Add lowest_prerelease_suffix method (#10832)

* Add lowest_prerelease_suffix method

* Apply change to python

common/lib/dependabot/version.rb

@@ -52,7 +52,7 @@ def ignored_patch_versions
     def ignored_minor_versions
       parts = to_semver.split(".")
       version_parts = parts.fill("0", parts.length...2)
-      lower_parts = version_parts.first(1) + [version_parts[1].to_i + 1] + ["a"]
+      lower_parts = version_parts.first(1) + [version_parts[1].to_i + 1] + [lowest_prerelease_suffix]
       upper_parts = version_parts.first(0) + [version_parts[0].to_i + 1]
       lower_bound = ">= #{lower_parts.join('.')}"
       upper_bound = "< #{upper_parts.join('.')}"
@@ -63,10 +63,15 @@ def ignored_minor_versions
     sig { overridable.returns(T::Array[String]) }
     def ignored_major_versions
       version_parts = to_semver.split(".")
-      lower_parts = [version_parts[0].to_i + 1] + ["a"]
+      lower_parts = [version_parts[0].to_i + 1] + [lowest_prerelease_suffix]
       lower_bound = ">= #{lower_parts.join('.')}"
 
       [lower_bound]
     end
+
+    sig { returns(String) }
+    def lowest_prerelease_suffix
+      "a"
+    end
   end
 end

common/spec/dependabot/version_spec.rb

@@ -7,6 +7,14 @@
 RSpec.describe Dependabot::Version do
   subject(:version) { described_class.new(version_string) }
 
+  describe "#lowest_prerelease_suffix" do
+    subject(:ignored_versions) { version.lowest_prerelease_suffix }
+
+    let(:version_string) { "1.2.3-alpha.1" }
+
+    it { is_expected.to eq "a" }
+  end
+
   describe "#ignored_major_versions" do
     subject(:ignored_versions) { version.ignored_major_versions }
 

maven/lib/dependabot/maven/version.rb

@@ -65,6 +65,11 @@ def prerelease?
         end
       end
 
+      sig { returns(String) }
+      def lowest_prerelease_suffix
+        "a0"
+      end
+
       sig { params(other: VersionParameter).returns(Integer) }
       def <=>(other)
         other = Dependabot::Maven::Version.new(other.to_s) unless other.is_a? Dependabot::Maven::Version
@@ -78,7 +83,7 @@ def ignored_patch_versions
 
         version_parts = parts.fill("0", parts.length...2)
         # the a0 is so we can get the next earliest prerelease patch version
-        upper_parts = version_parts.first(1) + [version_parts[1].to_i + 1] + ["a0"]
+        upper_parts = version_parts.first(1) + [version_parts[1].to_i + 1] + [lowest_prerelease_suffix]
         lower_bound = "> #{to_semver}"
         upper_bound = "< #{upper_parts.join('.')}"
 
@@ -91,8 +96,8 @@ def ignored_minor_versions
         return [] if parts.empty? # for non-semver versions
 
         version_parts = parts.fill("0", parts.length...2)
-        lower_parts = version_parts.first(1) + [version_parts[1].to_i + 1] + ["a0"]
-        upper_parts = version_parts.first(0) + [version_parts[0].to_i + 1] + ["a0"]
+        lower_parts = version_parts.first(1) + [version_parts[1].to_i + 1] + [lowest_prerelease_suffix]
+        upper_parts = version_parts.first(0) + [version_parts[0].to_i + 1] + [lowest_prerelease_suffix]
         lower_bound = ">= #{lower_parts.join('.')}"
         upper_bound = "< #{upper_parts.join('.')}"
 
@@ -104,7 +109,7 @@ def ignored_major_versions
         version_parts = token_bucket.tokens # e.g [1,2,3] if version is 1.2.3-alpha3
         return [] if version_parts.empty? # for non-semver versions
 
-        lower_parts = [version_parts[0].to_i + 1] + ["a0"] # earliest next major version prerelease
+        lower_parts = [version_parts[0].to_i + 1] + [lowest_prerelease_suffix] # earliest next major version prerelease
         lower_bound = ">= #{lower_parts.join('.')}"
 
         [lower_bound]

maven/spec/dependabot/maven/version_spec.rb

@@ -559,6 +559,14 @@
     it { is_expected.to eq(["> #{version_string}, < 1.3.a0"]) }
   end
 
+  describe "#lowest_prerelease_suffix" do
+    subject(:ignored_versions) { version.lowest_prerelease_suffix }
+
+    let(:version_string) { "1.2.3-alpha.1" }
+
+    it { is_expected.to eq "a0" }
+  end
+
   describe "compatibility with Gem::Requirement" do
     subject { requirement.satisfied_by?(version) }
 

python/lib/dependabot/python/version.rb

@@ -254,6 +254,11 @@ def dev_cmp_key
         T.must(dev)
       end
 
+      sig { returns(String) }
+      def lowest_prerelease_suffix
+        "dev0"
+      end
+
       private
 
       sig { params(other: Dependabot::Python::Version).returns(Integer) }

python/spec/dependabot/python/version_spec.rb

@@ -342,6 +342,14 @@
     end
   end
 
+  describe "#lowest_prerelease_suffix" do
+    subject { version.lowest_prerelease_suffix }
+
+    let(:version_string) { "1.2.3" }
+
+    it { is_expected.to eq "dev0" }
+  end
+
   describe "compatibility with Gem::Requirement" do
     subject { requirement.satisfied_by?(version) }