dirstate-map: add a missing debug wait point when accessing the v2 docket

dirstate-map: add a missing debug wait point when accessing the v2 docket

fc8e37c380d3 added synchronization points to the dirstate to allow for race
condition testing without actually requiring a time-based race condition
to happen.

This changes adds the `pre-read-file` wait point before we read the docket,
since callers might ask for the parents before anything else is
read, leading to the first read being done before the wait point.

This removes some differences in test output which were presumed to be
speed related, but weren't.

--- a/mercurial/dirstatemap.py	Thu Oct 03 00:31:25 2024 +0200
+++ b/mercurial/dirstatemap.py	Mon Oct 14 14:14:21 2024 +0200
@@ -167,6 +167,7 @@
         return fp
 
     def _readdirstatefile(self, size: int = -1) -> bytes:
+        testing.wait_on_cfg(self._ui, b'dirstate.pre-read-file')
         try:
             with self._opendirstatefile() as fp:
                 return fp.read(size)
@@ -176,6 +177,7 @@
 
     @property
     def docket(self) -> "docketmod.DirstateDocket":
+        testing.wait_on_cfg(self._ui, b'dirstate.pre-read-file')
         if not self._docket:
             if not self._use_dirstate_v2:
                 raise error.ProgrammingError(

--- a/tests/test-dirstate-read-race.t	Thu Oct 03 00:31:25 2024 +0200
+++ b/tests/test-dirstate-read-race.t	Mon Oct 14 14:14:21 2024 +0200
@@ -167,23 +167,7 @@
 
 The status process should return a consistent result and not crash.
 
-#if dirstate-v1
-  $ cat $TESTTMP/status-race-lock.out
-  A dir/n
-  A dir/o
-  R dir/nested/m
-  ? p
-  ? q
-#else
-#if rhg pre-some-read dirstate-v2-append
-  $ cat $TESTTMP/status-race-lock.out
-  A dir/o
-  R dir/nested/m
-  ? dir/n
-  ? p
-  ? q
-#else
-#if rust no-rhg dirstate-v2-append
+#if rust dirstate-v2-append pre-some-read
   $ cat $TESTTMP/status-race-lock.out
   A dir/o
   R dir/nested/m
@@ -198,8 +182,6 @@
   ? p
   ? q
 #endif
-#endif
-#endif
   $ cat $TESTTMP/status-race-lock.log
 
 final cleanup
@@ -249,30 +231,19 @@
 
 The status process should return a consistent result and not crash.
 
-#if no-rhg
+#if dirstate-v1
+  $ cat $TESTTMP/status-race-lock.out
+  ? dir/n
+  ? p
+  ? q
+#endif
+#if dirstate-v2
   $ cat $TESTTMP/status-race-lock.out
   A dir/o
   R dir/nested/m
   ? dir/n
   ? p
   ? q
-  $ cat $TESTTMP/status-race-lock.log
-#else
-#if pre-some-read dirstate-v2-append
-  $ cat $TESTTMP/status-race-lock.out
-  A dir/o
-  R dir/nested/m
-  ? dir/n
-  ? p
-  ? q
-  $ cat $TESTTMP/status-race-lock.log
-#else
-  $ cat $TESTTMP/status-race-lock.out
-  ? dir/n
-  ? p
-  ? q
-  $ cat $TESTTMP/status-race-lock.log
-#endif
 #endif
 
 final cleanup
@@ -323,21 +294,7 @@
 
 The status process should return a consistent result and not crash.
 
-#if rhg dirstate-v2-append pre-some-read
-  $ cat $TESTTMP/status-race-lock.out
-  A dir/o
-  R dir/nested/m
-  ! dir/i
-  ! dir/j
-  ! dir/nested/h
-  ! dir2/k
-  ! dir2/l
-  ! g
-  ? dir/n
-  ? p
-  ? q
-#else
-#if rust no-rhg dirstate-v2-append
+#if rust dirstate-v2-append pre-some-read
   $ cat $TESTTMP/status-race-lock.out
   A dir/o
   R dir/nested/m
@@ -357,7 +314,6 @@
   ? p
   ? q
 #endif
-#endif
   $ cat $TESTTMP/status-race-lock.log
 
 final cleanup