let makemessages translate Tetra components' inline templates

fixes #63

tetra/management/commands/makemessages.py

@@ -0,0 +1,90 @@
+import ast
+import os
+
+from django.core.management.commands.makemessages import (
+    Command as MakeMessagesCommand,
+    BuildFile,
+)
+from django.utils.functional import cached_property
+
+
+def mark_for_translation(s):
+    """Mark a string for translation without translating it immediately."""
+    from django.utils.translation import gettext_noop
+
+    return gettext_noop(s)
+
+
+class TetraBuildFile(BuildFile):
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.inline_templates: dict[int, str] = {}
+
+    @cached_property
+    def is_templatized(self):
+        if self.domain == "django":
+            file_ext = os.path.splitext(self.translatable.file)[1]
+            if file_ext == ".py" and (
+                self.translatable.file == "components.py"
+                or "components" in self.translatable.dirpath
+            ):
+                # FIXME: find a proper way to quickly find out if this file contains
+                #  Tetra components.
+                with open(self.translatable.path, "r") as file:
+                    content = file.read()
+                    try:
+                        tree = ast.parse(content)
+                        for node in ast.walk(tree):
+                            if not isinstance(node, ast.ClassDef):
+                                continue
+                            has_component_base = False
+                            # FIXME: use better way to find out if this is a
+                            #  Tetra component
+                            # it could be "tetra.components.Component", or
+                            # "tetra.Component", or a custom "FooComponent" named
+                            # in another way. We just check for the
+                            # name ending in "Component" which is a bit dull...
+                            for base in node.bases:
+                                if isinstance(base, ast.Name) and base.id.endswith(
+                                    "Component"
+                                ):
+                                    has_component_base = True
+                            if has_component_base:
+                                for stmt in node.body:
+                                    targets = []
+                                    if isinstance(stmt, ast.Assign):
+                                        targets = stmt.targets
+                                    elif isinstance(stmt, ast.AnnAssign):
+                                        targets = [stmt.target]
+                                    for target in targets:
+                                        if (
+                                            isinstance(target, ast.Name)
+                                            and target.id == "template"
+                                        ):
+                                            # stmt.value.s now is the
+                                            # template html string which may
+                                            # contain translatable strings
+                                            self.inline_templates[target.lineno] = (
+                                                stmt.value.s
+                                            )
+                                            # if there is at least one
+                                            # template in the component,
+                                            # consider the component file
+                                            # templatized.
+                                            return True
+
+                    except SyntaxError | SyntaxWarning:
+                        # in case of syntax errors/warnings, just ignore this file
+                        return False
+        return super().is_templatized
+
+    def __repr_(self):
+        return "<%s: %s>" % (self.__class__.__name__, self.translatable.path)
+
+
+class Command(MakeMessagesCommand):
+    """Django's makemessages command which includes .py files that contain inline
+    templates within Tetra components."""
+
+    build_file_class = TetraBuildFile