Move the fallback on providers from backend to frontend.

This reverts commit e28973169d2e5eda8b64ebdda11ece0dc761d978.
This code might fit better in the frontend than in the backend finally.
Ref: http://www.archlinux.org/pipermail/pacman-dev/2007-November/010150.html

I also changed it for fixing FS#8763 :
if there is exactly one provider, pacman will pull it and print a warning.
if there are several providers, pacman will list them and fail. It's up to
the user to pick one. Add sync501 pactest to reflect that.

3 files changed, 48 insertions, 29 deletions

diff --git a/lib/libalpm/sync.c b/lib/libalpm/sync.c
index ec4af9f4..50de07ef 100644
--- a/lib/libalpm/sync.c
+++ b/lib/libalpm/sync.c
@@ -301,16 +301,7 @@ int _alpm_sync_addtarget(pmtrans_t *trans, pmdb_t *db_local, alpm_list_t *dbs_sy
 				repo_found = 1;
 				spkg = _alpm_db_get_pkgfromcache(db, targ);
 				if(spkg == NULL) {
-					/* Search provides */
-					_alpm_log(PM_LOG_DEBUG, "target '%s' not found in db '%s' -- looking for provisions\n", targ, db->treename);
-					alpm_list_t *p = _alpm_db_whatprovides(db, targ);
-					if(!p) {
-						RET_ERR(PM_ERR_PKG_NOT_FOUND, -1);
-					}
-					spkg = (pmpkg_t *) p->data;
-					_alpm_log(PM_LOG_DEBUG, "found '%s' as a provision for '%s'\n",
-							alpm_pkg_get_name(spkg), targ);
-					alpm_list_free(p);
+					RET_ERR(PM_ERR_PKG_NOT_FOUND, -1);
 				}
 			}
 		}
@@ -325,25 +316,10 @@ int _alpm_sync_addtarget(pmtrans_t *trans, pmdb_t *db_local, alpm_list_t *dbs_sy
 			spkg = _alpm_db_get_pkgfromcache(db, targ);
 		}
 		if(spkg == NULL) {
-			/* Search provides */
-			_alpm_log(PM_LOG_DEBUG, "target '%s' not found -- looking for provisions\n", targ);
-			for(j = dbs_sync; j && !spkg; j = j->next) {
-				pmdb_t *db = j->data;
-				alpm_list_t *p = _alpm_db_whatprovides(db, targ);
-				if(p) {
-					spkg = (pmpkg_t *) p->data;
-					_alpm_log(PM_LOG_DEBUG, "found '%s' as a provision for '%s' in db '%s'\n",
-							alpm_pkg_get_name(spkg), targ, db->treename);
-					alpm_list_free(p);
-				}
-			}
+			RET_ERR(PM_ERR_PKG_NOT_FOUND, -1);
 		}
 	}
 
-	if(spkg == NULL) {
-		RET_ERR(PM_ERR_PKG_NOT_FOUND, -1);
-	}
-
 	if(_alpm_pkg_should_ignore(spkg)) {
 		int resp;
 		QUESTION(trans, PM_TRANS_CONV_INSTALL_IGNOREPKG, spkg, NULL, NULL, &resp);
diff --git a/pactest/tests/sync501.py b/pactest/tests/sync501.py
new file mode 100644
index 00000000..fa5f3688
--- /dev/null
+++ b/pactest/tests/sync501.py
@@ -0,0 +1,15 @@
+self.description = "-S provision"
+
+sp = pmpkg("pkg1")
+sp.provides = ["provision 1.0-1"]
+self.addpkg2db("sync", sp)
+
+sp = pmpkg("pkg2")
+sp.provides = ["provision 1.0-1"]
+self.addpkg2db("sync", sp)
+
+self.args = "-S provision"
+
+self.addrule("PACMAN_RETCODE=1")
+self.addrule("!PKG_EXIST=pkg1")
+self.addrule("!PKG_EXIST=pkg2")
diff --git a/src/pacman/sync.c b/src/pacman/sync.c
index 00e8935f..c641dfec 100644
--- a/src/pacman/sync.c
+++ b/src/pacman/sync.c
@@ -605,9 +605,37 @@ static int sync_trans(alpm_list_t *targets, int sync_only)
 					}
 				}
 				if(!found) {
-					fprintf(stderr, _("error: '%s': not found in sync db\n"), targ);
-					retval = 1;
-					goto cleanup;
+					/* targ not found in sync db, searching for providers... */
+					alpm_list_t *prov = NULL;
+					for(j = sync_dbs; j; j = alpm_list_next(j)) {
+						pmdb_t *db = alpm_list_getdata(j);
+						prov = alpm_list_join(prov, alpm_db_whatprovides(db, targ));
+					}
+					if(prov != NULL) {
+						if(alpm_list_count(prov) == 1) {
+							const char *pname = NULL;
+							pmpkg_t *pkg = alpm_list_getdata(prov);
+							pname = alpm_pkg_get_name(pkg);
+							alpm_list_free(prov);
+							printf(_("Warning: %s provides %s\n"), pname, targ);
+							targets = alpm_list_add(targets, strdup(pname));
+						} else {
+							alpm_list_t *k;
+							fprintf(stderr, _("error: several packages provide %s, please specify one :\n"), targ);
+							for(k = prov; k; k = alpm_list_next(k)) {
+								pmpkg_t *pkg = alpm_list_getdata(k);
+								printf("%s ", alpm_pkg_get_name(pkg));
+							}
+							printf("\n");
+							alpm_list_free(prov);
+							retval = 1;
+							goto cleanup;
+						}
+					} else {
+						fprintf(stderr, _("error: '%s': not found in sync db\n"), targ);
+						retval = 1;
+						goto cleanup;
+					}
 				}
 			}
 		}