From 6a566b9cf5aa38f5f0d4e03c98c84e3a86961e9c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marc=20Andr=C3=A9=20Tanner?= <mat@brain-dump.org>
Date: Sun, 27 Nov 2016 21:09:44 +0100
Subject: sam: stricter command parsing

Properly detect unbalanced curly braces and spurious output at the
end of a group.
---
 sam.c      | 25 ++++++++++++++++++++-----
 sam.h      |  1 +
 vis-core.h |  1 +
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/sam.c b/sam.c
index 594de1c..7499242 100644
--- a/sam.c
+++ b/sam.c
@@ -404,6 +404,7 @@ const char *sam_error(enum SamError err) {
 		[SAM_ERR_SHELL]           = "Shell command expected",
 		[SAM_ERR_COMMAND]         = "Unknown command",
 		[SAM_ERR_EXECUTE]         = "Error executing command",
+		[SAM_ERR_NEWLINE]         = "Newline expected",
 	};
 
 	return err < LENGTH(error_msg) ? error_msg[err] : NULL;
@@ -695,7 +696,7 @@ static const CommandDef *command_lookup(Vis *vis, const char *name) {
 	return map_closest(vis->cmds, name);
 }
 
-static Command *command_parse(Vis *vis, const char **s, int level, enum SamError *err) {
+static Command *command_parse(Vis *vis, const char **s, enum SamError *err) {
 	if (!**s) {
 		*err = SAM_ERR_COMMAND;
 		return NULL;
@@ -727,17 +728,22 @@ static Command *command_parse(Vis *vis, const char **s, int level, enum SamError
 
 	if (strcmp(cmd->argv[0], "{") == 0) {
 		Command *prev = NULL, *next;
+		int level = vis->nesting_level++;
 		do {
 			while (**s == ' ' || **s == '\t' || **s == '\n')
 				(*s)++;
-			next = command_parse(vis, s, level+1, err);
+			next = command_parse(vis, s, err);
 			if (prev)
 				prev->next = next;
 			else
 				cmd->cmd = next;
 		} while ((prev = next));
+		if (level != vis->nesting_level) {
+			*err = SAM_ERR_UNMATCHED_BRACE;
+			goto fail;
+		}
 	} else if (strcmp(cmd->argv[0], "}") == 0) {
-		if (level == 0) {
+		if (vis->nesting_level-- == 0) {
 			*err = SAM_ERR_UNMATCHED_BRACE;
 			goto fail;
 		}
@@ -791,7 +797,7 @@ static Command *command_parse(Vis *vis, const char **s, int level, enum SamError
 				goto fail;
 			cmd->cmd->cmddef = command_lookup(vis, cmddef->defcmd);
 		} else {
-			if (!(cmd->cmd = command_parse(vis, s, level, err)))
+			if (!(cmd->cmd = command_parse(vis, s, err)))
 				goto fail;
 			if (strcmp(cmd->argv[0], "X") == 0 || strcmp(cmd->argv[0], "Y") == 0) {
 				Command *sel = command_new("s");
@@ -811,10 +817,19 @@ fail:
 }
 
 static Command *sam_parse(Vis *vis, const char *cmd, enum SamError *err) {
+	vis->nesting_level = 0;
 	const char **s = &cmd;
-	Command *c = command_parse(vis, s, 0, err);
+	Command *c = command_parse(vis, s, err);
 	if (!c)
 		return NULL;
+	while (**s == ' ' || **s == '\t' || **s == '\n')
+		(*s)++;
+	if (**s) {
+		*err = SAM_ERR_NEWLINE;
+		command_free(c);
+		return NULL;
+	}
+
 	Command *sel = command_new("s");
 	if (!sel) {
 		command_free(c);
diff --git a/sam.h b/sam.h
index de7e910..7d063f4 100644
--- a/sam.h
+++ b/sam.h
@@ -14,6 +14,7 @@ enum SamError {
 	SAM_ERR_SHELL,
 	SAM_ERR_COMMAND,
 	SAM_ERR_EXECUTE,
+	SAM_ERR_NEWLINE,
 };
 
 bool sam_init(Vis*);
diff --git a/vis-core.h b/vis-core.h
index 79270f6..842c753 100644
--- a/vis-core.h
+++ b/vis-core.h
@@ -174,6 +174,7 @@ struct Vis {
 	Mode *mode;                          /* currently active mode, used to search for keybindings */
 	Mode *mode_prev;                     /* previsouly active user mode */
 	bool initialized;                    /* whether UI and Lua integration has been initialized */
+	int nesting_level;                   /* parsing state to hold keep track of { } nesting level */
 	volatile bool running;               /* exit main loop once this becomes false */
 	int exit_status;                     /* exit status when terminating main loop */
 	volatile sig_atomic_t cancel_filter; /* abort external command/filter (SIGINT occured) */
-- 
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