add --preremove option

Allows adding and removing packages within a single transaction. This is
particularly useful for complicated conflicts that ALPM cannot resolve
on its own, e.g.:

https://archlinux.org/news/linux-firmware-2025061312fe085f-5-upgrade-requires-manual-intervention/

Currently, dealing with these situations requires doing something
complicated like bypassing dependency checking to break and then repair
the database in two separate steps. By allowing installation and removal
within a single transaction no bypass is required:

 pacman -Syu --preremove linux-firmware linux-firmware

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>

doc/pacman.8.asciidoc

@@ -292,6 +292,9 @@ Upgrade Options (apply to '-S' and '-U')[[UO]]
 	exclamation mark. Subsequent matches will override previous ones. A leading
 	literal exclamation mark or backslash needs to be escaped.
 
+*\--preremove <package>::
+	Uninstall 'package' before performing the requested installation. Multiple
+	packages can be specified by separating them with commas.
 
 Query Options (apply to '-Q')[[QO]]
 -----------------------------------

lib/libalpm/dload.c

@@ -1118,34 +1118,31 @@ static int finalize_download_locations(alpm_list_t *payloads, const char *localp
 			filename = payload->tempfile_name;
 		}
 
-		if(filename) {
+		/* if neither file exists then the download failed and logged an error for us */
+		if(!filename) {
+			returnvalue = -1;
+			continue;
+		}
+
 		int ret = move_file(filename, localpath);
 
 		if(ret == -1) {
+			/* ignore error if the file already existed - only signature file was downloaded */
 			if(payload->mtime_existing_file == 0) {
 				_alpm_log(payload->handle, ALPM_LOG_ERROR, _("could not move %s into %s (%s)\n"),
 						filename, localpath, strerror(errno));
 				returnvalue = -1;
 			}
 		}
-		}
 
 		if (payload->download_signature) {
-			char *sig_filename;
-			int ret;
-
-			filename = payload->destfile_name ? payload->destfile_name : payload->tempfile_name;
-			sig_filename = _alpm_get_fullpath("", filename, ".sig");
-			ASSERT(sig_filename, RET_ERR(payload->handle, ALPM_ERR_MEMORY, -1));
-			ret = move_file(sig_filename, localpath);
-			free(sig_filename);
-
-			if(ret == -1) {
-				sig_filename = _alpm_get_fullpath("", filename, ".sig.part");
-				ASSERT(sig_filename, RET_ERR(payload->handle, ALPM_ERR_MEMORY, -1));
+			const char sig_suffix[] = ".sig";
+			char *sig_filename = NULL;
+			size_t sig_filename_len = strlen(filename) + sizeof(sig_suffix);
+			MALLOC(sig_filename, sig_filename_len, continue);
+			snprintf(sig_filename, sig_filename_len, "%s%s", filename, sig_suffix);
 			move_file(sig_filename, localpath);
-				free(sig_filename);
-			}
+			FREE(sig_filename);
 		}
 	}
 	return returnvalue;
@@ -1299,7 +1296,7 @@ download_signature:
 	return ret;
 }
 
-static const char *url_basename(const char *url)
+static char *filecache_find_url(alpm_handle_t *handle, const char *url)
 {
 	const char *filebase = strrchr(url, '/');
 
@@ -1312,7 +1309,7 @@ static const char *url_basename(const char *url)
 		return NULL;
 	}
 
-	return filebase;
+	return _alpm_filecache_find(handle, filebase);
 }
 
 int SYMEXPORT alpm_fetch_pkgurl(alpm_handle_t *handle, const alpm_list_t *urls,
@@ -1334,26 +1331,9 @@ int SYMEXPORT alpm_fetch_pkgurl(alpm_handle_t *handle, const alpm_list_t *urls,
 
 	for(i = urls; i; i = i->next) {
 		char *url = i->data;
-		char *filepath = NULL;
-		const char *urlbase = url_basename(url);
 
-		if(urlbase) {
 		/* attempt to find the file in our pkgcache */
-			filepath = _alpm_filecache_find(handle, urlbase);
-
-			if(filepath && (handle->siglevel & ALPM_SIG_PACKAGE)) {
-				char *sig_filename = _alpm_get_fullpath("", urlbase, ".sig");
-
-				/* if there's no .sig file then forget about the pkg file and go for download */
-				if(!_alpm_filecache_exists(handle, sig_filename)) {
-					free(filepath);
-					filepath = NULL;
-				}
-
-				free(sig_filename);
-			}
-		}
-
+		char *filepath = filecache_find_url(handle, url);
 		if(filepath) {
 			/* the file is locally cached so add it to the output right away */
 			alpm_list_append(fetched, filepath);

scripts/libmakepkg/lint_pkgbuild/meson.build

@@ -17,6 +17,7 @@ sources = [
   'package_function.sh.in',
   'package_function_variable.sh.in',
   'pkgbase.sh.in',
+  'pkglist.sh.in',
   'pkgname.sh.in',
   'pkgrel.sh.in',
   'pkgver.sh.in',

