From 9643ed6d270c607a292b133adf62871058fec1a5 Mon Sep 17 00:00:00 2001
From: Jakub Rzeszutko <jakub.rzeszutko@nordicsemi.no>
Date: Thu, 29 Nov 2018 09:08:20 +0100
Subject: [PATCH] shell: fix double new line print for RTT backend

In case terminal sends `\r\n` on the Enter button
shell will go to the new line twice and it will print
prompt twice. This patch fixes it.

Signed-off-by: Jakub Rzeszutko <jakub.rzeszutko@nordicsemi.no>
---
 include/shell/shell.h |  1 +
 subsys/shell/shell.c  | 36 ++++++++++++++++++++++++++++--------
 2 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/include/shell/shell.h b/include/shell/shell.h
index 8ca31d80c0b..57f6d5f3e8a 100644
--- a/include/shell/shell.h
+++ b/include/shell/shell.h
@@ -349,6 +349,7 @@ struct shell_flags {
 	u32_t tx_rdy      :1;
 	u32_t mode_delete :1; /*!< Operation mode of backspace key */
 	u32_t history_exit:1; /*!< Request to exit history mode */
+	u32_t last_nl     :8; /*!< Last received new line character */
 };
 
 BUILD_ASSERT_MSG((sizeof(struct shell_flags) == sizeof(u32_t)),
diff --git a/subsys/shell/shell.c b/subsys/shell/shell.c
index dfa444752d9..d551ad51cf2 100644
--- a/subsys/shell/shell.c
+++ b/subsys/shell/shell.c
@@ -698,12 +698,6 @@ static void shell_tab_handle(const struct shell *shell)
 	}
 }
 
-#define SHELL_ASCII_MAX_CHAR (127u)
-static inline int ascii_filter(const char data)
-{
-	return (u8_t) data > SHELL_ASCII_MAX_CHAR ? -EINVAL : 0;
-}
-
 static void metakeys_handle(const struct shell *shell, char data)
 {
 	/* Optional feature */
@@ -757,6 +751,29 @@ static void metakeys_handle(const struct shell *shell, char data)
 	}
 }
 
+/* Functions returns true if new line character shall be processed */
+static bool process_nl(const struct shell *shell, u8_t data)
+{
+	if ((data != '\r') && (data != '\n')) {
+		shell->ctx->internal.flags.last_nl = 0;
+		return false;
+	}
+
+	if ((shell->ctx->internal.flags.last_nl == 0) ||
+	    (data == shell->ctx->internal.flags.last_nl)) {
+		shell->ctx->internal.flags.last_nl = data;
+		return true;
+	}
+
+	return false;
+}
+
+#define SHELL_ASCII_MAX_CHAR (127u)
+static inline int ascii_filter(const char data)
+{
+	return (u8_t) data > SHELL_ASCII_MAX_CHAR ? -EINVAL : 0;
+}
+
 static void shell_state_collect(const struct shell *shell)
 {
 	size_t count = 0;
@@ -777,7 +794,7 @@ static void shell_state_collect(const struct shell *shell)
 
 		switch (shell->ctx->receive_state) {
 		case SHELL_RECEIVE_DEFAULT:
-			if ((data == '\r') || (data == '\n')) {
+			if (process_nl(shell, data)) {
 				if (!shell->ctx->cmd_buff_len) {
 					history_mode_exit(shell);
 					cursor_next_line_move(shell);
@@ -785,10 +802,13 @@ static void shell_state_collect(const struct shell *shell)
 					/* Command execution */
 					(void)shell_execute(shell);
 				}
-
+				/* Function responsible for printing prompt
+				 * on received NL.
+				 */
 				shell_state_set(shell, SHELL_STATE_ACTIVE);
 				return;
 			}
+
 			switch (data) {
 			case SHELL_VT100_ASCII_ESC: /* ESCAPE */
 				receive_state_change(shell, SHELL_RECEIVE_ESC);