[Reader] Add context to parse errors

CHANGELOG.md

@@ -4,7 +4,9 @@
 
 ##### Enhancements
 
-* None.  
+* Add context to parse errors.  
+  [Samuel Giddins](https://github.com/segiddins)
+  [#5](https://github.com/CocoaPods/Nanaimo/issues/5)
 
 ##### Bug Fixes
 

lib/nanaimo/reader.rb

@@ -32,6 +32,32 @@ class ParseError < Error
       # @return [String] The contents of the plist.
       #
       attr_accessor :plist_string
+
+      def to_s
+        "[!] #{super}#{context}"
+      end
+
+      def context(n = 2)
+        line_number, column = location
+        line_number -= 1
+        lines = plist_string.split(NEWLINE)
+
+        s = line_number.succ.to_s.size
+        indent     = "#{' ' * s}#  "
+        indicator  = "#{line_number.succ}>  "
+
+        m =  ::String.new("\n")
+        m << "#{indent}-------------------------------------------\n"
+        m << lines[[line_number - n, 0].max...line_number].map do |l|
+          "#{indent}#{l}\n"
+        end.join
+        m << "#{indicator}#{lines[line_number]}\n"
+        m << ' ' * (column + s + 2) << "^\n"
+        m << Array(lines[line_number.succ..[lines.count.pred, line_number + n].min]).map do |l|
+          l.strip.empty? ? '' : "#{indent}#{l}\n"
+        end.join
+        m << "#{indent}-------------------------------------------\n"
+      end
     end
 
     # @param plist_contents [String]
@@ -73,7 +99,7 @@ def parse!
       root_object = parse_object
 
       eat_whitespace!
-      raise_parser_error ParseError, "unrecognized characters #{@scanner.rest.inspect} after parsing" unless @scanner.eos?
+      raise_parser_error ParseError, 'Found additional characters after parsing the root plist object' unless @scanner.eos?
 
       Nanaimo::Plist.new(root_object, plist_format)
     end
@@ -93,7 +119,7 @@ def read_string_encoding
     def parse_object
       _comment = skip_to_non_space_matching_annotations
       start_pos = @scanner.pos
-      raise_parser_error ParseError, 'Unexpected eos while parsing' if @scanner.eos?
+      raise_parser_error ParseError, 'Unexpected end of string while parsing' if @scanner.eos?
       if @scanner.skip(/\{/)
         parse_dictionary
       elsif @scanner.skip(/\(/)
@@ -112,15 +138,15 @@ def parse_object
 
     def parse_string
       eat_whitespace!
-      unless match = @scanner.scan(%r{[\w/.$-]+}o)
-        raise_parser_error ParseError, "not a valid string at index #{@scanner.pos} (char is #{current_character.inspect})"
+      unless match = @scanner.scan(%r{[\w/.$]+})
+        raise_parser_error ParseError, "Invalid character #{current_character.inspect} in unquoted string"
       end
       Nanaimo::String.new(match, nil)
     end
 
     def parse_quotedstring(quote)
       unless string = @scanner.scan(/(?:([^#{quote}\\]|\\.)*)#{quote}/)
-        raise_parser_error ParseError, "unterminated quoted string started at #{@scanner.pos}, expected #{quote} but never found it"
+        raise_parser_error ParseError, "Unterminated quoted string, expected #{quote} but never found it"
       end
       string = Unicode.unquotify_string(string.chomp!(quote))
       Nanaimo::QuotedString.new(string, nil)
@@ -137,7 +163,7 @@ def parse_array
         eat_whitespace!
         break if @scanner.skip(/\)/)
         unless @scanner.skip(/,/)
-          raise_parser_error ParseError, "Array #{objects} missing ',' in between objects"
+          raise_parser_error ParseError, "Array missing ',' in between objects"
         end
       end
 
