Add support for unnamed projects

Sometimes (e.g., in bpkg configuration) we don't have a project name.
In fact, it is not really a project; it can never be referenced in an
import directive.

So we now have a notion of an unnamed project. Such a project should
still have the 'project' variable set first thing in bootstrap.build
but its value should be empty.

Note that we can still amalgamate such projects just liked named ones.

8 files changed, 34 insertions, 5 deletions

diff --git a/build/file.cxx b/build/file.cxx
index f6fdd10..8f51660 100644
--- a/build/file.cxx
+++ b/build/file.cxx
@@ -338,7 +338,7 @@ namespace build
       name = move (as<string> (v));
     }
 
-    level5 ([&]{trace << "extracted project name " << name << " for "
+    level5 ([&]{trace << "extracted project name '" << name << "' for "
                       << *src_root;});
     return name;
   }
@@ -379,6 +379,15 @@ namespace build
       //
       string name (find_project_name (sd, dir_path (), &src));
 
+      // If the name is empty, then is is an unnamed project. While the
+      // '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.
+      //
+      if (name.empty ())
+        name = dir.posix_string () + '/';
+
       // @@ Can't use move() because we may need the values in diagnostics
       // below. Looks like C++17 try_emplace() is what we need.
       //
@@ -571,9 +580,14 @@ namespace build
               // was specified by the user so it is most likely in our
               // src.
               //
-              i = v.data_.emplace (
-                i,
-                find_project_name (out_root / d, src_root / d));
+              string n (find_project_name (out_root / d, src_root / d));
+
+              // See find_subprojects() for details on unnamed projects.
+              //
+              if (n.empty ())
+                n = d.posix_string () + '/';
+
+              i = v.data_.emplace (i, move (n));
 
               i->pair = '=';
               ++i;
diff --git a/build/name.cxx b/build/name.cxx
index 4061c78..1bb8d31 100644
--- a/build/name.cxx
+++ b/build/name.cxx
@@ -53,7 +53,7 @@ namespace build
       os << n;
 
       if (n.pair != '\0')
-        os <<  n.pair;
+        os << n.pair;
       else if (i != e)
         os << ' ';
     }
diff --git a/tests/amalgam/unnamed/build/bootstrap.build b/tests/amalgam/unnamed/build/bootstrap.build
new file mode 100644
index 0000000..30065f4
--- /dev/null
+++ b/tests/amalgam/unnamed/build/bootstrap.build
@@ -0,0 +1,3 @@
+project = amalgam-unnamed
+amalgamation = # Disabled.
+using config
diff --git a/tests/amalgam/unnamed/buildfile b/tests/amalgam/unnamed/buildfile
new file mode 100644
index 0000000..5aa12c3
--- /dev/null
+++ b/tests/amalgam/unnamed/buildfile
@@ -0,0 +1,3 @@
+.: sub/
+include sub/
+print $subprojects
diff --git a/tests/amalgam/unnamed/sub/build/bootstrap.build b/tests/amalgam/unnamed/sub/build/bootstrap.build
new file mode 100644
index 0000000..ce3735a
--- /dev/null
+++ b/tests/amalgam/unnamed/sub/build/bootstrap.build
@@ -0,0 +1,2 @@
+project =
+using config
diff --git a/tests/amalgam/unnamed/sub/buildfile b/tests/amalgam/unnamed/sub/buildfile
new file mode 100644
index 0000000..8717375
--- /dev/null
+++ b/tests/amalgam/unnamed/sub/buildfile
@@ -0,0 +1,2 @@
+./:
+print "'$project'"
diff --git a/tests/amalgam/unnamed/test.out b/tests/amalgam/unnamed/test.out
new file mode 100644
index 0000000..1738349
--- /dev/null
+++ b/tests/amalgam/unnamed/test.out
@@ -0,0 +1,2 @@
+''
+sub/=sub/
diff --git a/tests/amalgam/unnamed/test.sh b/tests/amalgam/unnamed/test.sh
new file mode 100755
index 0000000..b898b3c
--- /dev/null
+++ b/tests/amalgam/unnamed/test.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+valgrind -q b -q | diff -u test.out -