DEV: Support version operators in .discourse-compatibility (#22714)

This adds support for the `<=` and `<` version operators in `.discourse-compatibility` files. This allows for more flexibility (e.g. targeting the entire 3.1.x stable release via `< 3.2.0.beta1`), and should also make compatibility files to be more readable.

If an operator is not specified we default to `<=`, which matches the old behavior.

lib/version.rb

@@ -31,7 +31,7 @@ module Discourse
   #  2.5.0.beta2: bbffee
   #  2.4.4.beta6: some-other-branch-ref
   #  2.4.2.beta1: v1-tag
-  def self.find_compatible_resource(version_list, version = ::Discourse::VERSION::STRING)
+  def self.find_compatible_resource(version_list, target_version = ::Discourse::VERSION::STRING)
     return unless version_list.present?
 
     begin
@@ -41,21 +41,37 @@ module Discourse
 
     raise InvalidVersionListError unless version_list.is_a?(Hash)
 
-    version_list = version_list.sort_by { |v, pin| Gem::Version.new(v) }.reverse
+    version_list =
+      version_list
+        .transform_keys do |v|
+          Gem::Requirement.parse(v)
+        rescue Gem::Requirement::BadRequirementError => e
+          raise InvalidVersionListError, "Invalid version specifier: #{v}"
+        end
+        .sort_by do |parsed_requirement, _|
+          operator, version = parsed_requirement
+          [version, operator == "<" ? 0 : 1]
+        end
 
-    # If plugin compat version is listed as less than current Discourse version, take the version/hash listed before.
-    checkout_version = nil
-    version_list.each do |core_compat, target|
-      if Gem::Version.new(core_compat) == Gem::Version.new(version) # Exact version match - return it
-        checkout_version = target
-        break
-      elsif Gem::Version.new(core_compat) < Gem::Version.new(version) # Core is on a higher version than listed, use a later version
-        break
+    parsed_target_version = Gem::Version.new(target_version)
+
+    lowest_matching_entry =
+      version_list.find do |parsed_requirement, target|
+        req_operator, req_version = parsed_requirement
+        req_operator = "<=" if req_operator == "="
+
+        if !%w[<= <].include?(req_operator)
+          raise InvalidVersionListError,
+                "Invalid version specifier operator for '#{req_operator} #{req_version}'. Operator must be one of <= or <"
+        end
+
+        resolved_requirement = Gem::Requirement.new("#{req_operator} #{req_version.to_s}")
+        resolved_requirement.satisfied_by?(parsed_target_version)
       end
-      checkout_version = target
-    end
 
-    return if checkout_version.nil?
+    return if lowest_matching_entry.nil?
+
+    checkout_version = lowest_matching_entry[1]
 
     begin
       Discourse::Utils.execute_command "git",

spec/lib/version_spec.rb

@@ -103,6 +103,54 @@ RSpec.describe Discourse::VERSION do
         YML
       include_examples "test compatible resource"
     end
+
+    context "with different version operators" do
+      let(:version_list) { <<~YML }
+        <= 3.2.0.beta1: lteBeta1
+        3.2.0.beta2: lteBeta2
+        < 3.2.0.beta4: ltBeta4
+        <= 3.2.0.beta4: lteBeta4
+      YML
+
+      it "supports <= operator" do
+        expect(Discourse.find_compatible_resource(version_list, "3.2.0.beta1")).to eq("lteBeta1")
+        expect(Discourse.find_compatible_resource(version_list, "3.2.0.beta0")).to eq("lteBeta1")
+      end
+
+      it "defaults to <= operator" do
+        expect(Discourse.find_compatible_resource(version_list, "3.2.0.beta2")).to eq("lteBeta2")
+      end
+
+      it "supports < operator" do
+        expect(Discourse.find_compatible_resource(version_list, "3.2.0.beta3")).to eq("ltBeta4")
+        expect(Discourse.find_compatible_resource(version_list, "3.2.0.beta4")).not_to eq("ltBeta4")
+      end
+
+      it "prioritises <= over <, regardless of file order" do
+        expect(Discourse.find_compatible_resource(version_list, "3.2.0.beta3")).to eq("ltBeta4")
+        expect(
+          Discourse.find_compatible_resource(version_list.lines.reverse.join("\n"), "3.2.0.beta3"),
+        ).to eq("ltBeta4")
+      end
+
+      it "raises error for >= operator" do
+        expect { Discourse.find_compatible_resource(">= 3.1.0: test", "3.1.0") }.to raise_error(
+          Discourse::InvalidVersionListError,
+        )
+      end
+
+      it "raises error for ~> operator" do
+        expect { Discourse.find_compatible_resource("~> 3.1.0: test", "3.1.0") }.to raise_error(
+          Discourse::InvalidVersionListError,
+        )
+      end
+
+      it "raises error for invalid version" do
+        expect { Discourse.find_compatible_resource("1.1.: test", "3.1.0") }.to raise_error(
+          Discourse::InvalidVersionListError,
+        )
+      end
+    end
   end
 
   describe ".find_compatible_git_resource" do