Sending patch for new feat: placeholders in execute command

From 81b020a3d10c7494145aca23c2e9544b9e0b5384 Mon Sep 17 00:00:00 2001
From: Luca Coraggio <[email protected]>
Date: Sat, 1 Nov 2025 19:05:39 +0100
Subject: [PATCH] Add alloc_and_parse_command (file.c), add cmdplacholders
 structure (definitions.h), updated docs

Rationale -- this commit adds the following new feature: execute command can now use
 placeholders that get replaced with current file information (filename, filetype, or current
 working dir). This enables the user to use external commands (e.g. shell filters) that work
 conditionally on file-specific information. File-specific external commands extend the idea of
 syntax-specific linter and formatter, greatly enhancing nano's flexibility in handling
 different file types, by exposing information information that is already available within nano
 internals, with as little modifications as possible.

Signed-off-by: Luca Coraggio <[email protected]>
---
 doc/nano.texi     |  5 +++
 doc/nanorc.5      |  5 +++
 src/definitions.h | 10 +++++
 src/files.c       | 95 ++++++++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 114 insertions(+), 1 deletion(-)

diff --git a/doc/nano.texi b/doc/nano.texi
index 1374094d..4846221e 100644
--- a/doc/nano.texi
+++ b/doc/nano.texi
@@ -1580,6 +1580,11 @@ into the current buffer --- or into a new buffer when @kbd{M-F} is toggled.
 When the program's name is preceded by a pipe symbol (@kbd{|}), then the
 current buffer (or the marked region) is piped to the program, and the
 output of the program replaces the buffer (or the marked region).
+Placeholders can be used in the prompt to access current file information.
+Available placeholders are: @code{\FNAME} (replaced with the current file
+name as shown in the title bar); @code{\FTYPE} (replaced with the current
+file type); @code{\CWD} (replaced with the current working directory).
+Placeholders can be escaped with @code{\} (e.g. @code{\\FTYPE}).
 
 @item speller
 Invokes a spell-checking program, either the default @command{hunspell}
diff --git a/doc/nanorc.5 b/doc/nanorc.5
index b7c3d328..dab72c26 100644
--- a/doc/nanorc.5
+++ b/doc/nanorc.5
@@ -723,6 +723,11 @@ into the current buffer \(em or into a new buffer when \fBM\-F\fR is toggled.
 When the program's name is preceded by a pipe symbol (\fB|\fR), then the
 current buffer (or the marked region) is piped to the program, and the
 output of the program replaces the buffer (or the marked region).
+Placeholders can be used in the prompt to access current file information.
+Available placeholders are: \fB\\FNAME\fR (replaced with the current file name as
+shown in the title bar); \fB\\FTYPE\fR (replaced with the current file type);
+\fB\\CWD\fR (replaced with the current working directory). Placeholder can be
+escaped with \fB\\\fR (e.g., \fB\\\\FNAME\fR).
 .TP
 .B speller
 Invokes a spell-checking program, either the default \fBhunspell\fR(1) or GNU
diff --git a/src/definitions.h b/src/definitions.h
index c73b4a82..daa5dc5d 100644
--- a/src/definitions.h
+++ b/src/definitions.h
@@ -662,3 +662,13 @@ typedef struct completionstruct {
 	struct completionstruct *next;
 } completionstruct;
 #endif
+
+#ifndef NANO_TINY
+typedef struct cmdplaceholders {
+	/* Define placeholders strings that gets substituted in execute commands */
+		const char *placeholder;
+			/* The string that is replaced if found in execute command */
+		const char *replacement;
+			/* The replacement value for placeholder */
+} cmdplaceholders;
+#endif
diff --git a/src/files.c b/src/files.c
index da397e6b..fdbc2649 100644
--- a/src/files.c
+++ b/src/files.c
@@ -1012,6 +1012,97 @@ void send_data(const linestruct *line, int fd)
 	fclose(tube);
 }
 
+
+#ifndef NANO_TINY
+char *alloc_and_parse_command(const char *given)
+{
+	if (!given) return copy_of("");
+
+	char *cwd = getcwd(NULL, 0); /* alloc */
+
+	/* Set available placeholders */
+	const cmdplaceholders placeholders[] = {
+		{"\\FNAME", openfile? (openfile->filename ? openfile->filename : "") : "" },
+		{"\\FTYPE", openfile? (openfile->syntax ? openfile->syntax->name : "") : "" },
+		{"\\CWD", cwd ? cwd : ""},
+	};
+
+
+	/* Initialize auxiliary information on placeholder and offsets */
+	size_t num_placeholders = sizeof(placeholders) / sizeof(placeholders[0]);
+	size_t len_placeholders[num_placeholders];
+	size_t len_replacements[num_placeholders];
+	ssize_t len_offsets[num_placeholders];
+
+	for (int i=0; i<num_placeholders; i++){
+		len_placeholders[i] = strlen(placeholders[i].placeholder);
+		len_replacements[i] = strlen(placeholders[i].replacement);
+		len_offsets[i] = len_replacements[i] - len_placeholders[i];
+	}
+
+	ssize_t len_output = (ssize_t)strlen(given);
+
+	/* Pass once through the given command to find placeholders and
+	   compute the length required for the output string */
+	const char *p = given;
+	while (*p) {
+		if ( *p=='\\' ){
+			if (*(p+1)=='\\') {
+				/* Two backslashes escape the placeholder */
+				p += 2;   /* Skip to the next char after the second backslash */
+				continue;
+			}
+			bool matched = FALSE;
+			for (size_t i=0; i<num_placeholders; i++){
+				if (0==strncmp(p, placeholders[i].placeholder, len_placeholders[i])) {
+					matched = TRUE;
+					len_output += len_offsets[i];
+					p += len_placeholders[i];
+					break;
+				}
+			}
+			if (!matched) p++;
+		}
+		else p++;
+	}
+
+	/* Second pass on given: copy string substituting placeholders or escaped placeholders*/
+	if ( (len_output<=0) || (len_output > SSIZE_MAX - 1) ) return copy_of(given);
+
+	char *output = nmalloc(len_output + 1); /* +1 for the null terminator */
+	char *o = output;
+	while (*given){
+		if (*given=='\\'){
+			if ( *(given+1)=='\\' ) {
+				/* Escaped */
+				*o++ = *given++;
+				*o++ = *given++;
+			} else {
+				bool matched = FALSE;
+				for (size_t i=0; i<num_placeholders; i++){
+					if (0==strncmp(given, placeholders[i].placeholder, len_placeholders[i])) {
+					        given += len_placeholders[i];
+					        memcpy(o, placeholders[i].replacement, len_replacements[i]);
+					        o += len_replacements[i];
+					        matched = TRUE;
+						break;
+					}
+				}
+				if (!matched) *o++ = *given++;
+			}
+		}
+		else *o++ = *given++;
+	}
+	*o = '\0';
+
+	if(cwd) free(cwd);
+
+	return output;
+}
+#endif
+
+
+
 /* Execute the given command in a shell. */
 void execute_command(const char *command)
 {
@@ -1318,7 +1409,9 @@ void insert_a_file_or(bool execute)
 				/* If the command is not empty, execute it and read its output
 				 * into the buffer, and add the command to the history list. */
 				if (*answer != '\0') {
-					execute_command(answer);
+					char *parsed_command = alloc_and_parse_command(answer);
+					execute_command(parsed_command);
+					free(parsed_command);
 #ifdef ENABLE_HISTORIES
 					update_history(&execute_history, answer, PRUNE_DUPLICATE);
 #endif
-- 
2.51.0