patterns: add Literal[T] type for literal capture

src/syndicate/patterns.nim

@@ -289,6 +289,43 @@ proc grabDictionary*(bindings: sink openArray[(string, Pattern)]): Pattern =
   for (key, val) in bindings.items:
     result.dcompound.dict.entries[key.toSymbol(Cap)] = val
 
+func depattern(comp: DCompound): Preserve[Cap]
+
+func depattern(pat: Pattern): Preserve[Cap] =
+  case pat.orKind
+  of PatternKind.DDiscard, PatternKind.DBind:
+    discard
+  of PatternKind.DLit:
+    result = pat.dlit.value.toPreserve(Cap)
+  of PatternKind.DCompound:
+    result = depattern(pat.dcompound)
+
+func depattern(comp: DCompound): Preserve[Cap] =
+  case comp.orKind
+  of DCompoundKind.rec:
+    result = initRecord(comp.rec.label, comp.rec.fields.len)
+    for i, f in comp.rec.fields:
+      result[i] = depattern(f)
+  of DCompoundKind.arr:
+    result = initSequence(comp.arr.items.len, Cap)
+    for i, e in comp.arr.items:
+      result[i] = depattern(e)
+  of DCompoundKind.dict:
+    result = initDictionary(Cap)
+    for key, val in comp.dict.entries:
+      result[key] = depattern(val)
+
+type Literal*[T] = object
+  ## A wrapper type to deserialize patterns to native values.
+  value*: T
+
+proc fromPreserveHook*[T, E](lit: var Literal[T]; pr: Preserve[E]): bool =
+  var pat: Pattern
+  pat.fromPreserve(pr) and lit.value.fromPreserve(depattern pat)
+
+proc toPreserveHook*[T](lit: Literal[T]; E: typedesc): Preserve[E] =
+  lit.grab.toPreserve(E)
+
 type
   Path* = seq[Value]
   Paths* = seq[Path]

syndicate.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version = "20231013"
+version = "20231014"
 author        = "Emery Hemingway"
 description   = "Syndicated actors for conversational concurrency"
 license       = "Unlicense"

tests/test_patterns.nim

@@ -1,7 +1,7 @@
 # SPDX-FileCopyrightText: ☭ Emery Hemingway
 # SPDX-License-Identifier: Unlicense
 
-import std/unittest
+import std/[tables, unittest]
 
 import preserves, syndicate
 from syndicate/protocols/dataspace import Observe
@@ -34,3 +34,25 @@ test "dictionaries":
 
   let values = capture(pat, source)
   check $values == "@[1, 2, 3]"
+
+type
+  File {.preservesDictionary.} = object
+    name: string
+    path: string
+    size: BiggestInt
+    `type`: string
+  Files = Table[Symbol, File]
+  Fields = Table[Symbol, string]
+
+  Request {.preservesRecord: "request".} = object
+    seq: BiggestInt
+    fields: Fields
+    files: Files
+
+test "literals":
+  const txt = """<rec request [<lit 3> <dict {artists: <lit "kyyyyym"> date: <lit "2023-10-14"> notes: <lit "Lots of stuff"> title: <lit "Domes show">}> <dict {front-cover: <dict {name: <lit "ADULT_TIME_Glielmi.jpg"> path: <lit "/tmp/652adad1b3d2b666dcc8d857.jpg"> size: <lit 255614> type: <lit "image/jpeg">}>}>]>"""
+  var pr = parsePreserves(txt, Cap)
+
+  var capture: Literal[Request]
+  check capture.fromPreserve(pr)
+  echo capture.value