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Code Issues Packages Projects Releases Wiki Activity

FIX: Skip GitHub linkback when topic is already linked (#37633)

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The GitHub linkback feature posts comments on PRs/issues/commits when
they are mentioned in Discourse posts. However, it never checked whether
the GitHub PR/issue/commit already contained a link back to the same
Discourse topic (in its description or existing comments). This led to
redundant linkback comments when a PR already referenced the topic.

Before posting a linkback comment, we now fetch the PR/issue body and
existing comments (or commit comments) from the GitHub API and check
whether any of them already contain a URL pointing to the same Discourse
topic. URL matching uses Discourse.route_for — the same mechanism used
by the oneboxer, search, and TopicLink — to reliably recognize all topic
URL formats (/t/slug/id, /t/id, /t/id/post_number, etc.).

On any GitHub API error, the check fails open (still posts the linkback)
to preserve the pre-existing behavior — and because if the GET fails,
the subsequent POST will likely fail too.
This commit is contained in:
Régis Hanol
2026-02-09 14:31:27 +01:00
committed by GitHub
parent 936cf2ebc3
commit 318eb49a30
2 changed files with 282 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files
plugins/discourse-github/app/lib/github_linkback.rb
+60
View File
@@ -135,6 +135,9 @@ class GithubLinkback
def post_pr_or_issue(link, type)
pr_or_issue_number = link.pr_number || link.issue_number
return if topic_already_linked_on_github?(link)
github_url =
"https://api.github.com/repos/#{link.project}/issues/#{pr_or_issue_number}/comments"
comment =
@@ -148,6 +151,8 @@ class GithubLinkback
end
def post_commit(link)
return if topic_already_linked_on_github?(link)
github_url = "https://api.github.com/repos/#{link.project}/commits/#{link.sha}/comments"
comment =
@@ -160,6 +165,61 @@ class GithubLinkback
Excon.post(github_url, body: { body: comment }.to_json, headers: headers)
end
def topic_already_linked_on_github?(link)
texts =
if link.type == :commit
fetch_commit_comment_texts(link.project, link.sha)
else
fetch_pr_or_issue_texts(link.project, link.pr_number || link.issue_number)
end
texts.any? { |text| text_links_to_topic?(text) }
rescue Excon::Error
false
end
def fetch_commit_comment_texts(project, sha)
response =
Excon.get(
"https://api.github.com/repos/#{project}/commits/#{sha}/comments?per_page=100",
headers:,
expects: [200],
)
JSON.parse(response.body).map { |comment| comment["body"].to_s }
end
def fetch_pr_or_issue_texts(project, number)
issue_response =
Excon.get(
"https://api.github.com/repos/#{project}/issues/#{number}",
headers:,
expects: [200],
)
comments_response =
Excon.get(
"https://api.github.com/repos/#{project}/issues/#{number}/comments?per_page=100",
headers:,
expects: [200],
)
[
JSON.parse(issue_response.body)["body"].to_s,
*JSON.parse(comments_response.body).map { |comment| comment["body"].to_s },
]
end
def text_links_to_topic?(text)
base_url = Discourse.base_url
text
.scan(%r{#{Regexp.escape(base_url)}/t/\S+})
.any? do |url|
route = Discourse.route_for(url)
route && route[:controller] == "topics" && route[:action] == "show" &&
(route[:id] || route[:topic_id]).to_i == @post.topic_id
end
end
def headers
{
"Content-Type" => "application/json",
plugins/discourse-github/spec/lib/github_linkback_spec.rb
+222 -11
View File
@@ -200,6 +200,15 @@ describe GithubLinkback do
end
describe "#create" do
let(:github_api_headers) do
{
"Authorization" => "token abcdef",
"Content-Type" => "application/json",
"Host" => "api.github.com",
"User-Agent" => "Discourse-Github-Linkback",
}
end
before { SiteSetting.github_linkback_projects = "discourse/discourse|discourse/*" }
it "returns an empty array without an access token" do
