Implement info meta operation

This meta operation can be used to print basic information (name, version,
source/output roots, etc) for one or more projects.

24 files changed, 227 insertions, 71 deletions

diff --git a/build2/b.cli b/build2/b.cli
index 8148702..724a676 100644
--- a/build2/b.cli
+++ b/build2/b.cli
@@ -276,7 +276,20 @@ namespace build2
      \li|\cb{dist}
 
          Prepare a distribution containing all files necessary to perform all
-         operations in a project. Implemented by the \cb{dist} module.||
+         operations in a project. Implemented by the \cb{dist} module.|
+
+     \li|\cb{info}
+
+         Print basic information (name, version, source and output
+         directories, etc) about one or more projects to \cb{STDOUT},
+         separating multiple projects with a blank line. Each project is
+         identified by its root directory target. For example:
+
+         \
+         b info: libfoo/ libbar/
+         \
+
+         ||
 
      The build system has the following built-in and pre-defined operations:
 
diff --git a/build2/config/init.cxx b/build2/config/init.cxx
index 040aeca..7285671 100644
--- a/build2/config/init.cxx
+++ b/build2/config/init.cxx
@@ -53,8 +53,8 @@ namespace build2
       // Register meta-operations. Note that we don't register create_id
       // since it will be pre-processed into configure.
       //
-      rs.meta_operations.insert (configure_id, configure);
-      rs.meta_operations.insert (disfigure_id, disfigure);
+      rs.meta_operations.insert (configure_id, mo_configure);
+      rs.meta_operations.insert (disfigure_id, mo_disfigure);
 
       auto& vp (var_pool.rw (rs));
 
diff --git a/build2/config/operation.cxx b/build2/config/operation.cxx
index 2fad6b0..64919f8 100644
--- a/build2/config/operation.cxx
+++ b/build2/config/operation.cxx
@@ -395,7 +395,7 @@ namespace build2
       }
     }
 
-    const meta_operation_info configure {
+    const meta_operation_info mo_configure {
       configure_id,
       "configure",
       "configure",
@@ -624,7 +624,7 @@ namespace build2
       }
     }
 
-    const meta_operation_info disfigure {
+    const meta_operation_info mo_disfigure {
       disfigure_id,
       "disfigure",
       "disfigure",
@@ -807,7 +807,7 @@ namespace build2
       }
 
       params.clear ();
-      return configure.name;
+      return mo_configure.name;
     }
   }
 }
diff --git a/build2/config/operation.hxx b/build2/config/operation.hxx
index bf9403f..1317d38 100644
--- a/build2/config/operation.hxx
+++ b/build2/config/operation.hxx
@@ -14,8 +14,8 @@ namespace build2
 {
   namespace config
   {
-    extern const meta_operation_info configure;
-    extern const meta_operation_info disfigure;
+    extern const meta_operation_info mo_configure;
+    extern const meta_operation_info mo_disfigure;
 
     const string&
     preprocess_create (const variable_overrides&,
diff --git a/build2/context.cxx b/build2/context.cxx
index b12920c..c4688be 100644
--- a/build2/context.cxx
+++ b/build2/context.cxx
@@ -386,6 +386,7 @@ namespace build2
     meta_operation_table.insert (
       meta_operation_data ("create", &config::preprocess_create));
     meta_operation_table.insert ("dist");
+    meta_operation_table.insert ("info");
 
     operation_table.clear ();
     operation_table.insert ("default");
diff --git a/build2/context.hxx b/build2/context.hxx
index fed6bf1..d2daad6 100644
--- a/build2/context.hxx
+++ b/build2/context.hxx
@@ -258,6 +258,8 @@ namespace build2
 
   // Cached variables.
   //
+  // Note: consider printing in info meta-operation if adding anything here.
+  //
   extern const variable* var_src_root;
   extern const variable* var_out_root;
   extern const variable* var_src_base;
diff --git a/build2/dist/init.cxx b/build2/dist/init.cxx
index d002868..33ddcd7 100644
--- a/build2/dist/init.cxx
+++ b/build2/dist/init.cxx
@@ -32,7 +32,7 @@ namespace build2
 
       // Register meta-operation.
       //
-      rs.meta_operations.insert (dist_id, dist);
+      rs.meta_operations.insert (dist_id, mo_dist);
 
