qpkg: detect conflicts with installed packages

- prereq.c (installed_conflicts, free_conflicts, prereq): collect list of
  pre-existing conflicts in installed packages
- prereq.c (prereq): check if package being requested already conflicts
- test/instconf: regression test for conflicts with installed packages
- TODO: updated for full support of conflicts. Mention that we're not
  terribly efficient with handling conflicts.

qpkg/TODO

@@ -1,12 +1,8 @@
 Still left to do
 ================
 
-- check whether introducing a new package would cause a conflict
-
-  Update: conflicts among the packages considered for installation are now
-  checked.
-
-- compile the list of conflicts of installed packages
+- consider reducing the size of the lists of conflicts, e.g., by making
+  them unique via a red-black tree
 
 - handle Provides:
 
@@ -53,3 +49,10 @@ Done
   1172642 calls to comp_id, or 102% of the predicted "good case".
 
 - if there are multiple choices, try to prefer more recent versions
+
+- check whether introducing a new package would cause a conflict
+
+  Update: conflicts among the packages considered for installation are now
+  checked.
+
+- compile the list of conflicts of installed packages

qpkg/prereq.c

@@ -16,9 +16,9 @@
 #include <string.h>
 #include <assert.h>
 
+#include "util.h"
 #include "id.h"
 #include "qpkg.h"
-#include "util.h"
 #include "prereq.h"
 
 
@@ -221,6 +221,42 @@ static void resolve(struct list *next_dep, const struct ref *dep,
 }
 
 
+static struct list *installed_conflicts(void)
+{
+	struct list *list = NULL, *new;
+	const struct jrb *n;
+	const struct pkg *pkg;
+	
+	for (n = jrb_first(packages->root); n != jrb_nil(packages->root);
+	    n = jrb_next(n)) {
+		pkg = n->val;
+		if (!pkg)
+			continue;
+		if (!(pkg->flags & QPKG_INSTALLED))
+			continue;
+		if (!pkg->conflicts)	/* optimization */
+			continue;
+		new = alloc_type(struct list);
+		new->refs = pkg->conflicts;
+		new->next = list;
+		list = new;
+	}
+	return list;
+}
+
+
+static void free_conflicts(struct list *conf)
+{
+	struct list *next;
+
+	while (conf) {
+		next = conf->next;
+		free(conf);
+		conf = next;
+	}
+}
+
+
 struct pkg **prereq(struct pkg *pkg)
 {
 	struct stack stack = {
@@ -229,13 +265,18 @@ struct pkg **prereq(struct pkg *pkg)
 	};
 	struct list conf = {
 		.refs = pkg->conflicts,
-		.next = NULL
+		.next = installed_conflicts()
 	};
 
-	/* @@@ make list of pre-existing conflicts */
+	if (conflicts(pkg, &conf)) {
+		fprintf(stderr, "%.*s conflicts with installed packages\n",
+		  ID2PF(pkg->id));
+		exit(1);
+	}
 	pkg->flags |= QPKG_ADDING;
 	resolve(NULL, pkg->depends, &stack, &conf);
 	pkg->flags &= ~QPKG_ADDING;
 	free(installs);
+	free_conflicts(conf.next);
 	return best;
 }

qpkg/test/instconf

@@ -0,0 +1,50 @@
+#!/bin/sh
+. ./Common
+
+###############################################################################
+
+qpkg_fail "installed package conflicts with dependency" prereq A <<EOF
+Package: B
+Version: 0
+Architecture: test
+Filename: B
+
+Package: A
+Version: 0
+Architecture: test
+Depends: B
+Filename: A
+
+Package: C
+Version: 0
+Architecture: test
+Conflicts: B
+Status: installed
+EOF
+expect <<EOF
+can't resolve A
+EOF
+
+###############################################################################
+
+qpkg_fail "installed package conflicts with initial package" prereq A <<EOF
+Package: B
+Version: 0
+Architecture: test
+Filename: B
+
+Package: A
+Version: 0
+Architecture: test
+Depends: B
+Filename: A
+
+Package: C
+Version: 0
+Architecture: test
+Conflicts: A
+Status: installed
+EOF
+expect <<EOF
+A conflicts with installed packages
+EOF