diff --git a/src/python/jw/pkg/App.py b/src/python/jw/pkg/App.py
index 8ee0f687..dabb97ef 100644
--- a/src/python/jw/pkg/App.py
+++ b/src/python/jw/pkg/App.py
@@ -198,7 +198,28 @@ class App(Base):
         except FileNotFoundError:
             return None
 
-    def __get_project_refs(
+    def read_dep_edges(
+        self,
+        name: str,
+        sections: list[str],
+        key: str,
+    ) -> list[str]:
+        """The deduplicated dependency values of name for the given
+        sections and key (flavour), in section and value order.
+        """
+        ret: list[str] = []
+        for section in sections:
+            vals = self.get_value(name, section, key)
+            log(DEBUG, f'name={name}, section={section}, key={key}, deps={vals}')
+            if not vals:
+                continue
+            for val in vals.split(','):
+                val = val.strip()
+                if (len(val)) and (val not in ret):
+                    ret.append(val)
+        return ret
+
+    def walk_project_deps(
         self,
         buf: list[str],
         visited: set[str],
@@ -208,7 +229,21 @@ class App(Base):
         add_self: bool,
         scope: Scope,
         names_only: bool,
+        *,
+        check_installed: bool = True,
+        exclude: set[str] = set(),
+        recurse: bool = True,
     ) -> None:
+        """Walk the dependency edges of sections and key (flavour)
+        starting at spec, appending the visited specs to buf in
+        postorder; buf and visited are updated in place.
+
+        check_installed applies the installed-package check, which
+        skips the dependencies of an installed run package and fails
+        on an unmet dependency. exclude names specs that are neither
+        traversed nor appended. recurse = False stops the walk at the
+        starting spec.
+        """
         dep = Dependency(spec)
         name = dep.base_name
         mod = dep.full_name
@@ -216,52 +251,44 @@ class App(Base):
             spec = name
         if spec in buf:
             return
+        if spec in exclude:
+            return
         if spec in visited:
             if add_self:
                 buf.append(spec)
             return
         visited.add(spec)
-        needed_subpackage = 'devel' if mod.endswith(('-dev', '-devel')) else 'run'
-        if not self.is_installed(name, devel = True):
-            if not mod.endswith(('-dev', '-devel')):
-                if self.is_installed(name, devel = False):
-                    return
-            raise Exception(
-                f'Unmet dependency on {mod}: the -{needed_subpackage} package '
-                f'of project {name} is not installed'
-            )
-        vals_list: list[str] = []
-        for section in sections:
-            vals = self.get_value(name, section, key)
-            log(
-                DEBUG,
-                (
-                    f'name={name}, section={section}, key={key}, deps={vals}, '
-                    f'scope={scope.name}, visited={visited}'
-                ),
-            )
-            if not vals:
-                continue
-            for val in vals.split(','):
-                val = val.strip()
-                if (len(val)) and (val not in vals_list):
-                    vals_list.append(val)
+        if check_installed:
+            needed_subpackage = 'devel' if mod.endswith(('-dev', '-devel')) else 'run'
+            if not self.is_installed(name, devel = True):
+                if not mod.endswith(('-dev', '-devel')):
+                    if self.is_installed(name, devel = False):
+                        return
+                raise Exception(
+                    f'Unmet dependency on {mod}: the -{needed_subpackage} package '
+                    f'of project {name} is not installed'
+                )
+        vals_list = self.read_dep_edges(name, sections, key)
         match scope:
             case Scope.Self:
                 buf += vals_list
             case Scope.One | Scope.Subtree:
-                subscope = scope.Self if scope == Scope.One else scope
-                for val in vals_list:
-                    self.__get_project_refs(
-                        buf,
-                        visited,
-                        val,
-                        sections,
-                        key,
-                        add_self = True,
-                        scope = subscope,
-                        names_only = names_only,
-                    )
+                if recurse:
+                    subscope = scope.Self if scope == Scope.One else scope
+                    for val in vals_list:
+                        self.walk_project_deps(
+                            buf,
+                            visited,
+                            val,
+                            sections,
+                            key,
+                            add_self = True,
+                            scope = subscope,
+                            names_only = names_only,
+                            check_installed = check_installed,
+                            exclude = exclude,
+                            recurse = recurse,
+                        )
         if add_self:
             buf.append(spec)
 
@@ -567,7 +594,7 @@ class App(Base):
             visited: set[str] = set()
             for name in projects:
                 rr: list[str] = []
-                self.__get_project_refs(
+                self.walk_project_deps(
                     rr, visited, name, sections, key, add_self, scope, names_only
                 )
                 # TODO: this looks like a performance hogger