Create each language through a LanguageFactory.

functions_in_file asks the factory for a language instance instead of constructing the language itself.

examples/crapper.edn

@@ -185,7 +185,8 @@
     {:name "declared_namespace", :text "declared_namespace"}
     {:name "namespace_from_path", :text "namespace_from_path"}
     {:name "functions_in_source", :text "functions_in_source"}
-    {:name "Clojure", :text "Clojure"}],
+    {:name "Clojure", :text "Clojure"}
+    {:name "ClojureFactory", :text "ClojureFactory"}],
    :level 1,
    :lang :python,
    :id :languages.clojure}
@@ -195,7 +196,8 @@
    :ops
    [{:name "package_namespace", :text "package_namespace"}
     {:name "functions_in_source", :text "functions_in_source"}
-    {:name "Go", :text "Go"}],
+    {:name "Go", :text "Go"}
+    {:name "GoFactory", :text "GoFactory"}],
    :level 1,
    :lang :python,
    :id :languages.golang}
@@ -204,14 +206,19 @@
    :file "src/crapper/languages/java.py",
    :ops
    [{:name "functions_in_source", :text "functions_in_source"}
-    {:name "Java", :text "Java"}],
+    {:name "Java", :text "Java"}
+    {:name "JavaFactory", :text "JavaFactory"}],
    :level 1,
    :lang :python,
    :id :languages.java}
   {:ns "crapper.languages.language",
    :name "Language",
    :file "src/crapper/languages/language.py",
-   :ops [{:name "Language", :text "Language"} {:name "Unknown", :text "Unknown"}],
+   :ops
+   [{:name "Language", :text "Language"}
+    {:name "Unknown", :text "Unknown"}
+    {:name "LanguageFactory", :text "LanguageFactory"}
+    {:name "UnknownFactory", :text "UnknownFactory"}],
    :level 1,
    :lang :python,
    :id :languages.language}
@@ -220,7 +227,8 @@
    :file "src/crapper/languages/python.py",
    :ops
    [{:name "functions_in_source", :text "functions_in_source"}
-    {:name "Python", :text "Python"}],
+    {:name "Python", :text "Python"}
+    {:name "PythonFactory", :text "PythonFactory"}],
    :level 1,
    :lang :python,
    :id :languages.python}
@@ -229,7 +237,8 @@
    :file "src/crapper/languages/rust.py",
    :ops
    [{:name "functions_in_source", :text "functions_in_source"}
-    {:name "Rust", :text "Rust"}],
+    {:name "Rust", :text "Rust"}
+    {:name "RustFactory", :text "RustFactory"}],
    :level 1,
    :lang :python,
    :id :languages.rust}
@@ -254,7 +263,8 @@
    :file "src/crapper/languages/typescript.py",
    :ops
    [{:name "functions_in_source", :text "functions_in_source"}
-    {:name "TypeScript", :text "TypeScript"}],
+    {:name "TypeScript", :text "TypeScript"}
+    {:name "TypeScriptFactory", :text "TypeScriptFactory"}],
    :level 1,
    :lang :python,
    :id :languages.typescript}

src/crapper/languages/__init__.py

@@ -1,27 +1,27 @@
 """Per-language function extraction."""
 
-from crapper.languages.clojure import Clojure
-from crapper.languages.golang import Go
-from crapper.languages.java import Java
-from crapper.languages.language import Unknown
-from crapper.languages.python import Python
-from crapper.languages.rust import Rust
-from crapper.languages.typescript import TypeScript
+from crapper.languages.clojure import ClojureFactory
+from crapper.languages.golang import GoFactory
+from crapper.languages.java import JavaFactory
+from crapper.languages.language import LanguageFactory, UnknownFactory
+from crapper.languages.python import PythonFactory
+from crapper.languages.rust import RustFactory
+from crapper.languages.typescript import TypeScriptFactory
 from crapper.model import Function
 
-_LANGUAGES = {
-    "clojure": Clojure(),
-    "java": Java(),
-    "go": Go(),
-    "typescript": TypeScript(),
-    "python": Python(),
-    "rust": Rust(),
+_FACTORIES: dict[str, LanguageFactory] = {
+    "clojure": ClojureFactory(),
+    "java": JavaFactory(),
+    "go": GoFactory(),
+    "typescript": TypeScriptFactory(),
+    "python": PythonFactory(),
+    "rust": RustFactory(),
 }
-_UNKNOWN = Unknown()
+_UNKNOWN = UnknownFactory()
 
 
 def functions_in_file(
     language: str, source: str, path: str, project_root: str
 ) -> list[Function]:
-    chosen = _LANGUAGES.get(language, _UNKNOWN)
-    return chosen.functions(source, path, project_root)
+    factory = _FACTORIES.get(language, _UNKNOWN)
+    return factory.create().functions(source, path, project_root)

src/crapper/languages/clojure.py

@@ -7,7 +7,7 @@ variants, `and`, `or`, `loop`, `catch`, and each clause of `cond`, `condp`,
 
 import re
 
-from crapper.languages.language import Language
+from crapper.languages.language import Language, LanguageFactory
 from crapper.model import Function
 
