Add support for pair representation reversibility

6 files changed, 100 insertions, 46 deletions

diff --git a/build2/name b/build2/name
index 99c21f4..a4de95c 100644
--- a/build2/name
+++ b/build2/name
@@ -68,19 +68,24 @@ namespace build2
     bool
     empty () const {return dir.empty () && value.empty ();}
 
-    // Note that strictly speaking the following tests should be
-    // orthogonal to qualification. However, the vast majority of
-    // cases where we expect a simple or directory name, we also
-    // expect it to be unqualified.
+    // Note that strictly speaking the following tests should be orthogonal
+    // to qualification. However, the vast majority of cases where we expect
+    // a simple or directory name, we also expect it to be unqualified.
     //
     // Note also that empty name is simple but not a directory.
     //
     bool
-    simple () const {return unqualified () && untyped () && dir.empty ();}
+    simple (bool ignore_qual = false) const
+    {
+      return (ignore_qual || unqualified ()) && untyped () && dir.empty ();
+    }
 
     bool
-    directory () const
-    {return unqualified () && untyped () && !dir.empty () && value.empty ();}
+    directory (bool ignore_qual = false) const
+    {
+      return (ignore_qual || unqualified ()) &&
+        untyped () && !dir.empty () && value.empty ();
+    }
 
     const std::string* proj = nullptr; // Points to project_name_pool.
     dir_path dir;
diff --git a/build2/parser.cxx b/build2/parser.cxx
index e1d63aa..ab9012c 100644
--- a/build2/parser.cxx
+++ b/build2/parser.cxx
@@ -1064,7 +1064,7 @@ namespace build2
 
           // Should evaluate to true or false.
           //
-          if (ns.size () != 1 || !value_traits<bool>::assign (ns[0]))
+          if (ns.size () != 1 || !assign<bool> (ns[0]))
             fail (nsl) << "expected " << k << "-expression to evaluate to "
                        << "'true' or 'false' instead of '" << ns << "'";
 
diff --git a/build2/variable b/build2/variable
index a2490ac..029aafa 100644
--- a/build2/variable
+++ b/build2/variable
@@ -214,10 +214,15 @@ namespace build2
   template <typename T> typename value_traits<T>::const_type as (const value&);
 
   // Try to "assign" a simple value type to the value stored in name. Return
-  // false if the value is not valid for this type.
+  // false if the value is not valid for this type. The second version is
+  // called for a pair and it is expected to merge the result into the first
+  // name.
   //
   template <typename T> bool assign (name&);
+  template <typename T> bool assign (name&, name&);
 
+  // Name cast. Can only be called after assign() above returned true.
+  //
   template <typename T> typename value_traits<T>::type as (name&);
   template <typename T> typename value_traits<T>::const_type as (const name&);
 
@@ -270,7 +275,7 @@ namespace build2
     static type       as (value&);
     static const_type as (const value&);
 
-    static bool assign (name&);
+    static bool assign (name&, name*);
     static void assign (value&, bool);
     static void append (value&, bool);
 
@@ -293,7 +298,7 @@ namespace build2
     static type       as (value&);
     static const_type as (const value&);
 
-    static bool assign (name&);
+    static bool assign (name&, name*);
     static void assign (value&, string);
     static void append (value&, string);
 
@@ -316,7 +321,7 @@ namespace build2
     static type       as (value&);
     static const_type as (const value&);
 
-    static bool assign (name&);
+    static bool assign (name&, name*);
     static void assign (value&, dir_path);
     static void append (value&, dir_path);
 
@@ -339,7 +344,7 @@ namespace build2
     static type       as (value&);
     static const_type as (const value&);
 
-    static bool assign (name&) {return true;}
+    static bool assign (name&, name* r) {return r == nullptr;}
     static void assign (value&, name);
     static void append (value&, name) = delete;
 
diff --git a/build2/variable.cxx b/build2/variable.cxx
index 39d8cdd..ce06d3e 100644
--- a/build2/variable.cxx
+++ b/build2/variable.cxx
@@ -123,9 +123,9 @@ namespace build2
   // bool value
   //
   bool value_traits<bool>::
-  assign (name& n)
+  assign (name& n, name* r)
   {
-    if (n.simple ())
+    if (r == nullptr && n.simple ())
     {
       const string& s (n.value);
 
@@ -145,7 +145,7 @@ namespace build2
     {
       name& n (v.front ());
 
-      if (value_traits<bool>::assign (n))
+      if (assign<bool> (n))
         return true;
     }
 