       // Enter module variables. Do it during boot in case they get assigned
       // in bootstrap.build (which is customary for, e.g., dist.package).
diff --git a/build2/dist/operation.cxx b/build2/dist/operation.cxx
index 6692156..d63e483 100644
--- a/build2/dist/operation.cxx
+++ b/build2/dist/operation.cxx
@@ -54,12 +54,6 @@ namespace build2
     }
 
     static void
-    dist_match (const values&, action, action_targets&)
-    {
-      // Don't match anything -- see execute ().
-    }
-
-    static void
     dist_execute (const values&, action, action_targets& ts, bool)
     {
       tracer trace ("dist_execute");
@@ -249,8 +243,8 @@ namespace build2
       // Make sure what we need to distribute is up to date.
       //
       {
-        if (perform.meta_operation_pre != nullptr)
-          perform.meta_operation_pre (params, loc);
+        if (mo_perform.meta_operation_pre != nullptr)
+          mo_perform.meta_operation_pre (params, loc);
 
         // This is a hack since according to the rules we need to completely
         // reset the state. We could have done that (i.e., saved target names
@@ -259,24 +253,24 @@ namespace build2
         // the dist mete-opreation is "compatible" with perform).
         //
         size_t on (current_on);
-        set_current_mif (perform);
+        set_current_mif (mo_perform);
         current_on = on + 1;
 
-        if (perform.operation_pre != nullptr)
-          perform.operation_pre (params, update_id);
+        if (mo_perform.operation_pre != nullptr)
+          mo_perform.operation_pre (params, update_id);
 
-        set_current_oif (update);
+        set_current_oif (op_update);
 
         action a (perform_id, update_id);
 
-        perform.match (params, a, files);
-        perform.execute (params, a, files, true); // Run quiet.
+        mo_perform.match (params, a, files);
+        mo_perform.execute (params, a, files, true); // Run quiet.
 
-        if (perform.operation_post != nullptr)
-          perform.operation_post (params, update_id);
+        if (mo_perform.operation_post != nullptr)
+          mo_perform.operation_post (params, update_id);
 
-        if (perform.meta_operation_post != nullptr)
-          perform.meta_operation_post (params);
+        if (mo_perform.meta_operation_post != nullptr)
+          mo_perform.meta_operation_post (params);
       }
 
       dir_path td (dist_root / dir_path (dist_package));
@@ -525,7 +519,7 @@ namespace build2
       }
     }
 
-    const meta_operation_info dist {
+    const meta_operation_info mo_dist {
       dist_id,
       "dist",
       "distribute",
@@ -536,7 +530,7 @@ namespace build2
       &dist_operation_pre,
       &load,   // normal load
       &search, // normal search
-      &dist_match,
+      nullptr, // no match (see execute()).
       &dist_execute,
       nullptr, // operation post
       nullptr  // meta-operation post
diff --git a/build2/dist/operation.hxx b/build2/dist/operation.hxx
index c72e467..0639688 100644
--- a/build2/dist/operation.hxx
+++ b/build2/dist/operation.hxx
@@ -14,7 +14,7 @@ namespace build2
 {
   namespace dist
   {
-    extern const meta_operation_info dist;
+    extern const meta_operation_info mo_dist;
   }
 }
 
diff --git a/build2/file.cxx b/build2/file.cxx
index 1ad3500..edd3e28 100644
--- a/build2/file.cxx
+++ b/build2/file.cxx
@@ -38,6 +38,23 @@ namespace build2
   //
   const path config_file (build_dir / "config.build");
 
+  ostream&
+  operator<< (ostream& os, const subprojects& sps)
+  {
+    for (auto b (sps.begin ()), i (b); os && i != sps.end (); ++i)
+    {
+      // See find_subprojects() for details.
+      //
+      const string& n (path::traits::is_separator (i->first.back ())
+                       ? empty_string
+                       : i->first);
+
+      os << (i != b ? " " : "") << n << '@' << i->second;
+    }
+
+    return os;
+  }
+
   bool
   is_src_root (const dir_path& d)
   {
@@ -151,12 +168,13 @@ namespace build2
     //
     if (first)
     {
-      rs.meta_operations.insert (noop_id, noop);
-      rs.meta_operations.insert (perform_id, perform);
+      rs.meta_operations.insert (noop_id, mo_noop);
+      rs.meta_operations.insert (perform_id, mo_perform);
+      rs.meta_operations.insert (info_id, mo_info);
 
-      rs.operations.insert (default_id, default_);
-      rs.operations.insert (update_id, update);
-      rs.operations.insert (clean_id, clean);
+      rs.operations.insert (default_id, op_default);
+      rs.operations.insert (update_id, op_update);
+      rs.operations.insert (clean_id, op_clean);
     }
 
