msg: add assertion mode

README.md

@@ -313,6 +313,16 @@ $tuplespace ? [?id ?name] [
 ]
 ```
 
+## syndump
+
+Utility for printing assertions and messages. Parses the command-line arguments as a pattern, connects a dataspace via `$SYNDICATE_ROUTE`, and writes observations to standard-output. Published assertions are prefixed by the `+` character, retractions by `-`, and messages by `!`.
+
+Example
+```sh
+# Print patterns in use, filter down with AWK to only the published patterns.
+$ FS=':' syndump '<Observe ? _>' | awk -F : '/^+/ { print $2 }'
+```
+
 ## XSLT processor
 
 Perform XML stylesheet transformations. For a given textual XSLT stylesheet and a textual XML document generate an abstract XML document in Preserves form. Inputs may be XML text or paths to XML files.

src/syndump.nim

@@ -0,0 +1,69 @@
+# SPDX-FileCopyrightText: ☭ Emery Hemingway
+# SPDX-License-Identifier: Unlicense
+
+import std/[os, tables]
+import preserves, syndicate, syndicate/[durings, relays]
+
+proc parsePattern(pr: Value): Pattern =
+  let
+    dropSigil = initRecord("lit", "_".toSymbol)
+    grabSigil = initRecord("lit", "?".toSymbol)
+  var pr = grab(pr).toPreserves
+  apply(pr) do (pr: var Value):
+    if pr == dropSigil:
+      pr = initRecord("_")
+    elif pr == grabSigil:
+      pr = initRecord("bind", initRecord("_"))
+  doAssert result.fromPreserves(pr)
+
+proc inputPatterns: seq[Pattern] =
+  var args = commandLineParams()
+  result.setLen(args.len)
+  for i, input in args:
+    try: result[i] = input.parsePreserves.parsePattern
+    except ValueError:
+      quit "failed to parse Preserves argument"
+
+type DumpEntity {.final.} = ref object of Entity
+  assertions: Table[Handle, seq[Value]]
+
+proc toLine(values: seq[Value]; prefix: char): string =
+  result = newStringOfCap(1024)
+  let sep = getEnv("FS", " ")
+  result.add(prefix)
+  for v in values:
+    add(result, sep)
+    add(result, $v)
+  add(result, '\n')
+
+method publish(dump: DumpEntity; turn: var Turn; ass: AssertionRef; h: Handle) =
+  var values = ass.value.sequence
+  stdout.write(values.toLine('+'))
+  stdout.flushFile()
+  dump.assertions[h] = values
+
+method retract(dump: DumpEntity; turn: var Turn; h: Handle) =
+  var values: seq[Value]
+  if dump.assertions.pop(h, values):
+    stdout.write(values.toLine('-'))
+    stdout.flushFile()
+
+method message*(dump: DumpEntity; turn: var Turn; ass: AssertionRef) =
+  stdout.write(ass.value.sequence.toLine('!'))
+  stdout.flushFile()
+
+proc exitProc() {.noconv.} =
+  stdout.write('\n')
+  quit()
+
+proc main =
+  let
+    patterns = inputPatterns()
+    entity = DumpEntity()
+  runActor("syndex_card") do (turn: var Turn):
+    resolveEnvironment(turn) do (turn: var Turn; ds: Cap):
+      for pat in patterns:
+        discard observe(turn, ds, pat, entity)
+
+setControlCHook(exitProc)
+main()

syndicate_utils.nimble

@@ -5,7 +5,7 @@ author        = "Emery Hemingway"
 description   = "Utilites for Syndicated Actors and Synit"
 license       = "unlicense"
 srcDir        = "src"
-bin           = @["mintsturdyref", "mount_actor", "msg", "postgre_actor", "preserve_process_environment", "rofi_script_actor", "sqlite_actor", "syndesizer", "xslt_actor"]
+bin           = @["mintsturdyref", "mount_actor", "msg", "postgre_actor", "preserve_process_environment", "rofi_script_actor", "sqlite_actor", "syndesizer", "syndump", "xslt_actor"]
 
 
 # Dependencies