@@ -153,7 +179,7 @@ def parse_dictionary
         key = parse_object
         eat_whitespace!
         unless @scanner.skip(/=/)
-          raise_parser_error ParseError, "Dictionary missing value after key #{key.inspect} at index #{@scanner.pos}, expected '=' and got #{current_character.inspect}"
+          raise_parser_error ParseError, "Dictionary missing value for key #{key.as_ruby.inspect}, expected '=' and found #{current_character.inspect}"
         end
 
         value = parse_object
@@ -162,7 +188,7 @@ def parse_dictionary
         eat_whitespace!
         break if @scanner.skip(/}/)
         unless @scanner.skip(/;/)
-          raise_parser_error ParseError, "Dictionary (#{objects}) missing ';' after key-value pair (#{key} = #{value}) at index #{@scanner.pos} (got #{current_character})"
+          raise_parser_error ParseError, "Dictionary missing ';' after key-value pair for #{key.as_ruby.inspect}, found #{current_character.inspect}"
         end
       end
 
@@ -189,7 +215,7 @@ def current_character
 
     def read_singleline_comment
       unless comment = @scanner.scan_until(NEWLINE)
-        raise_parser_error ParseError, "failed to terminate single line comment #{@scanner.rest.inspect}"
+        raise_parser_error ParseError, 'Failed to terminate single line comment'
       end
       comment
     end
@@ -208,7 +234,7 @@ def eat_whitespace!
 
     def read_multiline_comment
       unless annotation = @scanner.scan(%r{(?:.+?)(?=\*/)}m)
-        raise_parser_error ParseError, "#{@scanner.rest.inspect} failed to terminate multiline comment"
+        raise_parser_error ParseError, 'Failed to terminate multiline comment'
       end
       @scanner.skip(%r{\*/})
 

lib/nanaimo/writer.rb

@@ -60,7 +60,7 @@ def write_object(object)
       when Data
         write_data(object)
       else
-        raise "Cannot write #{object} to an ascii plist"
+        raise "Cannot write #{object.inspect} to an ascii plist"
       end
       write_annotation(object) if pretty
       output

spec/nanaimo/reader_spec.rb

@@ -114,14 +114,6 @@ module Nanaimo
           expect(subject).to eq Nanaimo::Dictionary.new({ Nanaimo::String.new('key', '') => Nanaimo::String.new('$PROJECT_DIR/mogenerator/mogenerator', '') }, '')
         end
       end
-
-      describe 'that contain `-`' do
-        let(:unquoted_string) { 'foo/bar-baz' }
-
-        it 'are parsed correctly' do
-          expect(subject).to eq Nanaimo::Dictionary.new({ Nanaimo::String.new('key', '') => Nanaimo::String.new('foo/bar-baz', '') }, '')
-        end
-      end
     end
 
     describe 'quoted strings' do
@@ -147,9 +139,213 @@ module Nanaimo
         let(:data) { '<12 3>' }
 