@@ -207,13 +216,11 @@ describe GithubLinkback do
end
context "with an access token" do
let(:headers) do
{
"Authorization" => "token abcdef",
"Content-Type" => "application/json",
"Host" => "api.github.com",
"User-Agent" => "Discourse-Github-Linkback",
}
let(:empty_json_response) do
{ status: 200, body: "[]", headers: { "Content-Type" => "application/json" } }
end
let(:empty_body_json_response) do
{ status: 200, body: '{"body":""}', headers: { "Content-Type" => "application/json" } }
end
before do
@@ -222,22 +229,34 @@ describe GithubLinkback do
stub_request(
:post,
"https://api.github.com/repos/discourse/discourse/commits/76981605fa10975e2e7af457e2f6a31909e0c811/comments",
).with(headers: headers).to_return(status: 200, body: "", headers: {})
).with(headers: github_api_headers).to_return(status: 200, body: "", headers: {})
stub_request(
:post,
"https://api.github.com/repos/discourse/discourse/issues/123/comments",
).with(headers: headers).to_return(status: 200, body: "", headers: {})
).with(headers: github_api_headers).to_return(status: 200, body: "", headers: {})
stub_request(
:post,
"https://api.github.com/repos/discourse/discourse/issues/701/comments",
).with(headers: headers).to_return(status: 200, body: "", headers: {})
).with(headers: github_api_headers).to_return(status: 200, body: "", headers: {})
stub_request(
:post,
"https://api.github.com/repos/discourse/discourse-github-linkback/issues/3/comments",
).with(headers: headers).to_return(status: 200, body: "", headers: {})
).with(headers: github_api_headers).to_return(status: 200, body: "", headers: {})
stub_request(:get, %r{https://api\.github\.com/repos/.+/commits/.+/comments}).to_return(
empty_json_response,
)
stub_request(:get, %r{https://api\.github\.com/repos/.+/issues/\d+$}).to_return(
empty_body_json_response,
)
stub_request(:get, %r{https://api\.github\.com/repos/.+/issues/\d+/comments}).to_return(
empty_json_response,
)
end
it "returns the URLs it linked to and creates custom fields" do
@@ -282,5 +301,197 @@ describe GithubLinkback do
expect(links.size).to eq(1)
end
end
context "when topic is already linked on GitHub" do
let(:pr_post) { Fabricate(:post, raw: github_pr_link) }
let(:issue_post) { Fabricate(:post, raw: github_issue_link) }
let(:commit_post) { Fabricate(:post, raw: github_commit_link) }
before { SiteSetting.github_linkback_access_token = "abcdef" }
it "skips linkback when the PR description already contains a link to the topic" do
topic_url = "#{Discourse.base_url}/t/#{pr_post.topic.slug}/#{pr_post.topic_id}"
stub_request(:get, "https://api.github.com/repos/discourse/discourse/issues/701").with(
headers: github_api_headers,
).to_return(
status: 200,
body: { body: "This PR implements #{topic_url}" }.to_json,
headers: {
"Content-Type" => "application/json",
},
)
stub_request(
:get,
"https://api.github.com/repos/discourse/discourse/issues/701/comments?per_page=100",
).with(headers: github_api_headers).to_return(
status: 200,
body: [].to_json,
headers: {
"Content-Type" => "application/json",
},
)
links = GithubLinkback.new(pr_post).create
expect(links.size).to eq(1)
expect(
a_request(:post, "https://api.github.com/repos/discourse/discourse/issues/701/comments"),
).not_to have_been_made
end
it "skips linkback when an existing comment contains a link to the topic" do
topic_url = "#{Discourse.base_url}/t/#{issue_post.topic_id}/3"
stub_request(:get, "https://api.github.com/repos/discourse/discourse/issues/123").with(
headers: github_api_headers,
).to_return(
status: 200,
body: { body: "Some unrelated description" }.to_json,
headers: {
"Content-Type" => "application/json",
},
)
stub_request(
:get,
"https://api.github.com/repos/discourse/discourse/issues/123/comments?per_page=100",
).with(headers: github_api_headers).to_return(
status: 200,
body: [{ body: "Already discussed at #{topic_url}" }].to_json,
headers: {
"Content-Type" => "application/json",
},
)
links = GithubLinkback.new(issue_post).create
expect(links.size).to eq(1)
expect(
a_request(:post, "https://api.github.com/repos/discourse/discourse/issues/123/comments"),
).not_to have_been_made
end
it "skips linkback for commits when an existing comment links to the topic" do
topic_url = "#{Discourse.base_url}/t/#{commit_post.topic_id}"
stub_request(
:get,
"https://api.github.com/repos/discourse/discourse/commits/76981605fa10975e2e7af457e2f6a31909e0c811/comments?per_page=100",
).with(headers: github_api_headers).to_return(
status: 200,
body: [{ body: "Discussed in #{topic_url}" }].to_json,
headers: {
"Content-Type" => "application/json",
},
)
links = GithubLinkback.new(commit_post).create
expect(links.size).to eq(1)
expect(
a_request(
:post,
"https://api.github.com/repos/discourse/discourse/commits/76981605fa10975e2e7af457e2f6a31909e0c811/comments",
),
).not_to have_been_made
end
end
context "when topic is not already linked on GitHub" do
let(:pr_post) { Fabricate(:post, raw: github_pr_link) }
let(:commit_post) { Fabricate(:post, raw: github_commit_link) }
before { SiteSetting.github_linkback_access_token = "abcdef" }
it "posts linkback when existing links point to a different topic" do
different_topic_url = "#{Discourse.base_url}/t/some-other-topic/999999"
stub_request(:get, "https://api.github.com/repos/discourse/discourse/issues/701").with(
headers: github_api_headers,
).to_return(
status: 200,
body: { body: "See #{different_topic_url}" }.to_json,
headers: {
"Content-Type" => "application/json",
},
)
stub_request(
:get,
"https://api.github.com/repos/discourse/discourse/issues/701/comments?per_page=100",
).with(headers: github_api_headers).to_return(
status: 200,
body: [].to_json,
headers: {
"Content-Type" => "application/json",
},
)
stub_request(
:post,
"https://api.github.com/repos/discourse/discourse/issues/701/comments",
).with(headers: github_api_headers).to_return(status: 200, body: "", headers: {})
links = GithubLinkback.new(pr_post).create
expect(links.size).to eq(1)
expect(
a_request(:post, "https://api.github.com/repos/discourse/discourse/issues/701/comments"),
).to have_been_made.once
end
it "posts linkback when the GitHub API check fails (fail open)" do
stub_request(:get, "https://api.github.com/repos/discourse/discourse/issues/701").with(
headers: github_api_headers,
).to_return(status: 404, body: "", headers: {})
stub_request(
:get,
"https://api.github.com/repos/discourse/discourse/issues/701/comments?per_page=100",
).with(headers: github_api_headers).to_return(status: 404, body: "", headers: {})
stub_request(
:post,
"https://api.github.com/repos/discourse/discourse/issues/701/comments",
).with(headers: github_api_headers).to_return(status: 200, body: "", headers: {})
links = GithubLinkback.new(pr_post).create
expect(links.size).to eq(1)
expect(
a_request(:post, "https://api.github.com/repos/discourse/discourse/issues/701/comments"),
).to have_been_made.once
end
it "posts linkback for commits when no existing comment links to the topic" do
stub_request(
:get,
"https://api.github.com/repos/discourse/discourse/commits/76981605fa10975e2e7af457e2f6a31909e0c811/comments?per_page=100",
).with(headers: github_api_headers).to_return(
status: 200,
body: [{ body: "Some unrelated comment" }].to_json,
headers: {
"Content-Type" => "application/json",
},
)
stub_request(
:post,
"https://api.github.com/repos/discourse/discourse/commits/76981605fa10975e2e7af457e2f6a31909e0c811/comments",
).with(headers: github_api_headers).to_return(status: 200, body: "", headers: {})
links = GithubLinkback.new(commit_post).create
expect(links.size).to eq(1)
expect(
a_request(
:post,
"https://api.github.com/repos/discourse/discourse/commits/76981605fa10975e2e7af457e2f6a31909e0c811/comments",
),
).to have_been_made.once
end
end
end
end