1 files changed, 182 insertions, 0 deletions
diff --git a/lib/bundler/vendor/pub_grub/lib/pub_grub/failure_writer.rb b/lib/bundler/vendor/pub_grub/lib/pub_grub/failure_writer.rb
new file mode 100644
index 0000000000..ee099b23f4
--- /dev/null
+++ b/lib/bundler/vendor/pub_grub/lib/pub_grub/failure_writer.rb
@@ -0,0 +1,182 @@
+module Bundler::PubGrub
+  class FailureWriter
+    def initialize(root)
+      @root = root
+
+      # { Incompatibility => Integer }
+      @derivations = {}
+
+      # [ [ String, Integer or nil ] ]
+      @lines = []
+
+      # { Incompatibility => Integer }
+      @line_numbers = {}
+
+      count_derivations(root)
+    end
+
+    def write
+      return @root.to_s unless @root.conflict?
+
+      visit(@root)
+
+      padding = @line_numbers.empty? ? 0 : "(#{@line_numbers.values.last}) ".length
+
+      @lines.map do |message, number|
+        next "" if message.empty?
+
+        lead = number ? "(#{number}) " : ""
+        lead = lead.ljust(padding)
+        message = message.gsub("\n", "\n" + " " * (padding + 2))
+        "#{lead}#{message}"
+      end.join("\n")
+    end
+
+    private
+
+    def write_line(incompatibility, message, numbered:)
+      if numbered
+        number = @line_numbers.length + 1
+        @line_numbers[incompatibility] = number
+      end
+
+      @lines << [message, number]
+    end
+
+    def visit(incompatibility, conclusion: false)
+      raise unless incompatibility.conflict?
+
+      numbered = conclusion || @derivations[incompatibility] > 1;
+      conjunction = conclusion || incompatibility == @root ? "So," : "And"
+
+      cause = incompatibility.cause
+
+      if cause.conflict.conflict? && cause.other.conflict?
+        conflict_line = @line_numbers[cause.conflict]
+        other_line = @line_numbers[cause.other]
+
+        if conflict_line && other_line
+          write_line(
+            incompatibility,
+            "Because #{cause.conflict} (#{conflict_line})\nand #{cause.other} (#{other_line}),\n#{incompatibility}.",
+            numbered: numbered
+          )
+        elsif conflict_line || other_line
+          with_line    = conflict_line ? cause.conflict : cause.other
+          without_line = conflict_line ? cause.other : cause.conflict
+          line = @line_numbers[with_line]
+
+          visit(without_line);
+          write_line(
+            incompatibility,
+            "#{conjunction} because #{with_line} (#{line}),\n#{incompatibility}.",
+            numbered: numbered
+          )
+        else
+          single_line_conflict = single_line?(cause.conflict.cause)
+          single_line_other    = single_line?(cause.other.cause)
+
+          if single_line_conflict || single_line_other
+            first  = single_line_other ? cause.conflict : cause.other
+            second = single_line_other ? cause.other : cause.conflict
+            visit(first)
+            visit(second)
+            write_line(
+              incompatibility,
+              "Thus, #{incompatibility}.",
+              numbered: numbered
+            )
+          else
+            visit(cause.conflict, conclusion: true)
+            @lines << ["", nil]
+            visit(cause.other)
+
+            write_line(
+              incompatibility,
+              "#{conjunction} because #{cause.conflict} (#{@line_numbers[cause.conflict]}),\n#{incompatibility}.",
+              numbered: numbered
+            )
+          end
+        end
+      elsif cause.conflict.conflict? || cause.other.conflict?
+        derived = cause.conflict.conflict? ? cause.conflict : cause.other
+        ext     = cause.conflict.conflict? ? cause.other : cause.conflict
+
+        derived_line = @line_numbers[derived]
+        if derived_line
+          write_line(
+            incompatibility,
+            "Because #{ext}\nand #{derived} (#{derived_line}),\n#{incompatibility}.",
+            numbered: numbered
+          )
+        elsif collapsible?(derived)
+          derived_cause = derived.cause
+          if derived_cause.conflict.conflict?
+            collapsed_derived = derived_cause.conflict
+            collapsed_ext = derived_cause.other
+          else
+            collapsed_derived = derived_cause.other
+            collapsed_ext = derived_cause.conflict
+          end
+
+          visit(collapsed_derived)
+
+          write_line(
+            incompatibility,
+            "#{conjunction} because #{collapsed_ext}\nand #{ext},\n#{incompatibility}.",
+            numbered: numbered
+          )
+        else
+          visit(derived)
+          write_line(
+            incompatibility,
+            "#{conjunction} because #{ext},\n#{incompatibility}.",
+            numbered: numbered
+          )
+        end
+      else
+        write_line(
+          incompatibility,
+          "Because #{cause.conflict}\nand #{cause.other},\n#{incompatibility}.",
+          numbered: numbered
+        )
+      end
+    end
+
+    def single_line?(cause)
+      !cause.conflict.conflict? && !cause.other.conflict?
+    end
+
+    def collapsible?(incompatibility)
+      return false if @derivations[incompatibility] > 1
+
+      cause = incompatibility.cause
+      # If incompatibility is derived from two derived incompatibilities,
+      # there are too many transitive causes to display concisely.
+      return false if cause.conflict.conflict? && cause.other.conflict?
+
+      # If incompatibility is derived from two external incompatibilities, it
+      # tends to be confusing to collapse it.
+      return false unless cause.conflict.conflict? || cause.other.conflict?
+
+      # If incompatibility's internal cause is numbered, collapsing it would
+      # get too noisy.
+      complex = cause.conflict.conflict? ? cause.conflict : cause.other
+
+      !@line_numbers.has_key?(complex)
+    end
+
+    def count_derivations(incompatibility)
+      if @derivations.has_key?(incompatibility)
+        @derivations[incompatibility] += 1
+      else
+        @derivations[incompatibility] = 1
+        if incompatibility.conflict?
+          cause = incompatibility.cause
+          count_derivations(cause.conflict)
+          count_derivations(cause.other)
+        end
+      end
+    end
+  end
+end