# HG changeset patch
# User Raphaël Gomès <rgomes@octobus.net>
# Date 2021-04-19 09:22:21
# Node ID 81eb7091c494831b0f3701034cd70eef865a10b7
# Parent  1680c94741f821399c4117d113b68f80db090c01

sidedata: add a way of replacing an existing sidedata computer

This will be useful in a future patch to replace a sequential computer with
a parallel computer. We only allow for explicit replacement, to force the users
to think about overriding computers.

Differential Revision: https://phab.mercurial-scm.org/D10358

diff --git a/mercurial/interfaces/repository.py b/mercurial/interfaces/repository.py
--- a/mercurial/interfaces/repository.py
+++ b/mercurial/interfaces/repository.py
@@ -1856,7 +1856,9 @@ class ilocalrepositorymain(interfaceutil
     def savecommitmessage(text):
         pass
 
-    def register_sidedata_computer(kind, category, keys, computer, flags):
+    def register_sidedata_computer(
+        kind, category, keys, computer, flags, replace=False
+    ):
         pass
 
     def register_wanted_sidedata(category):
diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -3370,16 +3370,25 @@ class localrepository(object):
             return
         self._wanted_sidedata.add(pycompat.bytestr(category))
 
-    def register_sidedata_computer(self, kind, category, keys, computer, flags):
+    def register_sidedata_computer(
+        self, kind, category, keys, computer, flags, replace=False
+    ):
         if kind not in revlogconst.ALL_KINDS:
             msg = _(b"unexpected revlog kind '%s'.")
             raise error.ProgrammingError(msg % kind)
         category = pycompat.bytestr(category)
-        if category in self._sidedata_computers.get(kind, []):
+        already_registered = category in self._sidedata_computers.get(kind, [])
+        if already_registered and not replace:
             msg = _(
                 b"cannot register a sidedata computer twice for category '%s'."
             )
             raise error.ProgrammingError(msg % category)
+        if replace and not already_registered:
+            msg = _(
+                b"cannot replace a sidedata computer that isn't registered "
+                b"for category '%s'."
+            )
+            raise error.ProgrammingError(msg % category)
         self._sidedata_computers.setdefault(kind, {})
         self._sidedata_computers[kind][category] = (keys, computer, flags)