     // If this is already a root scope, verify that things are
@@ -486,10 +504,10 @@ namespace build2
       // 'project' variable stays empty, here we come up with a surrogate
       // name for a key. The idea is that such a key should never conflict
       // with a real project name. We ensure this by using the project's
-      // sub-directory and appending trailing '/' to it.
+      // sub-directory and appending a trailing directory separator to it.
       //
       if (name.empty ())
-        name = dir.posix_string () + '/';
+        name = dir.posix_string () + path::traits::directory_separator;
 
       // @@ Can't use move() because we may need the values in diagnostics
       // below. Looks like C++17 try_emplace() is what we need.
diff --git a/build2/file.hxx b/build2/file.hxx
index d946c88..f334d8c 100644
--- a/build2/file.hxx
+++ b/build2/file.hxx
@@ -21,6 +21,9 @@ namespace build2
 
   using subprojects = std::map<string, dir_path>;
 
+  ostream&
+  operator<< (ostream&, const subprojects&); // Print as name@dir sequence.
+
   extern const dir_path build_dir;     // build
   extern const dir_path bootstrap_dir; // build/bootstrap
 
diff --git a/build2/install/init.cxx b/build2/install/init.cxx
index b5fd007..3e4e1ff 100644
--- a/build2/install/init.cxx
+++ b/build2/install/init.cxx
@@ -142,8 +142,8 @@ namespace build2
 
       // Register the install and uninstall operations.
       //
-      r.operations.insert (install_id, install);
-      r.operations.insert (uninstall_id, uninstall);
+      r.operations.insert (install_id,   op_install);
+      r.operations.insert (uninstall_id, op_uninstall);
     }
 
     static const path cmd ("install");
diff --git a/build2/install/operation.cxx b/build2/install/operation.cxx
index 5405c63..5279b3d 100644
--- a/build2/install/operation.cxx
+++ b/build2/install/operation.cxx
@@ -28,7 +28,7 @@ namespace build2
     // those things get racy. Also, since all we do here is creating/removing
     // files, there is not going to be much speedup from doing it in parallel.
 
-    const operation_info install {
+    const operation_info op_install {
       install_id,
       "install",
       "install",
@@ -50,7 +50,7 @@ namespace build2
     // link.exe only creates a DLL's import library if there are any exported
     // symbols).
     //
-    const operation_info uninstall {
+    const operation_info op_uninstall {
       uninstall_id,
       "uninstall",
       "uninstall",
diff --git a/build2/install/operation.hxx b/build2/install/operation.hxx
index 1529621..0d96faf 100644
--- a/build2/install/operation.hxx
+++ b/build2/install/operation.hxx
@@ -14,8 +14,8 @@ namespace build2
 {
   namespace install
   {
-    extern const operation_info install;
-    extern const operation_info uninstall;
+    extern const operation_info op_install;
+    extern const operation_info op_uninstall;
   }
 }
 
diff --git a/build2/name.cxx b/build2/name.cxx
index fe2955a..d1f3bd7 100644
--- a/build2/name.cxx
+++ b/build2/name.cxx
@@ -12,6 +12,9 @@
 
 namespace build2
 {
+  const name empty_name;
+  const names empty_names;
+
   string
   to_string (const name& n)
   {
diff --git a/build2/name.hxx b/build2/name.hxx
index 6f329ef..4394236 100644
--- a/build2/name.hxx
+++ b/build2/name.hxx
@@ -90,6 +90,8 @@ namespace build2
     compare (const name&) const;
   };
 
+  extern const name empty_name;
+
   inline bool
   operator== (const name& x, const name& y) {return x.compare (y) == 0;}
 
@@ -140,9 +142,10 @@ namespace build2
   // (names) and typed ones (vector<name>).
   //
   using names = small_vector<name, 1>;
-
   using names_view = vector_view<const name>;
 
+  extern const names empty_names;
+
   // The same semantics as to_stream(name).
   //
   ostream&
diff --git a/build2/operation.cxx b/build2/operation.cxx
index eb96559..d917f1e 100644
--- a/build2/operation.cxx
+++ b/build2/operation.cxx
@@ -4,6 +4,8 @@
 
 #include <build2/operation.hxx>
 
+#include <iostream> // cout
+
 #include <build2/file.hxx>
 #include <build2/dump.hxx>
 #include <build2/scope.hxx>
@@ -41,6 +43,25 @@ namespace build2
     return os;
   }
 
+  // noop
+  //
+  const meta_operation_info mo_noop {
+    noop_id,
+    "noop",
+    "",      // Presumably we will never need these since we are not going
+    "",      // to do anything.
+    "",
+    "",
+    nullptr, // meta-operation pre
+    nullptr, // operation pre
+    &load,
+    nullptr, // search
+    nullptr, // match
+    nullptr, // execute
+    nullptr, // operation post
+    nullptr  // meta-operation post
+  };
+
   // perform
   //
   void
@@ -395,43 +416,117 @@ namespace build2
     assert (dependency_count.load (memory_order_relaxed) == 0);
   }
 