scripts/libmakepkg/lint_pkgbuild/pkglist.sh.in

@@ -0,0 +1,44 @@
+#!/bin/bash
+#
+#   pkglist.sh - Check the packages selected to build exist.
+#
+#   Copyright (c) 2014-2025 Pacman Development Team <pacman-dev@lists.archlinux.org>
+#
+#   This program is free software; you can redistribute it and/or modify
+#   it under the terms of the GNU General Public License as published by
+#   the Free Software Foundation; either version 2 of the License, or
+#   (at your option) any later version.
+#
+#   This program is distributed in the hope that it will be useful,
+#   but WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#   GNU General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+[[ -n "$LIBMAKEPKG_LINT_PKGBUILD_PKGLIST_SH" ]] && return
+LIBMAKEPKG_LINT_PKGBUILD_PKGLIST_SH=1
+
+MAKEPKG_LIBRARY=${MAKEPKG_LIBRARY:-'@libmakepkgdir@'}
+
+source "$MAKEPKG_LIBRARY/util/message.sh"
+source "$MAKEPKG_LIBRARY/util/util.sh"
+
+
+lint_pkgbuild_functions+=('lint_pkglist')
+
+
+lint_pkglist() {
+	local i ret=0
+
+	for i in "${PKGLIST[@]}"; do
+		if ! in_array "$i" "${pkgname[@]}"; then
+			error "$(gettext "Requested package %s is not provided in %s")" "$i" "$BUILDFILE"
+			ret=1
+		fi
+	done
+
+	return $ret
+}

src/pacman/conf.c

@@ -150,6 +150,7 @@ int config_free(config_t *oldconfig)
 	FREELIST(oldconfig->noupgrade);
 	FREELIST(oldconfig->noextract);
 	FREELIST(oldconfig->overwrite_files);
+	FREELIST(oldconfig->preremove);
 	free(oldconfig->configfile);
 	free(oldconfig->sysroot);
 	free(oldconfig->rootdir);

src/pacman/conf.h

@@ -134,6 +134,8 @@ typedef struct __config_t {
 	/* our connection to libalpm */
 	alpm_handle_t *handle;
 
+	alpm_list_t *preremove;
+
 	alpm_list_t *explicit_adds;
 	alpm_list_t *explicit_removes;
 
@@ -214,7 +216,8 @@ enum {
 	OP_REFRESH,
 	OP_ASSUMEINSTALLED,
 	OP_DISABLEDLTIMEOUT,
-	OP_DISABLESANDBOX
+	OP_DISABLESANDBOX,
+	OP_PREREMOVE,
 };
 
 /* clean method */

src/pacman/pacman.c

@@ -196,6 +196,8 @@ static void usage(int op, const char * const myname)
 				addlist(_("      --ignore <pkg>   ignore a package upgrade (can be used more than once)\n"));
 				addlist(_("      --ignoregroup <grp>\n"
 				          "                       ignore a group upgrade (can be used more than once)\n"));
+				addlist(_("      --preremove <pkg>\n"));
+				addlist(_("                       uninstall <pkg> before performing installation\n"));
 				__attribute__((fallthrough));
 			case PM_OP_REMOVE:
 				addlist(_("  -d, --nodeps         skip dependency version checks (-dd to skip all checks)\n"));
@@ -770,6 +772,9 @@ static int parsearg_upgrade(int opt)
 		case OP_IGNOREGROUP:
 			parsearg_util_addlist(&(config->ignoregrp));
 			break;
+		case OP_PREREMOVE:
+			parsearg_util_addlist(&(config->preremove));
+			break;
 		case OP_DOWNLOADONLY:
 		case 'w':
 			config->op_s_downloadonly = 1;
@@ -982,6 +987,7 @@ static int parseargs(int argc, char *argv[])
 		{"color",      required_argument, 0, OP_COLOR},
 		{"disable-download-timeout", no_argument, 0, OP_DISABLEDLTIMEOUT},
 		{"disable-sandbox", no_argument, 0, OP_DISABLESANDBOX},
+		{"preremove", required_argument, 0, OP_PREREMOVE},
 		{0, 0, 0, 0}
 	};
 

src/pacman/sync.c

@@ -717,6 +717,21 @@ static int sync_trans(alpm_list_t *targets)
 		}
 	}
 
+	for(i = config->preremove; i; i = i->next) {
+		alpm_pkg_t *pkg;
+		const char *pname = i->data;
+		alpm_db_t *db_local = alpm_get_localdb(config->handle);
+
+		if((pkg = alpm_db_get_pkg(db_local, pname)) != NULL) {
+			if(alpm_remove_pkg(config->handle, pkg) == -1) {
+				alpm_errno_t err = alpm_errno(config->handle);
+				pm_printf(ALPM_LOG_ERROR, "'%s': %s\n", pname, alpm_strerror(err));
+				retval = 1;
+			}
+			config->explicit_removes = alpm_list_add(config->explicit_removes, pkg);
+		}
+	}
+
 	if(retval) {
 		trans_release();
 		return retval;