Allow setting content for resolutions

When reading conflicts:

1. Add a `type` field. `text` works as before, and has `sections`;
   `text-editor` is a file with ambiguous conflict markers that can only
   be resolved in an editor.
2. Add a `content_path` field pointing to a JSON representation of the
   file's content for a single file.
3. Hitting `content_path` returns a similar datastructure to the `file`,
   but without the `content_path` and `sections` fields, and with a
   `content` field containing the full contents of the file (with
   conflict markers).

When writing conflicts:

1. Instead of `sections` being at the top level, they are now in a
   `files` array. This matches the read format better.
2. The `files` array contains file hashes, each of which must contain:
   a. `new_path`
   b. `old_path`
   c. EITHER `sections` (which works as before) or `content` (with the
      full content of the resolved file).

4 files changed, 63 insertions, 13 deletions

diff --git a/lib/gitlab/conflict/file.rb b/lib/gitlab/conflict/file.rb
index dff9e29c6a5..26a9f170298 100644
--- a/lib/gitlab/conflict/file.rb
+++ b/lib/gitlab/conflict/file.rb
@@ -4,12 +4,12 @@ module Gitlab
       include Gitlab::Routing.url_helpers
       include IconsHelper
 
-      class MissingResolution < StandardError
+      class MissingResolution < ResolutionError
       end
 
       CONTEXT_LINES = 3
 
-      attr_reader :merge_file_result, :their_path, :our_path, :our_mode, :merge_request, :repository
+      attr_reader :merge_file_result, :their_path, :our_path, :our_mode, :merge_request, :repository, :type
 
       def initialize(merge_file_result, conflict, merge_request:)
         @merge_file_result = merge_file_result
@@ -21,12 +21,24 @@ module Gitlab
         @match_line_headers = {}
       end
 
+      def content
+        merge_file_result[:data]
+      end
+
       # Array of Gitlab::Diff::Line objects
       def lines
-        @lines ||= Gitlab::Conflict::Parser.new.parse(merge_file_result[:data],
+        return @lines if defined?(@lines)
+
+        begin
+          @type = 'text'
+          @lines = Gitlab::Conflict::Parser.new.parse(content,
                                                       our_path: our_path,
                                                       their_path: their_path,
                                                       parent_file: self)
+        rescue Gitlab::Conflict::Parser::ParserError
+          @type = 'text-editor'
+          @lines = nil
+        end
       end
 
       def resolve_lines(resolution)
@@ -53,6 +65,14 @@ module Gitlab
         end.compact
       end
 
+      def resolve_content(resolution)
+        if resolution == content
+          raise MissingResolution, "Resolved content has no changes for file #{our_path}"
+        end
+
+        resolution
+      end
+
       def highlight_lines!
         their_file = lines.reject { |line| line.type == 'new' }.map(&:text).join("\n")
         our_file = lines.reject { |line| line.type == 'old' }.map(&:text).join("\n")
@@ -170,21 +190,36 @@ module Gitlab
         match_line.text = "@@ -#{match_line.old_pos},#{line.old_pos} +#{match_line.new_pos},#{line.new_pos} @@#{header}"
       end
 
-      def as_json(opts = nil)
-        {
+      def as_json(opts = {})
+        json_hash = {
           old_path: their_path,
           new_path: our_path,
           blob_icon: file_type_icon_class('file', our_mode, our_path),
           blob_path: namespace_project_blob_path(merge_request.project.namespace,
                                                  merge_request.project,
-                                                 ::File.join(merge_request.diff_refs.head_sha, our_path)),
-          sections: sections
+                                                 ::File.join(merge_request.diff_refs.head_sha, our_path))
         }
+
+        if opts[:full_content]
+          json_hash.merge(content: content)
+        else
+          json_hash.merge!(sections: sections) if type == 'text'
+
+          json_hash.merge(type: type, content_path: content_path)
+        end
+      end
+
+      def content_path
+        conflict_for_path_namespace_project_merge_request_path(merge_request.project.namespace,
+                                                               merge_request.project,
+                                                               merge_request,
+                                                               old_path: their_path,
+                                                               new_path: our_path)
       end
 
       # Don't try to print merge_request or repository.
       def inspect
-        instance_variables = [:merge_file_result, :their_path, :our_path, :our_mode].map do |instance_variable|
+        instance_variables = [:merge_file_result, :their_path, :our_path, :our_mode, :type].map do |instance_variable|
           value = instance_variable_get("@#{instance_variable}")
 
           "#{instance_variable}=\"#{value}\""
diff --git a/lib/gitlab/conflict/file_collection.rb b/lib/gitlab/conflict/file_collection.rb
index bbd0427a2c8..fa5bd4649d4 100644
--- a/lib/gitlab/conflict/file_collection.rb
+++ b/lib/gitlab/conflict/file_collection.rb
@@ -30,6 +30,10 @@ module Gitlab
         end
       end
 
+      def file_for_path(old_path, new_path)
+        files.find { |file| file.their_path == old_path && file.our_path == new_path }
+      end
+
       def as_json(opts = nil)
         {
           target_branch: merge_request.target_branch,
diff --git a/lib/gitlab/conflict/parser.rb b/lib/gitlab/conflict/parser.rb
index 98e842cded3..ddd657903fb 100644
--- a/lib/gitlab/conflict/parser.rb
+++ b/lib/gitlab/conflict/parser.rb
@@ -1,19 +1,24 @@
 module Gitlab
   module Conflict
     class Parser
-      class ParserError < StandardError
+      class UnresolvableError < StandardError
       end
 
-      class UnexpectedDelimiter < ParserError
+      class UnmergeableFile < UnresolvableError
       end
 
-      class MissingEndDelimiter < ParserError
+      class UnsupportedEncoding < UnresolvableError
+      end
+
+      # Recoverable errors - the conflict can be resolved in an editor, but not with
+      # sections.
+      class ParserError < StandardError
       end
 
-      class UnmergeableFile < ParserError
+      class UnexpectedDelimiter < ParserError
       end
 
-      class UnsupportedEncoding < ParserError
+      class MissingEndDelimiter < ParserError
       end
 
       def parse(text, our_path:, their_path:, parent_file: nil)
diff --git a/lib/gitlab/conflict/resolution_error.rb b/lib/gitlab/conflict/resolution_error.rb
new file mode 100644
index 00000000000..a0f2006bc24
--- /dev/null
+++ b/lib/gitlab/conflict/resolution_error.rb
@@ -0,0 +1,6 @@
+module Gitlab
+  module Conflict
+    class ResolutionError < StandardError
+    end
+  end
+end