document file: undo the clean stop's mark before deciding the actor

At start, a node on a document file appends an Opened record before it
writes anything, so that a Closed record before it no longer says the
file holds every change of the actor it names. It does so now before
deciding which actor to write as, and DocumentFile::open says whether it
could: where the append fails (the disk full, permissions), the file
still ends with Closed, and later appends likely fail too. A crash, or a
clean stop whose last append failed (close then sees the file behind and
writes no mark), would leave that Closed standing for a run the file
never got. So with --keep-actor, the node writes on as the actor of
before only where the file was marked as opened; else it writes as a
fresh actor and warns.

1 files changed, 13 insertions, 7 deletions

diff --git a/src/document/file.rs b/src/document/file.rs
index 56114f5..1a33918 100644
--- a/src/document/file.rs
+++ b/src/document/file.rs
@@ -399,16 +399,22 @@ impl DocumentFile {
 
     /// Marks the file as opened (`Record::Opened`), at start, before the node writes:
     /// a `Closed` before it no longer says the file holds everything (a crash from here
-    /// on leaves it without one). Nothing where there is no file yet.
-    pub(crate) fn open(&self) {
+    /// on leaves it without one). Nothing where there is no file yet. Whether the file
+    /// now ends without a `Closed`: where the mark couldn't be appended, it still says
+    /// the run of before stopped cleanly, and the node must not write on as its actor.
+    pub(crate) fn open(&self) -> bool {
         if !self.path.exists() {
-            return;
+            return true;
         }
-        if let Err(error) =
-            self.files
-                .append(FileKind::Document, &self.path, &record(Record::Opened, &[]))
+        match self
+            .files
+            .append(FileKind::Document, &self.path, &record(Record::Opened, &[]))
         {
-            error!(path = %self.path.display(), error = %error, "Couldn't mark the document file as opened");
+            Ok(()) => true,
+            Err(error) => {
+                error!(path = %self.path.display(), error = %error, "Couldn't mark the document file as opened");
+                false
+            }
         }
     }