Fix; raise error on missing title before changes

Author: mdwint

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Raise error on missing title before changes.
 - Strip trailing whitespace from text.
 
 
@@ -32,7 +33,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
-- Raise error on wrong title level for changes.
+- Raise error on wrong title level before changes.
 - Raise error on duplicate version sections.
 - Merge duplicate changes sections.
 
@@ -48,7 +49,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-- Print output on success.
+- Print message on success.
 
 ### Changed
 

ocdc/parser.py

@@ -252,21 +252,26 @@ def version(p: Parser) -> Tuple[ast.Version, Token]:
         else:
             v.changes[key] = changes_
 
-    detect_wrong_title_level(p, 3)
+    detect_wrong_title_level(p, 3, "before changes")
 
     return v, title_token
 
 
-def detect_wrong_title_level(p: Parser, expected: int) -> None:
+def detect_wrong_title_level(p: Parser, expected: int, reason: str) -> None:
     with p.checkpoint():
         level = p.match_many(TokenType.HASH)
-        if level and level != expected:
+        if level != expected:
             token = p.peek(1)
             p.match({TokenType.TEXT})
             skip_newlines(p)
             if p.match({TokenType.DASH}):
-                msg = f"Expected a title of H{expected}, but found H{level}"
-                raise p.error(msg, token, back=level)
+                msg = f"Expected a title of H{expected} {reason}"
+                if level:
+                    msg += f", but found H{level}"
+                    raise p.error(msg, token, back=level)
+                else:
+                    token = p.peek(1)
+                    raise p.error(msg, token, back=len(token.text))
         raise p.Rollback
 
 

tests/data/wrong_title_level.err.txt

@@ -1,4 +1,4 @@
-Expected a title of H3, but found H2 at line 14, column 1:
+Expected a title of H3 before changes, but found H2 at line 14, column 1:
 
   ## Removed
   ^^

tests/data/wrong_title_level_none.err.md

@@ -0,0 +1,18 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+
+## Unreleased
+
+- Experimental stuff.
+
+
+## 0.1.0 - 2022-08-04
+
+### Added
+
+- Something.

tests/data/wrong_title_level_none.err.txt

@@ -0,0 +1,4 @@
+Expected a title of H3 before changes at line 11, column 1:
+
+  - Experimental stuff.
+  ^