-  const meta_operation_info noop {
-    noop_id,
-    "noop",
-    "",      // Presumably we will never need these since we are not going
-    "",      // to do anything.
+  const meta_operation_info mo_perform {
+    perform_id,
+    "perform",
+    "",
+    "",
     "",
     "",
     nullptr, // meta-operation pre
     nullptr, // operation pre
     &load,
-    nullptr, // search
-    nullptr, // match
-    nullptr, // execute
+    &search,
+    &match,
+    &execute,
     nullptr, // operation post
     nullptr  // meta-operation post
   };
 
-  const meta_operation_info perform {
-    perform_id,
-    "perform",
+  // info
+  //
+  static operation_id
+  info_operation_pre (const values&, operation_id o)
+  {
+    if (o != default_id)
+      fail << "explicit operation specified for meta-operation info";
+
+    return o;
+  }
+
+  void
+  info_load (const values&,
+             scope& rs,
+             const path&,
+             const dir_path& out_base,
+             const dir_path& src_base,
+             const location& l)
+  {
+    // For info we don't want to go any further than bootstrap so that it can
+    // be used in pretty much any situation (unresolved imports, etc). We do
+    // need to setup root as base though.
+
+    if (rs.out_path () != out_base || rs.src_path () != src_base)
+      fail (l) << "meta-operation info target must be project root directory";
+
+    setup_base (scopes.rw (rs).insert (out_base, false), out_base, src_base);
+  }
+
+  void
+  info_search (const values&,
+               const scope& rs,
+               const scope&,
+               const target_key& tk,
+               const location& l,
+               action_targets& ts)
+  {
+    // Collect all the projects we need to print information about.
+
+    // We've already verified the target is in the project root. Now verify
+    // it is dir{}.
+    //
+    if (!tk.type->is_a<dir> ())
+      fail (l) << "meta-operation info target must be project root directory";
+
+    ts.push_back (&rs);
+  }
+
+  static void
+  info_execute (const values&, action, action_targets& ts, bool)
+  {
+    for (size_t i (0); i != ts.size (); ++i)
+    {
+      // Separate projects with blank lines.
+      //
+      if (i != 0)
+        cout << endl;
+
+      const scope& s (*static_cast<const scope*> (ts[i]));
+
+      // This could be a simple project that doesn't set project name.
+      //
+      cout
+        << "project: "      << cast_empty<string> (s[var_project]) << endl
+        << "version: "      << cast_empty<string> (s[var_version]) << endl
+        << "summary: "      << cast_empty<string> (s[var_project_summary]) << endl
+        << "url: "          << cast_empty<string> (s[var_project_url]) << endl
+        << "src_root: "     << cast<dir_path> (s[var_src_root]) << endl
+        << "out_root: "     << cast<dir_path> (s[var_out_root]) << endl
+        << "amalgamation: " << cast_empty<dir_path> (s[var_amalgamation]) << endl
+        << "subprojects: "  << cast_empty<subprojects> (s[var_subprojects]) << endl;
+    }
+  }
+
+  const meta_operation_info mo_info {
+    info_id,
+    "info",
     "",
     "",
     "",
     "",
     nullptr, // meta-operation pre
-    nullptr, // operation pre
-    &load,
-    &search,
-    &match,
-    &execute,
+    &info_operation_pre,
+    &info_load,
+    &info_search,
+    nullptr, // match
+    &info_execute,
     nullptr, // operation post
     nullptr  // meta-operation post
   };
 
   // operations
   //
-  const operation_info default_ {
+  const operation_info op_default {
     default_id,
     "<default>",
     "",
@@ -444,7 +539,7 @@ namespace build2
     nullptr
   };
 
-  const operation_info update {
+  const operation_info op_update {
     update_id,
     "update",
     "update",
@@ -457,7 +552,7 @@ namespace build2
     nullptr
   };
 
-  const operation_info clean {
+  const operation_info op_clean {
     clean_id,
     "clean",
     "clean",
diff --git a/build2/operation.hxx b/build2/operation.hxx
index 24340dd..abd85c0 100644
--- a/build2/operation.hxx
+++ b/build2/operation.hxx
@@ -111,6 +111,7 @@ namespace build2
   const meta_operation_id disfigure_id = 4;
   const meta_operation_id create_id    = 5;
   const meta_operation_id dist_id      = 6;
+  const meta_operation_id info_id      = 7;
 
