From 26d08ebfead5532ada0afbb8c044a498cb9a5a8d Mon Sep 17 00:00:00 2001
From: Doug Miller <doug@douglas-miller.com>
Date: Fri, 19 Feb 2021 00:06:56 -0600
Subject: [PATCH] Fixing 'stack level too deep error' in commits_in_tag

---
 .../octo_fetcher.rb                           | 47 ++++++++++++-------
 spec/unit/octo_fetcher_spec.rb                | 43 +++++++++++++++++
 2 files changed, 72 insertions(+), 18 deletions(-)

diff --git a/lib/github_changelog_generator/octo_fetcher.rb b/lib/github_changelog_generator/octo_fetcher.rb
index fb36b6aa4..028aa9ffe 100644
--- a/lib/github_changelog_generator/octo_fetcher.rb
+++ b/lib/github_changelog_generator/octo_fetcher.rb
@@ -41,6 +41,7 @@ def initialize(options = {})
       @branches     = nil
       @graph        = nil
       @client = nil
+      @commits_in_tag_cache = {}
     end
 
     def middleware
@@ -342,35 +343,45 @@ def commits_in_branch(name)
       end
     end
 
-    def commits_in_tag(sha, shas = Set.new)
-      @graph ||= commits.map { |commit| [commit["sha"], commit] }.to_h
-
-      return if shas.include?(sha)
-
-      shas << sha
-
-      if (top = @graph[sha])
-        top[:parents].each do |parent|
-          commits_in_tag(parent[:sha], shas)
-        end
-      end
-
-      shas
-    end
-
     # Fetch all SHAs occurring in or before a given tag and add them to
     # "shas_in_tag"
     #
     # @param [Array] tags The array of tags.
     # @return [Nil] No return; tags are updated in-place.
     def fetch_tag_shas(tags)
-      tags.each do |tag|
-        tag["shas_in_tag"] = commits_in_tag(tag["commit"]["sha"])
+      # Reverse the tags array to gain max benefit from the @commits_in_tag_cache
+      tags.reverse_each do |tag|
+        tag["shas_in_tag"] = commits_in_tag(tag[:commit][:sha])
       end
     end
 
     private
 
+    def commits_in_tag(sha, shas = Set.new)
+      # Reduce multiple runs for the same tag
+      return @commits_in_tag_cache[sha] if @commits_in_tag_cache.key?(sha)
+
+      @graph ||= commits.map { |commit| [commit[:sha], commit] }.to_h
+      return shas unless (current = @graph[sha])
+
+      queue = [current]
+      while queue.any?
+        commit = queue.shift
+        # If we've already processed this sha, just grab it's parents from the cache
+        if @commits_in_tag_cache.key?(commit[:sha])
+          shas.merge(@commits_in_tag_cache[commit[:sha]])
+        else
+          shas.add(commit[:sha])
+          commit[:parents].each do |p|
+            queue.push(@graph[p[:sha]]) unless shas.include?(p[:sha])
+          end
+        end
+      end
+
+      @commits_in_tag_cache[sha] = shas
+      shas
+    end
+
     def stringify_keys_deep(indata)
       case indata
       when Array
diff --git a/spec/unit/octo_fetcher_spec.rb b/spec/unit/octo_fetcher_spec.rb
index f128872fc..e29f4e7bb 100644
--- a/spec/unit/octo_fetcher_spec.rb
+++ b/spec/unit/octo_fetcher_spec.rb
@@ -85,6 +85,49 @@
     end
   end
 
+  describe "#fetch_tag_shas" do
+    let(:commits) do
+      [
+        { sha: "0", parents: [{ sha: "1" }, { sha: "6" }] },
+        { sha: "1", parents: [{ sha: "2" }] },
+        { sha: "2", parents: [{ sha: "3" }] },
+        { sha: "3", parents: [{ sha: "4" }] },
+        { sha: "4", parents: [{ sha: "5" }] },
+        { sha: "5", parents: [] },
+        { sha: "6", parents: [{ sha: "7" }, { sha: "8" }] },
+        { sha: "7", parents: [{ sha: "9" }, { sha: "10" }] },
+        { sha: "8", parents: [{ sha: "11" }, { sha: "12" }] },
+        { sha: "9", parents: [] },
+        { sha: "10", parents: [] },
+        { sha: "11", parents: [] },
+        { sha: "12", parents: [] }
+      ]
+    end
+
+    let(:tag0) { { name: "tag-0", commit: { sha: "0" } } }
+    let(:tag1) { { name: "tag-1", commit: { sha: "1" } } }
+    let(:tag6) { { name: "tag-6", commit: { sha: "6" } } }
+
+    before do
+      allow(fetcher).to receive(:commits).and_return(commits)
+    end
+
+    it "should find all shas with single parents" do
+      fetcher.fetch_tag_shas([tag1])
+      expect(tag1["shas_in_tag"]).to eq(Set.new(%w[1 2 3 4 5]))
+    end
+
+    it "should find all shas with multiple parents" do
+      fetcher.fetch_tag_shas([tag6])
+      expect(tag6["shas_in_tag"]).to eq(Set.new(%w[6 7 8 9 10 11 12]))
+    end
+
+    it "should find all shas with mixed parents" do
+      fetcher.fetch_tag_shas([tag0])
+      expect(tag0["shas_in_tag"]).to eq(Set.new(%w[0 1 2 3 4 5 6 7 8 9 10 11 12]))
+    end
+  end
+
   describe "#github_fetch_tags" do
     context "when wrong token provided", :vcr do
       let(:options) do