@@ -178,47 +178,64 @@ namespace build2
   // string value
   //
   bool value_traits<string>::
-  assign (name& n)
+  assign (name& n, name* r)
   {
-    // The below code is quite convoluted because we don't want to
-    // modify the name until we know it good (if it is not, then it
-    // will most likely be printed by the caller in diagnostics).
-
-    // Suspend project qualification.
+    // The goal is to reverse the name into its original representation. The
+    // code is a bit convoluted because we try to avoid extra allocation for
+    // the common cases (unqualified, unpaired simple name or directory).
     //
-    const string* p (n.proj);
-    n.proj = nullptr;
 
-    // Convert directory to string.
+    // We can only convert project-qualified simple and directory names.
     //
-    if (n.directory ())
+    if (!(n.simple (true) || n.directory (true)) ||
+        !(r == nullptr || r->simple (true) || r->directory (true)))
+      return false;
+
+    if (n.directory (true))
     {
       n.value = move (n.dir).string (); // Move string out of path.
 
-      // Add / back to the end of the path unless it is already there.
-      // Note that the string cannot be empty (n.directory () would
-      // have been false).
+      // Add / back to the end of the path unless it is already there. Note
+      // that the string cannot be empty (n.directory () would have been
+      // false).
       //
       if (!dir_path::traits::is_separator (n.value[n.value.size () - 1]))
         n.value += '/';
     }
 
-    if (!n.simple ())
-    {
-      n.proj = p; // Restore.
-      return false;
-    }
-
     // Convert project qualification to its string representation.
     //
-    if (p != nullptr)
+    if (n.qualified ())
     {
-      string s (*p);
+      string s (*n.proj);
       s += '%';
       s += n.value;
       s.swap (n.value);
     }
 
+    // The same for the RHS of a pair, if we have one.
+    //
+    if (r != nullptr)
+    {
+      n.value += '@';
+
+      if (r->qualified ())
+      {
+        n.value += *r->proj;
+        n.value += '%';
+      }
+
+      if (r->directory (true))
+      {
+        n.value += r->dir.string ();
+
+        if (!dir_path::traits::is_separator (n.value[n.value.size () - 1]))
+          n.value += '/';
+      }
+      else
+        n.value += r->value;
+    }
+
     return true;
   }
 
@@ -236,7 +253,7 @@ namespace build2
     {
       name& n (v.front ());
 
-      if (value_traits<string>::assign (n))
+      if (assign<string> (n))
         return !n.value.empty ();
     }
 
@@ -271,8 +288,11 @@ namespace build2
   // dir_path value
   //
   bool value_traits<dir_path>::
-  assign (name& n)
+  assign (name& n, name* r)
   {
+    if (r != nullptr)
+      return false;
+
     if (n.directory ())
       return true;
 
@@ -304,7 +324,7 @@ namespace build2
     {
       name& n (v.front ());
 
-      if (value_traits<dir_path>::assign (n))
+      if (assign<dir_path> (n))
         return !n.dir.empty ();
     }
 
diff --git a/build2/variable.ixx b/build2/variable.ixx
index b368c6e..df3f0c5 100644
--- a/build2/variable.ixx
+++ b/build2/variable.ixx
@@ -34,7 +34,14 @@ namespace build2
   inline bool
   assign (name& n)
   {
-    return value_traits<T>::assign (n);
+    return value_traits<T>::assign (n, nullptr);
+  }
+
+  template <typename T>
+  inline bool
+  assign (name& l, name& r)
+  {
+    return value_traits<T>::assign (l, &r);
   }
 
   template <typename T>
diff --git a/build2/variable.txx b/build2/variable.txx
index 54e48a3..7a0d53a 100644
--- a/build2/variable.txx
+++ b/build2/variable.txx
@@ -12,13 +12,30 @@ namespace build2
   bool
   vector_assign (names& v, const variable& var)
   {
-    // Verify each element has valid value of T.
+    // Verify each element has valid value of T. Merge pairs.
     //
-    for (name& n: v)
+    for (auto i (v.begin ()); i != v.end (); )
     {
-      if (!assign<T> (n))
-        fail << "invalid " << value_traits<T>::value_type.name << " element "
-             << "'" << n << "' in variable '" << var.name << "'";
+      name& n (*i);
+
+      if (n.pair)
+      {
+        name& r (*++i);
+
+        if (!assign<T> (n, r))
+          fail << "invalid " << value_traits<T>::value_type.name
+               << " pair '" << n << "'@'" << r << "'"
+               << " in variable '" << var.name << "'";
+
+        i = v.erase (i);
+      }
+      else
+      {
+        if (!assign<T> (n))
+          fail << "invalid " << value_traits<T>::value_type.name
+               << " element '" << n << "' in variable '" << var.name << "'";
+        ++i;
+      }
     }
 
     return !v.empty ();