Handle empty changelog files

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Reissue.finalize returns the version and value as an array
 - Documentation on the refined redo method in Gem::Version
 - Limit major numbers to Integers
+- Handle empty changelog files
 
 ## [0.1.2] - 2024-06-08
 

lib/reissue/parser.rb

@@ -30,14 +30,14 @@ def parse
 
     def parse_title(scanner)
       scanner.scan(/# ([\w\s]+)$/)
-      title = scanner[1].strip
+      title = scanner[1].to_s.strip
       {"title" => title}
     end
 
     def parse_preamble(scanner)
       preamble = scanner.scan_until(VERSION_MATCH)
-      preamble = preamble.gsub(VERSION_BREAK, "").strip
-      scanner.unscan
+      preamble = preamble.to_s.gsub(VERSION_BREAK, "").strip
+      scanner.unscan unless preamble.empty?
       {"preamble" => preamble.strip}
     end
 

lib/reissue/printer.rb

@@ -2,8 +2,8 @@ module Reissue
   class Printer
     def initialize(changelog)
       @changelog = changelog
-      @title = @changelog["title"]
-      @preamble = @changelog["preamble"]
+      @title = @changelog["title"] || "Changelog"
+      @preamble = @changelog["preamble"] || "All project changes are documented in this file."
       @versions = versions
     end
 
@@ -29,7 +29,13 @@ def versions
           format_section(section, changes)
         end.join("\n\n")
         [version_string, changes_string].filter_map { |str| str unless str.empty? }.join("\n\n")
-      end.join("\n\n")
+      end.then do |data|
+        if data.empty?
+          "## [0.0.0] - Unreleased"
+        else
+          data.join("\n\n")
+        end
+      end
     end
 
     def format_section(section, changes)

test/test_changelog_updater.rb

@@ -38,6 +38,13 @@ class TestChangelogUpdater < Minitest::Spec
       assert_match(/\[1.1\.0\]/, contents)
       refute_match(/\[1.0\.0\]/, contents)
     end
+
+    it "handles empty changelog files" do
+      @changelog_updater = Reissue::ChangelogUpdater.new(@tempfile.path)
+      @changelog_updater.call("1.0.0", changelog_file: @tempfile.path)
+      contents = @changelog_updater.to_s
+      assert_match(/\[1.0\.0\]/, contents)
+    end
   end
 
   describe "update" do

test/test_printer.rb

@@ -37,5 +37,19 @@ class TestPrinter < Minitest::Spec
         - New feature
       MARKDOWN
     end
+
+    it "handles empty changelogs" do
+      changelog = {
+        "versions" => []
+      }
+      printer = Reissue::Printer.new(changelog)
+      assert_equal(<<~MARKDOWN, printer.to_s)
+        # Changelog
+
+        All project changes are documented in this file.
+
+        ## [0.0.0] - Unreleased
+      MARKDOWN
+    end
   end
 end