fix: use StringView for @json.parse

Author: tonyfettes

json/internal_types.mbt

@@ -15,12 +15,12 @@
 ///|
 priv struct ParseContext {
   mut offset : Int
-  input : String
+  input : StringView
   end_offset : Int
 }
 
 ///|
-fn ParseContext::make(input : String) -> ParseContext {
+fn ParseContext::make(input : StringView) -> ParseContext {
   { offset: 0, input, end_offset: input.length() }
 }
 

json/lex_number.mbt

@@ -149,7 +149,12 @@ fn ParseContext::lex_number_end(
   start : Int,
   end : Int,
 ) -> (Double, String?) {
-  let s = ctx.input.unsafe_substring(start~, end~)
+  let s = ctx.input
+    .data()
+    .unsafe_substring(
+      start=ctx.input.start_offset() + start,
+      end=ctx.input.start_offset() + end,
+    )
   if !s.contains(".") && !s.contains("e") && !s.contains("E") {
     // If the string does not contain a decimal point or exponent, it is likely an integer
     // We can try to parse it as an integer first

json/lex_string.mbt

@@ -18,7 +18,11 @@ fn ParseContext::lex_string(ctx : ParseContext) -> String raise ParseError {
   let mut start = ctx.offset
   fn flush(end : Int) {
     if start > 0 && end > start {
-      buf.write_substring(ctx.input, start, end - start)
+      buf.write_substring(
+        ctx.input.data(),
+        ctx.input.start_offset() + start,
+        end - start,
+      )
     }
   }
 

json/parse.mbt

@@ -23,7 +23,7 @@ pub fn valid(input : String) -> Bool {
 }
 
 ///|
-pub fn parse(input : String) -> Json raise ParseError {
+pub fn parse(input : StringView) -> Json raise ParseError {
   let ctx = ParseContext::make(input)
   let val = ctx.parse_value()
   ctx.lex_skip_whitespace()

json/utils.mbt

@@ -13,7 +13,7 @@
 // limitations under the License.
 
 ///|
-fn offset_to_position(input : String, offset : Int) -> Position {
+fn offset_to_position(input : StringView, offset : Int) -> Position {
   let mut line = 1
   let mut column = 0
   for i in 0..<offset {