   // The default operation is a special marker that can be used to indicate
   // that no operation was explicitly specified by the user. If adding
@@ -279,8 +280,9 @@ namespace build2
   void
   execute (const values&, action, const action_targets&, bool quiet);
 
-  extern const meta_operation_info noop;
-  extern const meta_operation_info perform;
+  extern const meta_operation_info mo_noop;
+  extern const meta_operation_info mo_perform;
+  extern const meta_operation_info mo_info;
 
   // Operation info.
   //
@@ -323,9 +325,9 @@ namespace build2
 
   // Built-in operations.
   //
-  extern const operation_info default_;
-  extern const operation_info update;
-  extern const operation_info clean;
+  extern const operation_info op_default;
+  extern const operation_info op_update;
+  extern const operation_info op_clean;
 
   // Global meta/operation tables. Each registered meta/operation
   // is assigned an id which is used as an index in the per-project
diff --git a/build2/test/init.cxx b/build2/test/init.cxx
index 93ca1e4..1c7a2b4 100644
--- a/build2/test/init.cxx
+++ b/build2/test/init.cxx
@@ -31,7 +31,7 @@ namespace build2
 
       // Register the test operation.
       //
-      rs.operations.insert (test_id, test);
+      rs.operations.insert (test_id, op_test);
 
       // Enter module variables. Do it during boot in case they get assigned
       // in bootstrap.build.
diff --git a/build2/test/operation.cxx b/build2/test/operation.cxx
index 46b9366..e4591e4 100644
--- a/build2/test/operation.cxx
+++ b/build2/test/operation.cxx
@@ -22,7 +22,7 @@ namespace build2
       return mo != disfigure_id ? update_id : 0;
     }
 
-    const operation_info test {
+    const operation_info op_test {
       test_id,
       "test",
       "test",
diff --git a/build2/test/operation.hxx b/build2/test/operation.hxx
index d834edf..774e8d0 100644
--- a/build2/test/operation.hxx
+++ b/build2/test/operation.hxx
@@ -14,7 +14,7 @@ namespace build2
 {
   namespace test
   {
-    extern const operation_info test;
+    extern const operation_info op_test;
   }
 }
 
diff --git a/build2/variable.cxx b/build2/variable.cxx
index ed9527e..d8b48d0 100644
--- a/build2/variable.cxx
+++ b/build2/variable.cxx
@@ -406,6 +406,10 @@ namespace build2
     throw invalid_argument (m);
   }
 
+  // names
+  //
+  const names& value_traits<names>::empty_instance = empty_names;
+
   // bool value
   //
   bool value_traits<bool>::
diff --git a/build2/variable.hxx b/build2/variable.hxx
index bba2208..51cc350 100644
--- a/build2/variable.hxx
+++ b/build2/variable.hxx
@@ -546,6 +546,14 @@ namespace build2
   static int
   simple_compare (const value&, const value&);
 
+  // names
+  //
+  template <>
+  struct value_traits<names>
+  {
+    static const names& empty_instance;
+  };
+
   // bool
   //
   template <>
@@ -783,6 +791,8 @@ namespace build2
     static void prepend (value&, vector<T>&&);
     static bool empty (const vector<T>& x) {return x.empty ();}
 
+    static const vector<T> empty_instance;
+
     // Make sure these are static-initialized together. Failed that VC will
     // make sure it's done in the wrong order.
     //
@@ -809,6 +819,8 @@ namespace build2
       return append (v, move (x));}
     static bool empty (const map<K, V>& x) {return x.empty ();}
 
+    static const map<K, V> empty_instance;
+
     // Make sure these are static-initialized together. Failed that VC will
     // make sure it's done in the wrong order.
     //
diff --git a/build2/variable.txx b/build2/variable.txx
index e374f22..c2dbea9 100644
--- a/build2/variable.txx
+++ b/build2/variable.txx
@@ -389,6 +389,9 @@ namespace build2
   }
 
   template <typename T>
+  const vector<T> value_traits<vector<T>>::empty_instance;
+
+  template <typename T>
   const typename value_traits<vector<T>>::value_type_ex
   value_traits<vector<T>>::value_type = build2::value_type // VC14 wants =.
   {
@@ -558,6 +561,9 @@ namespace build2
   }
 
   template <typename K, typename V>
+  const std::map<K,V> value_traits<std::map<K, V>>::empty_instance;
+
+  template <typename K, typename V>
   const typename value_traits<std::map<K, V>>::value_type_ex
   value_traits<std::map<K, V>>::value_type = build2::value_type // VC14 wants =
   {