get_number(field, &num) != 0)
-		goto fail;
-	lc->g.xoff = num;
+	lc->g.xoff = *num;
 
-	if ((field = json_find(node, "y")) == NULL)
+	if ((num = json_find_number(node, "y", cause)) == NULL)
 		goto fail;
-	if (json_get_number(field, &num) != 0)
-		goto fail;
-	lc->g.yoff = num;
+	lc->g.yoff = *num;
 
 	if (lc->type == LAYOUT_WINDOWPANE) {
-		if ((field = json_find(node, "I")) == NULL)
-			goto fail;
-		if (json_get_string(field, &str) != 0)
+		if ((str = json_find_string(node, "I", cause)) == NULL)
 			goto fail;
 		errno = 0;
 		if (*str != '%') {
+			*cause = xstrdup("pane id must begin with '%'");
 			goto fail;
 		}
 		id = strtol(str + 1, &endptr, 10);
 		if (errno != 0 || endptr != str + strlen(str)) {
+			*cause = xstrdup("invalid number string '%s'");
 			goto fail;
 		}
-		if ((field = json_find(node, "i")) == NULL)
+		if ((num = json_find_number(node, "i", cause)) == NULL)
 			goto fail;
-		if (json_get_number(field, &num) != 0)
-			goto fail;
-		index = num;
+		index = *num;
 
-		if ((field = json_find(node, "a")) != NULL) {
-			if (json_get_boolean(field, &boolean) != 0)
+		if (json_find((struct json_node *)node, "a") != NULL) {
+			boolean = json_find_boolean(node, "a", cause);
+			if (boolean == NULL)
 				goto fail;
-			active = boolean;
-		} else if ((field = json_find(node, "l")) != NULL) {
-			if (json_get_number(field, &num) != 0)
+			active = *boolean;
+		} else if (json_find((struct json_node *)node, "l") != NULL) {
+			num = json_find_number(node, "l", cause);
+			if (num == NULL)
 				goto fail;
-			last = num;
+			last = *num;
 		}
 
-		if ((field = json_find(node, "z")) != NULL) {
-			if (json_get_number(field, &num) != 0)
+		if (json_find((struct json_node *)node, "z") != NULL) {
+			num = json_find_number(node, "z", cause);
+			if (num == NULL)
 				goto fail;
-			zindex = num;
+			zindex = *num;
 			lc->flags |= LAYOUT_CELL_FLOATING;
 		} else
 			zindex = INT_MAX;
@@ -831,12 +819,12 @@ layout_parse_json_layout(struct json_node *node, struct layout_cell *lcparent,
 		layout_parse_add_cctx(pctx, lc, active, last, id, index,
 		    zindex);
 	} else {
-		if ((field = json_find(node, "c")) == NULL)
+		if ((array = json_find_array(node, "c", cause)) == NULL)
 			goto fail;
-		if (json_get_array(field, &array) != 0)
-			goto fail;
-		if ((member = json_array_first(array)) == NULL)
+		if ((member = json_array_first(array)) == NULL) {
+			*cause = xstrdup("nodes must have children");
 			goto fail;
+		}
 		while (member != NULL) {
 			lcchild = layout_parse_json_layout(member, lc,
 				pctx);
diff --git a/tmux.h b/tmux.h
index d9e93e5fe..448bef335 100644
--- a/tmux.h
+++ b/tmux.h
@@ -4278,8 +4278,8 @@ void			 hyperlinks_free(struct hyperlinks *);
 struct json_node	*json_parse(const char *, char **);
 void			 json_destroy_node(struct json_node *);
 struct json_node	*json_find(struct json_node *, const char *);
-struct json_node	*json_array_first(struct json_node *);
-struct json_node	*json_array_next(struct json_node *);
+struct json_node	*json_array_first(const struct json_node *);
+struct json_node	*json_array_next(const struct json_node *);
 int			 json_get_string(struct json_node *, const char **);
 int			 json_get_number(struct json_node *, int64_t *);
 int			 json_get_boolean(struct json_node *, int *);
@@ -4287,5 +4287,15 @@ int			 json_get_object(struct json_node *,
 			     struct json_node **);
 int			 json_get_array(struct json_node *,
 			     struct json_node **);
+const char		*json_find_string(const struct json_node *,
+			     const char *, char **);
+const int64_t		*json_find_number(const struct json_node *,
+			     const char *, char **);
+const int		*json_find_boolean(const struct json_node *,
+			     const char *, char **);
+const struct json_node	*json_find_object(const struct json_node *,
+			     const char *, char **);
+const struct json_node	*json_find_array(const struct json_node *,
+			     const char *, char **);
 
 #endif /* TMUX_H */