Helper routines for generating source code

This includes "signing" source to detect modifications, and
maintaining user-modified sections. Hooray!

tests/test_generated_source.py

@@ -0,0 +1,110 @@
+import parser.generated_source as generated_source
+
+
+def test_signature():
+    input_source = f"""
+This is a random thing.
+
+Put your slug here: {generated_source.signature_token()}
+
+Here are some more things:
+
+    - Machine Generated
+    - More Machine Gnerated
+{generated_source.begin_manual_section('foo')}
+    - You can edit here!
+{generated_source.end_manual_section()}
+    - But not here.
+{generated_source.begin_manual_section('bar')}
+    - You can edit here too!
+{generated_source.end_manual_section()}
+    - Also not here.
+"""
+    signed = generated_source.sign_generated_source(input_source)
+    assert signed != input_source
+    assert generated_source.is_signed(signed)
+    assert generated_source.validate_signature(signed)
+
+
+def test_manual_changes():
+    input_source = f"""
+This is a random thing.
+
+Put your slug here: {generated_source.signature_token()}
+
+Here are some more things:
+
+    - Machine Generated
+    - More Machine Gnerated
+{generated_source.begin_manual_section('foo')}
+    - XXXXX
+{generated_source.end_manual_section()}
+    - But not here.
+"""
+    signed = generated_source.sign_generated_source(input_source)
+    modified = signed.replace("XXXXX", "YYYYY")
+    assert modified != signed
+
+    assert generated_source.is_signed(modified)
+    assert generated_source.validate_signature(modified)
+
+
+def test_bad_changes():
+    input_source = f"""
+This is a random thing.
+
+Put your slug here: {generated_source.signature_token()}
+
+Here are some more things:
+
+    - Machine Generated
+    - More Machine Gnerated
+{generated_source.begin_manual_section('foo')}
+    - XXXXX
+{generated_source.end_manual_section()}
+    - ZZZZZ
+"""
+    signed = generated_source.sign_generated_source(input_source)
+    modified = signed.replace("ZZZZZ", "YYYYY")
+    assert modified != signed
+
+    assert generated_source.is_signed(modified)
+    assert not generated_source.validate_signature(modified)
+
+
+def test_merge_changes():
+    original_source = f"""
+A
+// {generated_source.begin_manual_section('foo')}
+B
+// {generated_source.end_manual_section()}
+C
+// {generated_source.begin_manual_section('bar')}
+D
+// {generated_source.end_manual_section()}
+"""
+    new_source = f"""
+E
+// {generated_source.begin_manual_section('bar')}
+F
+// {generated_source.end_manual_section()}
+// {generated_source.begin_manual_section('foo')}
+G
+// {generated_source.end_manual_section()}
+H
+"""
+
+    merged = generated_source.merge_existing(original_source, new_source)
+    assert (
+        merged
+        == f"""
+E
+// {generated_source.begin_manual_section('bar')}
+D
+// {generated_source.end_manual_section()}
+// {generated_source.begin_manual_section('foo')}
+B
+// {generated_source.end_manual_section()}
+H
+"""
+    )