user specs [.key?]

Fixes: ticket:984

3 files changed, 26 insertions, 4 deletions

diff --git a/doc/configuration/specs.html.part b/doc/configuration/specs.html.part
index 9903a35a0..79f75f21d 100644
--- a/doc/configuration/specs.html.part
+++ b/doc/configuration/specs.html.part
@@ -32,6 +32,7 @@ the following order:</p>
     <li><code>[=1.23]</code>: Match a particular version. Any operator described below
     can be used. May be extended to ranged dependencies, using either <code>[=1.23|=1.24|=1.25]</code> for an or
     dependency or <code>[&gt;=1.2&amp;&lt;2]</code> for an and dependency.</li>
+    <li><code>[.key?]</code>: Match only if the specified metadata key exists.</li>
     <li><code>[.key=value]</code>: Match only if the specified metadata key has a particular exact value. Only works for
     simple values, sets and sequences, not spec trees and other complex compound keys. If <code>&lt;</code> is used in
     place of <code>=</code>, for numeric values a less-than comparison is used, and for sets, sequences and spec trees,
diff --git a/paludis/user_dep_spec.cc b/paludis/user_dep_spec.cc
index ed516e064..600f50abb 100644
--- a/paludis/user_dep_spec.cc
+++ b/paludis/user_dep_spec.cc
@@ -356,13 +356,16 @@ namespace paludis
 
         Imp(const std::string & s)
         {
-            std::string::size_type p(s.find_first_of("=<>"));
+            std::string::size_type p(s.find_first_of("=<>?"));
             if (std::string::npos == p)
-                throw PackageDepSpecError("Expected an =, a < or a > inside '[." + s + "]'");
+                throw PackageDepSpecError("Expected an =, a <, a > or a ? inside '[." + s + "]'");
 
             key = s.substr(0, p);
             value = s.substr(p + 1);
             op = s.at(p);
+
+            if (op == '?' && ! value.empty())
+                throw PackageDepSpecError("Operator '?' takes no value inside '[." + s + "]'");
         }
     };
 }
@@ -759,8 +762,13 @@ UserKeyRequirement::requirement_met(const Environment * const, const ChangedChoi
     if (m == id.end_metadata())
         return std::make_pair(false, as_human_string());
 
-    KeyComparator c(_imp->value, _imp->op);
-    return std::make_pair((*m)->accept_returning<bool>(c), as_human_string());
+    if (_imp->op == '?')
+        return std::make_pair(true, as_human_string());
+    else
+    {
+        KeyComparator c(_imp->value, _imp->op);
+        return std::make_pair((*m)->accept_returning<bool>(c), as_human_string());
+    }
 }
 
 const std::string
@@ -774,6 +782,8 @@ UserKeyRequirement::as_human_string() const
             return "Key '" + _imp->key + "' contains or is less than '" + _imp->value + "'";
         case '>':
             return "Key '" + _imp->key + "' is greater than '" + _imp->value + "'";
+        case '?':
+            return "Key '" + _imp->key + "' exists";
     }
 
     throw InternalError(PALUDIS_HERE, "unknown op");
diff --git a/paludis/user_dep_spec_TEST.cc b/paludis/user_dep_spec_TEST.cc
index 5d024047e..d1950af8b 100644
--- a/paludis/user_dep_spec_TEST.cc
+++ b/paludis/user_dep_spec_TEST.cc
@@ -225,6 +225,11 @@ namespace test_cases
 
             PackageDepSpec p(parse_user_package_dep_spec("foo/bar[.key=value]", &env, { }));
             check_spec(p, "foo/bar", "", "", "", "", "", "", "", "[.key=value]");
+
+            TEST_CHECK_THROWS(parse_user_package_dep_spec("=foo/bar[.foo?q]", &env, { }), PackageDepSpecError);
+
+            PackageDepSpec q(parse_user_package_dep_spec("foo/bar[.foo?]", &env, { }));
+            check_spec(q, "foo/bar", "", "", "", "", "", "", "", "[.foo?]");
         }
     } test_user_package_dep_spec;
 
@@ -468,6 +473,12 @@ namespace test_cases
 
             PackageDepSpec l(parse_user_package_dep_spec("cat/pkg1[.HITCHHIKER>41]", &env, { }));
             TEST_CHECK(match_package(env, l, *pkg1, { }));
+
+            PackageDepSpec m(parse_user_package_dep_spec("cat/pkg1[.HITCHHIKER?]", &env, { }));
+            TEST_CHECK(match_package(env, m, *pkg1, { }));
+
+            PackageDepSpec n(parse_user_package_dep_spec("cat/pkg1[.SPOON?]", &env, { }));
+            TEST_CHECK(! match_package(env, n, *pkg1, { }));
         }
     } test_user_package_dep_spec_user_key_req;
 }