hook: make "mercurial" module available for Python hooks

Summary:
Some hooks (ex. mergedriver) are checked in old release branches. Provide
"mercurial" module compatibility so they won't break.

Reviewed By: mitrandir77

Differential Revision: D14366343

fbshipit-source-id: d47cc4fd512f63e4f6cdc5d7e5ab2c4398216b2f

edenscm/mercurial/extensions.py

@@ -291,7 +291,10 @@ def load(ui, name, path):
 
     # "mercurial" and "hgext" were moved. Detect wrong module imports.
     if ui.configbool("devel", "all-warnings"):
-        if "mercurial" in sys.modules or "hgext" in sys.modules:
+        if (
+            "mercurial" in sys.modules
+            and sys.modules["mercurial"] is not sys.modules["edenscm.mercurial"]
+        ) or "hgext" in sys.modules:
             ui.develwarn("extension %s imported incorrect modules" % name)
 
     # Before we do anything with the extension, check against minimum stated

edenscm/mercurial/hook.py

@@ -259,7 +259,8 @@ def runhooks(ui, repo, htype, hooks, throw=False, **args):
                     if repo:
                         path = os.path.join(repo.root, path)
                     try:
-                        mod = extensions.loadpath(path, "hghook.%s" % hname)
+                        with util.mercurialmodule():
+                            mod = extensions.loadpath(path, "hghook.%s" % hname)
                     except Exception as e:
                         ui.write(_("loading %s hook failed: %s\n") % (hname, e))
                         raise
@@ -270,7 +271,8 @@ def runhooks(ui, repo, htype, hooks, throw=False, **args):
                     # automatically.
                     if hookfn.startswith("hgext."):
                         hookfn = "edenscm." + hookfn
-                r, raised = _pythonhook(ui, repo, htype, hname, hookfn, args, throw)
+                with util.mercurialmodule():
+                    r, raised = _pythonhook(ui, repo, htype, hname, hookfn, args, throw)
             else:
                 r = _exthook(ui, repo, htype, hname, cmd, args, throw)
                 raised = False

edenscm/mercurial/util.py

@@ -793,6 +793,25 @@ def environoverride(name, value):
             encoding.environ[name] = origvalue
 
 
+class mercurialmodule(object):
+    """Provide 'mercurial' module compatibility. Used by legacy Python hooks."""
+
+    def __init__(self):
+        self._needdel = False
+
+    def __enter__(self):
+        if sys.modules.get("mercurial") is not sys.modules["edenscm.mercurial"]:
+            assert "mercurial" not in sys.modules
+            sys.modules["mercurial"] = sys.modules["edenscm.mercurial"]
+            self._needdel = True
+        return self
+
+    def __exit__(self, exctype, excvalue, traceback):
+        if self._needdel:
+            del sys.modules["mercurial"]
+            self._needdel = False
+
+
 class _lrucachenode(object):
     """A node in a doubly linked list.
 

tests/test-mergedriver2.t

@@ -20,8 +20,14 @@ and add B_add and C_add. Note: there are no conflicts.
   $ setconfig experimental.mergedriver=python:$TESTTMP/mergedriver-test.py
 
   $ cat > $TESTTMP/mergedriver-test.py << EOF
+  > from edenscm.mercurial import node
+  > from mercurial import node as node2
+  > assert node is node2
   > import os
   > def preprocess(ui, repo, hooktype, mergestate, wctx, labels):
+  >     from edenscm.mercurial import util
+  >     from mercurial import util as util2
+  >     assert util is util2
   >     ui.write("merge driver preprocess\n")
   >     # Right now, need to mark at least one file to get mergedriver running
   >     mergestate.mark("A", "d")  # driver-resovled