Print 'Waiting for another process to install x, y, z' in distributed builds (#28535)

Co-authored-by: Massimiliano Culpo <massimiliano.culpo@gmail.com>

lib/spack/spack/installer.py

@@ -648,6 +648,49 @@ def set(self, text):
         sys.stdout.flush()
 
 
+class TermStatusLine(object):
+    """
+    This class is used in distributed builds to inform the user that other packages are
+    being installed by another process.
+    """
+    def __init__(self, enabled):
+        self.enabled = enabled
+        self.pkg_set = set()
+        self.pkg_list = []
+
+    def add(self, pkg_id):
+        """
+        Add a package to the waiting list, and if it is new, update the status line.
+        """
+        if not self.enabled or pkg_id in self.pkg_set:
+            return
+
+        self.pkg_set.add(pkg_id)
+        self.pkg_list.append(pkg_id)
+        tty.msg(colorize('@*{Waiting for} @*g{%s}' % pkg_id))
+        sys.stdout.flush()
+
+    def clear(self):
+        """
+        Clear the status line.
+        """
+        if not self.enabled:
+            return
+
+        lines = len(self.pkg_list)
+
+        if lines == 0:
+            return
+
+        self.pkg_set.clear()
+        self.pkg_list.clear()
+
+        # Move the cursor to the beginning of the first "Waiting for" message and clear
+        # everything after it.
+        sys.stdout.write('\x1b[%sF\x1b[J' % lines)
+        sys.stdout.flush()
+
+
 class PackageInstaller(object):
     '''
     Class for managing the install process for a Spack instance based on a
@@ -1500,6 +1543,10 @@ def install(self):
 
         term_title = TermTitle(len(self.build_pq))
 
+        # Only enable the terminal status line when we're in a tty without debug info
+        # enabled, so that the output does not get cluttered.
+        term_status = TermStatusLine(enabled=sys.stdout.isatty() and not tty.is_debug())
+
         while self.build_pq:
             term_title.next_pkg()
 
@@ -1523,6 +1570,7 @@ def install(self):
             # all subsequent tasks will have non-zero priorities or may be
             # dependencies of this task.
             if task.priority != 0:
+                term_status.clear()
                 tty.error('Detected uninstalled dependencies for {0}: {1}'
                           .format(pkg_id, task.uninstalled_deps))
                 left = [dep_id for dep_id in task.uninstalled_deps if
@@ -1545,12 +1593,14 @@ def install(self):
             # some package likely depends on it.
             if not task.explicit:
                 if _handle_external_and_upstream(pkg, False):
+                    term_status.clear()
                     self._flag_installed(pkg, task.dependents)
                     continue
 
             # Flag a failed spec.  Do not need an (install) prefix lock since
             # assume using a separate (failed) prefix lock file.
             if pkg_id in self.failed or spack.store.db.prefix_failed(spec):
+                term_status.clear()
                 tty.warn('{0} failed to install'.format(pkg_id))
                 self._update_failed(task)
 
@@ -1569,6 +1619,7 @@ def install(self):
             # determined the spec has already been installed (though the
             # other process may be hung).
             term_title.set('Acquiring lock for {0}'.format(pkg.name))
+            term_status.add(pkg_id)
             ltype, lock = self._ensure_locked('write', pkg)
             if lock is None:
                 # Attempt to get a read lock instead.  If this fails then
@@ -1583,6 +1634,8 @@ def install(self):
                 self._requeue_task(task)
                 continue
 
+            term_status.clear()
+
             # Take a timestamp with the overwrite argument to allow checking
             # whether another process has already overridden the package.
             if task.request.overwrite and task.explicit: