Fix ErrorEvent factory

Parsed result of Sentry stack trace is already a value of:

```
raw_result['stacktrace']['frames']
```

app/controllers/projects/error_tracking_controller.rb

@@ -77,8 +77,10 @@ class Projects::ErrorTrackingController < Projects::ApplicationController
 
     return if handle_errors(result)
 
+    result_with_syntax_highlight = Gitlab::ErrorTracking::StackTraceHighlightDecorator.decorate(result[:latest_event])
+
     render json: {
-      error: serialize_error_event(result[:latest_event])
+      error: serialize_error_event(result_with_syntax_highlight)
     }
   end
 

changelogs/unreleased/35411-syntax-highlight-for-sentry-stacktrace.yml

+---
+title: Add syntax highlight for Sentry error stack trace
+merge_request: 21182
+author:
+type: added

lib/gitlab/error_tracking/stack_trace_highlight_decorator.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module ErrorTracking
+    module StackTraceHighlightDecorator
+      extend self
+
+      def decorate(error_event)
+        ::Gitlab::ErrorTracking::ErrorEvent.new(
+          issue_id: error_event.issue_id,
+          date_received: error_event.date_received,
+          stack_trace_entries: highlight_stack_trace(error_event.stack_trace_entries)
+        )
+      end
+
+      private
+
+      def highlight_stack_trace(stack_trace)
+        stack_trace.map do |entry|
+          highlight_stack_trace_entry(entry)
+        end
+      end
+
+      def highlight_stack_trace_entry(entry)
+        return entry unless entry['context']
+
+        entry.merge('context' => highlight_entry_context(entry['filename'], entry['context']))
+      end
+
+      def highlight_entry_context(filename, context)
+        language = Rouge::Lexer.guess_by_filename(filename).tag
+
+        context.map do |line_number, line_of_code|
+          [
+            line_number,
+            # Passing nil for the blob name allows skipping linking dependencies for the line_of_code
+            Gitlab::Highlight.highlight(nil, line_of_code, language: language)
+          ]
+        end
+      end
+    end
+  end
+end

spec/controllers/projects/error_tracking_controller_spec.rb

@@ -384,6 +384,10 @@ describe Projects::ErrorTrackingController do
       ).permit!
     end
 
+    subject(:get_stack_trace) do
+      get :stack_trace, params: issue_params(issue_id: issue_id, format: :json)
+    end
+
     before do
       expect(ErrorTracking::IssueLatestEventService)
         .to receive(:new).with(project, user, permitted_params)
@@ -398,7 +402,7 @@ describe Projects::ErrorTrackingController do
         end
 
         it 'returns no data' do
-          get :stack_trace, params: issue_params(issue_id: issue_id, format: :json)
+          get_stack_trace
 
           expect(response).to have_gitlab_http_status(:no_content)
         end
@@ -408,16 +412,21 @@ describe Projects::ErrorTrackingController do
         before do
           expect(issue_stack_trace_service).to receive(:execute)
             .and_return(status: :success, latest_event: error_event)
+
+          get_stack_trace
         end
 
         let(:error_event) { build(:error_tracking_error_event) }
 
         it 'returns an error' do
-          get :stack_trace, params: issue_params(issue_id: issue_id, format: :json)
-
           expect(response).to have_gitlab_http_status(:ok)
           expect(response).to match_response_schema('error_tracking/issue_stack_trace')
-          expect(json_response['error']).to eq(error_event.as_json)
+        end
+
+        it 'highlights stack trace source code' do
+          expect(json_response['error']).to eq(
+            Gitlab::ErrorTracking::StackTraceHighlightDecorator.decorate(error_event).as_json
+          )
         end
       end
 
@@ -431,7 +440,7 @@ describe Projects::ErrorTrackingController do
           end
 
           it 'returns 400 with message' do
-            get :stack_trace, params: issue_params(issue_id: issue_id, format: :json)
+            get_stack_trace
 
             expect(response).to have_gitlab_http_status(:bad_request)
             expect(json_response['message']).to eq(error_message)
@@ -450,7 +459,7 @@ describe Projects::ErrorTrackingController do
           end
 
           it 'returns http_status with message' do
-            get :stack_trace, params: issue_params(issue_id: issue_id, format: :json)
+            get_stack_trace
 
             expect(response).to have_gitlab_http_status(http_status)
             expect(json_response['message']).to eq(error_message)

spec/factories/error_tracking/error_event.rb

@@ -5,12 +5,40 @@ FactoryBot.define do
     issue_id { 'id' }
     date_received { Time.now.iso8601 }
     stack_trace_entries do
-      {
-        'stacktrace' =>
-          {
-            'frames' => [{ 'file' => 'test.rb' }]
-          }
-      }
+      [
+        {
+          'function' => 'puts',
+          'lineNo' => 14,
+          'filename' => 'hello_world.rb',
+          'context' => [
+            [10, "# Ruby example\n"],
+            [11, "class HelloWorld\n"],
+            [12, "  def self.message\n"],
+            [13, "    @name = 'World'\n"],
+            [14, "    puts \"Hello \#{@name}\"\n"],
+            [15, "  end\n"],
+            [16, "end\n"]
+          ]
+        },
+        {
+          'function' => 'print',
+          'lineNo' => 6,
+          'filename' => 'HelloWorld.swift',
+          'context' => [
+            [1, "// Swift example\n"],
+            [2, "struct HelloWorld {\n"],
+            [3, "    let name = \"World\"\n"],
+            [4, "\n"],
+            [5, "    static func message() {\n"],
+            [6, "        print(\"Hello, \\(self.name)\")\n"],
+            [7, "    }\n"],
+            [8, "}\n"]
+          ]
+        },
+        {
+          'filename' => 'blank.txt'
+        }
+      ]
     end
 
     skip_create

spec/fixtures/api/schemas/error_tracking/error_stack_trace.json

@@ -7,7 +7,7 @@
   ],
   "properties": {
     "issue_id": { "type": ["string", "integer"] },
-    "stack_trace_entries": { "type": "object" },
+    "stack_trace_entries": { "type": "array" },
     "date_received": { "type": "string" }
   },
   "additionalProperties": false

spec/lib/gitlab/error_tracking/stack_trace_highlight_decorator_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::ErrorTracking::StackTraceHighlightDecorator do
+  let(:error_event) { build(:error_tracking_error_event) }
+
+  describe '.decorate' do
+    subject(:decorate) { described_class.decorate(error_event) }
+
+    it 'does not change issue_id' do
+      expect(decorate.issue_id).to eq(error_event.issue_id)
+    end
+
+    it 'does not change date_received' do
+      expect(decorate.date_received).to eq(error_event.date_received)
+    end
+
+    it 'decorates the stack trace context' do
+      expect(decorate.stack_trace_entries).to eq(
+        [
+          {
+            'function' => 'puts',
+            'lineNo' => 14,
+            'filename' => 'hello_world.rb',
+            'context' => [
+              [10, '<span id="LC1" class="line" lang="ruby"><span class="c1"># Ruby example</span></span>'],
+              [11, '<span id="LC1" class="line" lang="ruby"><span class="k">class</span> <span class="nc">HelloWorld</span></span>'],
+              [12, '<span id="LC1" class="line" lang="ruby">  <span class="k">def</span> <span class="nc">self</span><span class="o">.</span><span class="nf">message</span></span>'],
+              [13, '<span id="LC1" class="line" lang="ruby">    <span class="vi">@name</span> <span class="o">=</span> <span class="s1">\'World\'</span></span>'],
+              [14, %Q[<span id="LC1" class="line" lang="ruby">    <span class="nb">puts</span> <span class="s2">"Hello </span><span class="si">\#{</span><span class="vi">@name</span><span class="si">}</span><span class="s2">"</span></span>]],
+              [15, '<span id="LC1" class="line" lang="ruby">  <span class="k">end</span></span>'],
+              [16, '<span id="LC1" class="line" lang="ruby"><span class="k">end</span></span>']
+            ]
+          },
+          {
+            'function' => 'print',
+            'lineNo' => 6,
+            'filename' => 'HelloWorld.swift',
+            'context' => [
+              [1, '<span id="LC1" class="line" lang="swift"><span class="c1">// Swift example</span></span>'],
+              [2, '<span id="LC1" class="line" lang="swift"><span class="kd">struct</span> <span class="kt">HelloWorld</span> <span class="p">{</span></span>'],
+              [3, '<span id="LC1" class="line" lang="swift">    <span class="k">let</span> <span class="nv">name</span> <span class="o">=</span> <span class="s">"World"</span></span>'],
+              [4, '<span id="LC1" class="line" lang="swift"></span>'],
+              [5, '<span id="LC1" class="line" lang="swift">    <span class="kd">static</span> <span class="kd">func</span> <span class="nf">message</span><span class="p">()</span> <span class="p">{</span></span>'],
+              [6, '<span id="LC1" class="line" lang="swift">        <span class="nf">print</span><span class="p">(</span><span class="s">"Hello, </span><span class="se">\\(</span><span class="k">self</span><span class="o">.</span><span class="n">name</span><span class="se">)</span><span class="s">"</span><span class="p">)</span></span>'],
+              [7, '<span id="LC1" class="line" lang="swift">    <span class="p">}</span></span>'],
+              [8, '<span id="LC1" class="line" lang="swift"><span class="p">}</span></span>']
+            ]
+          },
+          {
+            'filename' => 'blank.txt'
+          }
+        ]
+      )
+    end
+  end
+end