Make it possible to generate code better in structures with snippets (#…

…1146)

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> [!IMPORTANT]
> Add support for backtick strings in JSON parser and include
comprehensive test cases for various string formats.
> 
>   - **Behavior**:
> - Add `BacktickString` variant to `JsonCollection` in
`json_collection.rs`.
> - Update `JsonParseState` in `json_parse_state.rs` to handle
`BacktickString` during parsing.
>   - **Tests**:
> - Add `test_code.rs` with test cases for `BacktickString`, including
handling of unescaped newlines and quotes.
> - Ensure existing string formats (single, double, triple quotes) are
tested for similar cases.
> 
> <sup>This description was created by </sup>[<img alt="Ellipsis"
src="https://img.shields.io/badge/Ellipsis-blue?color=175173">](https://www.ellipsis.dev?ref=BoundaryML%2Fbaml&utm_source=github&utm_medium=referral)<sup>
for c98e049. It will automatically
update as commits are pushed.</sup>

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engine/baml-lib/jsonish/src/jsonish/parser/fixing_parser/json_collection.rs

@@ -10,6 +10,7 @@ pub enum JsonCollection {
     QuotedString(String),
     TripleQuotedString(String),
     SingleQuotedString(String),
+    BacktickString(String),
     // Handles numbers, booleans, null, and unquoted strings
     UnquotedString(String),
     // Starting with // or #
@@ -25,6 +26,7 @@ impl JsonCollection {
             JsonCollection::Array(_) => "Array",
             JsonCollection::QuotedString(_) => "String",
             JsonCollection::SingleQuotedString(_) => "String",
+            JsonCollection::BacktickString(_) => "String",
             JsonCollection::TripleQuotedString(_) => "TripleQuotedString",
             JsonCollection::UnquotedString(_) => "UnquotedString",
             JsonCollection::TrailingComment(_) => "Comment",
@@ -49,6 +51,7 @@ impl From<JsonCollection> for Option<Value> {
             JsonCollection::QuotedString(s) => Value::String(s),
             JsonCollection::TripleQuotedString(s) => Value::String(s),
             JsonCollection::SingleQuotedString(s) => Value::String(s),
+            JsonCollection::BacktickString(s) => Value::String(s),
             JsonCollection::UnquotedString(s) => {
                 let s = s.trim();
                 if s == "true" {

engine/baml-lib/jsonish/src/jsonish/parser/fixing_parser/json_parse_state.rs

@@ -74,6 +74,7 @@ impl JsonParseState {
             | JsonCollection::TripleQuotedString(s)
             | JsonCollection::BlockComment(s)
             | JsonCollection::SingleQuotedString(s)
+            | JsonCollection::BacktickString(s)
             | JsonCollection::UnquotedString(s)
             | JsonCollection::TrailingComment(s) => {
                 // println!("Consuming: {s} + {:?}", token);
@@ -484,6 +485,22 @@ impl JsonParseState {
                         _ => self.consume(token),
                     }
                 }
+                JsonCollection::BacktickString(_) => {
+                    // We could be expecting:
+                    // - A closing backtick
+                    // - A character
+                    match token {
+                        '`' => {
+                            if self.should_close_string(next, '`') {
+                                self.complete_collection();
+                                Ok(0)
+                            } else {
+                                self.consume(token)
+                            }
+                        }
+                        _ => self.consume(token),
+                    }
+                }
                 JsonCollection::SingleQuotedString(_) => {
                     // We could be expecting:
                     // - A closing quote
@@ -599,6 +616,12 @@ impl JsonParseState {
                     Default::default(),
                 ));
             }
+            '`' => {
+                self.collection_stack.push((
+                    JsonCollection::BacktickString(String::new()),
+                    Default::default(),
+                ));
+            }
             '/' => {
                 // Could be a comment
                 match next.peek() {

engine/baml-lib/jsonish/src/tests/mod.rs

@@ -7,6 +7,7 @@ pub mod macros;
 mod test_basics;
 mod test_class;
 mod test_class_2;
+mod test_code;
 mod test_constraints;
 mod test_enum;
 mod test_lists;