Fix parsing of multiline string literals for default field values

Co-authored-by: Tomáš Drvoštěp <tomas.drvostep@gmail.com>

Author: dourouc05

src/parsing/proto_options.jl

@@ -15,9 +15,13 @@ function _parse_option_value(ps) # TODO: proper value parsing with validation
     str_val = val(readtoken(ps))
     # C-style string literals spanning multiple lines
     if nk == Tokens.STRING_LIT && nnk == Tokens.STRING_LIT
+        iob = IOBuffer()
+        write(iob, str_val)
         while peekkind(ps) == Tokens.STRING_LIT
-            str_val = string(@view(str_val[begin:end-1]), val(readtoken(ps)))
+            seek(iob, position(iob) - 1)
+            write(iob, @view(val(readtoken(ps))[begin+1:end]))
         end
+        str_val = String(take!(iob))
     end
     return has_minus ? string("-", str_val) : str_val
 end
@@ -94,4 +98,4 @@ function _parse_option!(ps::ParserState, options::Dict{String,Union{String,Dict{
         options[option_name] = _parse_option_value(ps)
     end
     return nothing
-end
+end

test/test_parser.jl

@@ -146,6 +146,26 @@ end
         @test p.definitions["A"].fields[1].type.reference_type == Parsers.MESSAGE
     end
 
+    @testset "Single nested non-empty message proto file with default value" begin
+        s, p, ctx = translate_simple_proto("message A { optional string a = 1 [ default = \"b\" ]; }")
+
+        @test haskey(p.definitions, "A")
+        @test p.definitions["A"] isa Parsers.MessageType
+        @test p.definitions["A"].fields[1].name == "a"
+        @test p.definitions["A"].fields[1].type isa Parsers.StringType
+        @test p.definitions["A"].fields[1].options["default"] == "\"b\""
+    end
+
+    @testset "Single nested non-empty message proto file with default value on several lines" begin
+        s, p, ctx = translate_simple_proto("message A { optional string a = 1 [ default = \"b;\"\n\t\"\"\n\t\"c\" ]; }")
+
+        @test haskey(p.definitions, "A")
+        @test p.definitions["A"] isa Parsers.MessageType
+        @test p.definitions["A"].fields[1].name == "a"
+        @test p.definitions["A"].fields[1].type isa Parsers.StringType
+        @test p.definitions["A"].fields[1].options["default"] == "\"b;c\""
+    end
+
     @testset "Single self-referential message proto file" begin
         s, p, ctx = translate_simple_proto("message A { optional A a = 1; }")