Cache reports by hledger version

app/controllers/hledger/reports_controller.rb

@@ -28,7 +28,8 @@ module ::Hledger
       end
 
       first_post = @topic.first_post
-      cache_key = cache_key_for(first_post, report_type, begin_date, end_date)
+      runner = Hledger::Runner.new
+      cache_key = cache_key_for(runner, first_post, report_type, begin_date, end_date)
 
       if (cached = Discourse.cache.read(cache_key))
         return render(json: cached)
@@ -41,7 +42,7 @@ module ::Hledger
           begin_date: begin_date,
           end_date: end_date,
         },
-        runner: Hledger::Runner.new,
+        runner: runner,
       ) do
         on_success do |report:|
           Discourse.cache.write(cache_key, report, expires_in: CACHE_TTL)
@@ -103,7 +104,7 @@ module ::Hledger
       :invalid
     end
 
-    def cache_key_for(first_post, report_type, begin_date, end_date)
+    def cache_key_for(runner, first_post, report_type, begin_date, end_date)
       [
         "hledger",
         @topic.id,
@@ -112,6 +113,7 @@ module ::Hledger
         begin_date,
         end_date,
         SiteSetting.hledger_path,
+        runner.version,
       ].join(":")
     end
 

lib/hledger/runner.rb

@@ -41,7 +41,7 @@ module Hledger
     def version
       return @version if defined?(@version)
 
-      @version = detect_version
+      @version = detect_version_cached
     end
 
     def execute(argv, stdin_data: nil)
@@ -183,6 +183,20 @@ module Hledger
       result.stdout[/\d+\.\d+(?:\.\d+)?/]
     end
 
+    # The version is part of the report cache key, so remember it to avoid a
+    # `--version` subprocess on every request.
+    def detect_version_cached
+      return detect_version if @path.blank?
+
+      key = "hledger:version:#{@path}"
+      cached = Discourse.cache.read(key)
+      return cached if cached
+
+      detected = detect_version
+      Discourse.cache.write(key, detected, expires_in: 10.minutes) if detected
+      detected
+    end
+
     def failure_result
       Result.new(
         success: false,

spec/requests/hledger/reports_spec.rb

@@ -129,6 +129,16 @@ RSpec.describe Hledger::ReportsController do
     expect(response.status).to eq(422)
   end
 
+  it "includes the hledger version in the cache key" do
+    get_report("accounts")
+    expect(response.parsed_body.dig("meta", "hledger_version")).to eq("1.52.1")
+
+    allow(Hledger::Runner).to receive(:new).and_return(StubHledgerRunner.new(version: "1.53.0"))
+
+    get_report("accounts")
+    expect(response.parsed_body.dig("meta", "hledger_version")).to eq("1.53.0")
+  end
+
   it "rejects journals with include directives" do
     post.update!(raw: "```hledger\ninclude /etc/passwd\n```")