 _DECISION = re.compile(
@@ -291,3 +291,8 @@ def functions_in_source(
 class Clojure(Language):
     def functions(self, source: str, path: str, project_root: str) -> list[Function]:
         return functions_in_source(source, path, project_root)
+
+
+class ClojureFactory(LanguageFactory):
+    def create(self) -> Language:
+        return Clojure()

src/crapper/languages/golang.py

@@ -19,7 +19,7 @@ from crapper.languages.treesitter import (
     parse,
     start_line,
 )
-from crapper.languages.language import Language
+from crapper.languages.language import Language, LanguageFactory
 from crapper.model import Function
 
 _DECISIONS = {
@@ -155,3 +155,8 @@ def functions_in_source(
 class Go(Language):
     def functions(self, source: str, path: str, project_root: str) -> list[Function]:
         return functions_in_source(source, path, project_root)
+
+
+class GoFactory(LanguageFactory):
+    def create(self) -> Language:
+        return Go()

src/crapper/languages/java.py

@@ -17,7 +17,7 @@ from crapper.languages.treesitter import (
     parse,
     start_line,
 )
-from crapper.languages.language import Language
+from crapper.languages.language import Language, LanguageFactory
 from crapper.model import Function
 
 _PACKAGE = re.compile(r"(?m)^\s*package\s+([a-zA-Z_][\w.]*)\s*;")
@@ -120,3 +120,8 @@ def functions_in_source(source: str, path: str) -> list[Function]:
 class Java(Language):
     def functions(self, source: str, path: str, project_root: str) -> list[Function]:
         return functions_in_source(source, path)
+
+
+class JavaFactory(LanguageFactory):
+    def create(self) -> Language:
+        return Java()

src/crapper/languages/language.py

@@ -1,4 +1,4 @@
-"""The operation every language implements."""
+"""The language operation, and the factories that create language instances."""
 
 from abc import ABC, abstractmethod
 
@@ -14,3 +14,14 @@ class Language(ABC):
 class Unknown(Language):
     def functions(self, source: str, path: str, project_root: str) -> list[Function]:
         return []
+
+
+class LanguageFactory(ABC):
+    @abstractmethod
+    def create(self) -> Language:
+        """A language instance ready to read source files."""
+
+
+class UnknownFactory(LanguageFactory):
+    def create(self) -> Language:
+        return Unknown()

src/crapper/languages/python.py

@@ -16,7 +16,7 @@ from crapper.languages.treesitter import (
     parse,
     start_line,
 )
-from crapper.languages.language import Language
+from crapper.languages.language import Language, LanguageFactory
 from crapper.model import Function
 
 _DECISIONS = {
@@ -137,3 +137,8 @@ def functions_in_source(
 class Python(Language):
     def functions(self, source: str, path: str, project_root: str) -> list[Function]:
         return functions_in_source(source, path, project_root)
+
+
+class PythonFactory(LanguageFactory):
+    def create(self) -> Language:
+        return Python()

src/crapper/languages/rust.py

@@ -20,7 +20,7 @@ from crapper.languages.treesitter import (
     parse,
     start_line,
 )
-from crapper.languages.language import Language
+from crapper.languages.language import Language, LanguageFactory
 from crapper.model import Function
 
 _DECISIONS = {
@@ -192,3 +192,8 @@ def functions_in_source(
 class Rust(Language):
     def functions(self, source: str, path: str, project_root: str) -> list[Function]:
         return functions_in_source(source, path, project_root)
+
+
+class RustFactory(LanguageFactory):
+    def create(self) -> Language:
+        return Rust()

src/crapper/languages/typescript.py

@@ -17,7 +17,7 @@ from crapper.languages.treesitter import (
     parse,
     start_line,
 )
-from crapper.languages.language import Language
+from crapper.languages.language import Language, LanguageFactory
 from crapper.model import Function
 
 _DECISIONS = {
@@ -184,3 +184,8 @@ def functions_in_source(
 class TypeScript(Language):
     def functions(self, source: str, path: str, project_root: str) -> list[Function]:
         return functions_in_source(source, path, project_root)
+
+
+class TypeScriptFactory(LanguageFactory):
+    def create(self) -> Language:
+        return TypeScript()