         it 'raises an informative error' do
-          expect { subject }.to raise_error(Reader::ParseError, 'Data has an uneven number of hex digits')
+          expect { subject }.to raise_error(Reader::ParseError, <<-E)
+[!] Data has an uneven number of hex digits
+ #  -------------------------------------------
+1>  {key = <12 3>}
+            ^
+ #  -------------------------------------------
+          E
+        end
+      end
+    end
+
+    describe 'parse errors' do
+      shared_examples_for 'parse errors' do |name, plist, expected_error|
+        it "raises an informative error #{name}" do
+          if expected_error.is_a?(::String)
+            prefix = expected_error.scan(/^[ \t]*(?=\S)/).min
+            expected_error.gsub!(/^#{prefix}/, '')
+          end
+
+          expect { Reader.new(plist).parse! }
+            .to raise_error(Reader::ParseError) do |e|
+              if e.is_a?(Regexp)
+                expect(e.to_s).to match(expected_error)
+              else
+                expect(e.to_s).to eq(expected_error)
+              end
+            end
         end
       end
+
+      include_examples 'parse errors',
+                       'with a dictionary without an `=`',
+                       '{ a = ; }',
+                       <<-E
+          [!] Invalid character ";" in unquoted string
+           #  -------------------------------------------
+          1>  { a = ; }
+                    ^
+           #  -------------------------------------------
+        E
+
+      include_examples 'parse errors',
+                       'with an unterminated array',
+                       <<-PLIST,
+          (
+            a,
+            b,
+            (
+              c
+            )
+        PLIST
+                       <<-E
+          [!] Array missing ',' in between objects
+           #  -------------------------------------------
+           #                c
+           #              )
+          7>\s\s
+              ^
+           #  -------------------------------------------
+        E
+
+      include_examples 'parse errors',
+                       'with an error in the middle of the plist',
+                       <<-PLIST,
+(
+  #{"a,\n" * 1000}
+  c,
+  d,
+  e,,,
+  f,
+  g,
+  #{"z,\n" * 250}
+  zz
+)
+          PLIST
+                       <<-E
+            [!] Invalid character "," in unquoted string
+                #  -------------------------------------------
+                #    c,
+                #    d,
+            1005>    e,,,
+                       ^
+                #    f,
+                #    g,
+                #  -------------------------------------------
+          E
+
+      include_examples 'parse errors',
+                       'with an array missing a comma between elements',
+                       <<-PLIST,
+ (
+   a,
+   b,
+   (
+     c
+     d
+   )
+ )
+                           PLIST
+                       <<-E
+[!] Array missing ',' in between objects
+ #  -------------------------------------------
+ #     (
+ #       c
+6>       d
+         ^
+ #     )
+ #   )
+ #  -------------------------------------------
+                           E
+
+      include_examples 'parse errors',
+                       'with an unterminated dictionary',
+                       <<-PLIST,
+{
+  a = e;
+  b = j;
+  d = (
+    c
+  );
+                        PLIST
+                       <<-E
+[!] Unexpected end of string while parsing
+ #  -------------------------------------------
+ #      c
+ #    );
+7>\s\s
+    ^
+ #  -------------------------------------------
+                        E
+
+      include_examples 'parse errors',
+                       'with an unterminated dictionary pair',
+                       <<-PLIST,
+{
+  a = e;
+  b = j;
+  d = (
+    c
+  )
+                         PLIST
+                       <<-E
+[!] Dictionary missing ';' after key-value pair for "d", found ""
+ #  -------------------------------------------
+ #      c
+ #    )
+7>\s\s
+    ^
+ #  -------------------------------------------
+                         E
+
+      include_examples 'parse errors',
+                       'with a dictionary without an `=`',
+                       '{a}',
+                       <<-E
+[!] Dictionary missing value for key "a", expected '=' and found "}"
+ #  -------------------------------------------
+1>  {a}
+      ^
+ #  -------------------------------------------
+                         E
+
+      include_examples 'parse errors',
+                       'with a dictionary without a value',
+                       '{ a = ; }',
+                       <<-E
+[!] Invalid character ";" in unquoted string
+ #  -------------------------------------------
+1>  { a = ; }
+          ^
+ #  -------------------------------------------
+                         E
+
+      include_examples 'parse errors',
+                       'with an unterminated quoted string',
+                       "{\na = 'bcd\n}",
+                       <<-E
+[!] Unterminated quoted string, expected ' but never found it
+ #  -------------------------------------------
+ #  {
+2>  a = 'bcd
+         ^
+ #  }
+ #  -------------------------------------------
+                         E
+
+      include_examples 'parse errors',
+                       'with non-whitespace after the root object',
+                       'abcd a',
+                       <<-E
+[!] Found additional characters after parsing the root plist object
+ #  -------------------------------------------
+1>  abcd a
+         ^
+ #  -------------------------------------------
+                         E
+
+      include_examples 'parse errors',
+                       'when a data is unterminated',
+                       '<1234',
+                       <<-E
+[!] Data missing closing '>'
+ #  -------------------------------------------
+1>  <1234
+     ^
+ #  -------------------------------------------
+                         E
     end
   end
 end