feat(lang): def REGISTRY from "file.lres" - a game fills an open registry from its own file

The entries are read and checked against the registry's record as a
registry ... from file is, errors at the resource file's line, and they
are defs of the module that wrote the line: the registry must be open to
it, and they take that module's place in the stable order. Reseed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

LANGUAGE.md

@@ -400,6 +400,22 @@ The entries are compiled in: nothing is parsed at start-up, and a build that suc
 every resource it uses. The path is the project's (where the build runs), else beside the file that
 declares the registry.
 
+
+A module that extends an open registry can bring its entries from a resource file of its own:
+
+```ludic
+# doc-check: skip — the file it names is beside the example
+import "crafting"                 # module crafting: export open registry Recipes of Recipe as RC
+def Recipes from "recipes.lres"   # the game's recipes, after crafting's own
+```
+
+`def REGISTRY from "file.lres"` reads the file as `registry ... from` does - the project's path, else
+beside the file that says it - and checks every entry against the registry's record, an error
+naming the resource file's own line (`bad_recipes.lres:3: error: field minutes of Recipe wants an
+int and this is a string`). Its entries are defs of the module that wrote the line, so the registry
+must be open (and exported) to it, and they take that module's place in the order: the declaring
+module's entries, then each other module's by module name, and within a file, file order.
+
 ### Default parameters, and calls that name what they change
 
 A parameter can have a default, and a call leaves out what it does not change - the last ones when

changes/def-from-resource.md

@@ -0,0 +1,7 @@
+bump: minor
+type: feature
+**`def Recipes from "recipes.lres"` - a game fills a package's open registry from its own resource
+file.** The entries are checked against the registry's record as the file is read, with errors at
+the resource file's line, and they are defs of the module that wrote the line: the registry must be
+open to it, and they sit in the stable order (the declaring module's entries, then other modules'
+by name, and file order within a file).

examples/modules/crafting/index.ludic

@@ -0,0 +1,9 @@
+# crafting/index.ludic - a registry the game may add to, and the package's own first entry
+module crafting
+export property Recipe {
+  key: string = ""
+  name: string = ""
+  minutes: int = 0
+}
+export open registry Recipes of Recipe as RC
+def Recipes rope { name: "Rope", minutes: 10 }

examples/modules/recipes.lres

@@ -0,0 +1,3 @@
+# recipes.lres - the game's own recipes, added to crafting's open registry
+tea { name: "Pine tea", minutes: 5 }
+splint { name: "Splint", minutes: 20 }

examples/modules/registry_extend.ludic

@@ -0,0 +1,12 @@
+# registry_extend.ludic — L8 + L9: a game fills a package's open registry from its own resource
+# file with `def Recipes from "recipes.lres"`. The entries are checked against Recipe as the file
+# is read, and they come after the package's own, in file order.
+#
+# Running it prints:  3 Rope Pine tea Splint 20
+import "crafting"
+program RegistryExtend {
+  def Recipes from "recipes.lres"
+  entry {
+    print(`{RC_COUNT} {Recipes[0].name} {Recipes[RC_TEA].name} {Recipes[2].name} {Recipes[recipes_find("splint")].minutes}`)
+  }
+}

examples/rejected/bad_recipes.lres

@@ -0,0 +1,3 @@
+# bad_recipes.lres - the second entry gives minutes as text
+tea { name: "Pine tea", minutes: 5 }
+splint { name: "Splint", minutes: "twenty" }

examples/rejected/craft_kit/index.ludic

@@ -0,0 +1,8 @@
+# craft_kit/index.ludic - an open registry of recipes
+module crafting
+export property Recipe {
+  key: string = ""
+  name: string = ""
+  minutes: int = 0
+}
+export open registry Recipes of Recipe as RC

examples/rejected/registry_extend_field.ludic

@@ -0,0 +1,8 @@
+# L8 + L9: a resource file that extends a registry is checked against its record, at its own line
+import "craft_kit"
+program RegistryExtendField {
+  def Recipes from "bad_recipes.lres"
+  entry {
+    print(RC_COUNT)
+  }
+}

selfhost/frontend/registry.ludic

@@ -75,9 +75,16 @@ function parse_registry() -> void {
   if from != null { res_read(v, from) }
 }
 # def REGISTRY key { field: value, ... }
+# def REGISTRY from "file.lres" - every entry of a resource file, as defs of this file's module
 function parse_def() -> void {
   pi += 1
   let reg = eat_id()
+  if is_id("from") and toks[pi + 1].kind == TK_STR {
+    let from = toks[pi + 1].text
+    pi += 2
+    res_read_into(reg, from, `def {reg} from`)
+    return
+  }
   let key = eat_id()
   skipnl()
   let rec = record()

selfhost/frontend/resource.ludic

@@ -16,9 +16,14 @@ function res_path(from: pointer, declaring: pointer) -> pointer {
   return join_path(dir_of(declaring), from)
 }
 function res_read(v: Node, from: pointer) -> void {
+  res_read_into(v.s, from, `registry {v.s}`)
+}
+# the entries of a resource file into registry `reg`, as defs of the reading file's module: a
+# registry's own file, or `def REG from "file.lres"` in a module that extends an open registry
+function res_read_into(reg: pointer, from: pointer, who: pointer) -> void {
   let path = res_path(from, g_parse_file)
   let src = read_file(path)
-  if src == null { perr(`registry {v.s}: cannot read the resource file {from}`) }
+  if src == null { perr(`{who}: cannot read the resource file {from}`) }
   let saved_toks = toks
   let saved_pi = pi
   let saved_file = g_parse_file
@@ -36,7 +41,7 @@ function res_read(v: Node, from: pointer) -> void {
     let key = eat_id()
     skipnl()
     let rec = record()
-    push(g_df_reg, v.s)
+    push(g_df_reg, reg)
     push(g_df_key, key)
     push(g_df_rec, rec)
   }

tools/ludic-cli/test.ludic

@@ -820,6 +820,8 @@ function cmd_dev_test() -> int {
   feat_case("modules/open_registry", "", "clock animals weather / 2 2 3", "open_registry.ludic (L8+L3: an open registry takes other modules' defs; its own entries first, then by module name)")
   reject_case("rejected/registry_closed", "registry Tools is not open to other modules", "a def from another module into a registry that is not open is refused")
   reject_case("rejected/registry_hidden", "Tools is private to module kit", "a def goes through visibility: the registry must be exported")
+  feat_case("modules/registry_extend", "", "3 Rope Pine tea Splint 20", "registry_extend.ludic (L8+L9: `def Recipes from \"recipes.lres\"` fills a package's open registry from the game's file)")
+  reject_case("rejected/registry_extend_field", "bad_recipes.lres:3: error: field minutes of Recipe wants an int", "a resource file extending a registry is checked at its own line")
   feat_case("lang/resources", "", "2 Axe 2 Split 10 0 1", "resources.ludic (L9: a registry read from a resource file at compile time, nested records typed by the schema)")
   reject_case("rejected/resource_field", "bad_tools.lres:3: error: field weight of Tool wants a float", "a resource file's entry is checked at its own line")
   reject_case("rejected/resource_missing", "cannot read the resource file data/no_such.lres", "a registry's resource file must exist")