Implement base method of sync

This is useful for forcing progress when embedding Syndicate in
contexts that don't expose turn semantics.

lock.json

@@ -55,6 +55,23 @@
       "srcDir": "",
       "url": "https://github.com/ehmry/hashlib/archive/f9455d4be988e14e3dc7933eb7cc7d7c4820b7ac.tar.gz"
     },
+    {
+      "date": "2024-04-22T13:22:01+02:00",
+      "deepClone": false,
+      "fetchLFS": false,
+      "fetchSubmodules": true,
+      "hash": "sha256-ROpWQYIhgDRJAOJd1dAGkJCVxI2Tz8xoHYjLTQDfXaA=",
+      "leaveDotGit": false,
+      "method": "git",
+      "packages": [
+        "preserves"
+      ],
+      "path": "/nix/store/ichqy1plhjd6yql7y3dh540cshq07xv7-preserves-nim",
+      "rev": "fd498c6457cb9ad2f3179daa40da69eec00326dd",
+      "sha256": "182xvw04vjw83mlcrkwkip29b44h0v8dapg2014k9011h90mdsj4",
+      "srcDir": "src",
+      "url": "https://git.syndicate-lang.org/ehmry/preserves-nim.git"
+    },
     {
       "method": "fetchzip",
       "packages": [
@@ -77,17 +94,6 @@
       "srcDir": "src",
       "url": "https://github.com/zevv/npeg/archive/ec0cc6e64ea4c62d2aa382b176a4838474238f8d.tar.gz"
     },
-    {
-      "method": "fetchzip",
-      "packages": [
-        "preserves"
-      ],
-      "path": "/nix/store/2hy124xgabz134dxj3wji7mp47fdwy3w-source",
-      "rev": "9ae435a83c6d5028405538af5d24a023af625b6e",
-      "sha256": "1k7ywcp1a53x2fpc6wc2b0qzb264dkifash0s1wcp66rw3lx15k2",
-      "srcDir": "src",
-      "url": "https://git.syndicate-lang.org/ehmry/preserves-nim/archive/9ae435a83c6d5028405538af5d24a023af625b6e.tar.gz"
-    },
     {
       "method": "fetchzip",
       "packages": [

src/syndicate/actors.nim

@@ -147,7 +147,11 @@ when tracing:
 method publish*(e: Entity; turn: var Turn; v: AssertionRef; h: Handle) {.base.} = discard
 method retract*(e: Entity; turn: var Turn; h: Handle) {.base.} = discard
 method message*(e: Entity; turn: var Turn; v: AssertionRef) {.base.} = discard
-method sync*(e: Entity; turn: var Turn; peer: Cap) {.base.} = discard
+
+proc message*(turn: var Turn; r: Cap; v: Value)
+
+method sync*(e: Entity; turn: var Turn; peer: Cap) {.base.} =
+  message(turn, peer, true.toPreserves)
 
 converter toActor(f: Facet): Actor = f.actor
 converter toActor(t: Turn): Actor = t.facet.actor
@@ -736,8 +740,24 @@ proc runPendingTurns* =
       terminateActor(turn, err)
       raise err
 
+proc runOnce*: bool {.discardable.} =
+  ## Run pending turns if there are any, otherwise
+  ## poll for external events and run any resulting turns.
+  ## Return true if any turns have been processed.
+  if turnQueue.len == 0:
+    when defined(solo5):
+      discard solo5_dispatcher.runOnce()
+    else:
+      var ready: seq[Continuation]
+      ioqueue.poll(ready)
+      while ready.len > 0:
+        discard trampoline:
+          ready.pop()
+  result = turnQueue.len > 0
+  runPendingTurns()
+
 proc run* =
-  ## Run actors to completion
+  ## Run actors to completion.
   when defined(solo5):
     while turnQueue.len > 0 or solo5_dispatcher.runOnce():
       runPendingTurns()

syndicate.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version = "20240421"
+version = "20240424"
 author        = "Emery Hemingway"
 description   = "Syndicated actors for conversational concurrency"
 license       = "Unlicense"
@@ -9,4 +9,4 @@ srcDir        = "src"
 
 # Dependencies
 
-requires "https://github.com/ehmry/hashlib.git >= 20231130", "nim >= 2.0.0", "https://git.syndicate-lang.org/ehmry/preserves-nim.git >= 20240312", "https://github.com/ehmry/nim-sys.git#4ef3b624db86e331ba334e705c1aa235d55b05e1", "https://git.sr.ht/~ehmry/nim_taps >= 20240405"
+requires "https://github.com/ehmry/hashlib.git >= 20231130", "nim >= 2.0.0", "https://git.syndicate-lang.org/ehmry/preserves-nim.git >= 20240422", "https://github.com/ehmry/nim-sys.git#4ef3b624db86e331ba334e705c1aa235d55b05e1", "https://git.sr.ht/~ehmry/nim_taps >= 20240405"