fix(ast/estree): Better align program span start

crates/oxc_ast/src/serialize.rs

@@ -1,12 +1,12 @@
 use cow_utils::CowUtils;
 
+use crate::ast::*;
 use oxc_ast_macros::ast_meta;
 use oxc_estree::{
     CompactJSSerializer, CompactTSSerializer, ESTree, JsonSafeString, LoneSurrogatesString,
     PrettyJSSerializer, PrettyTSSerializer, SequenceSerializer, Serializer, StructSerializer,
 };
-
-use crate::ast::*;
+use oxc_span::GetSpan;
 
 /// Main serialization methods for `Program`.
 ///
@@ -37,7 +37,16 @@ const JSON_CAPACITY_RATIO_PRETTY: usize = 80;
 
 impl Program<'_> {
     /// Serialize AST to ESTree JSON, including TypeScript fields.
-    pub fn to_estree_ts_json(&self) -> String {
+    pub fn to_estree_ts_json(&mut self) -> String {
+        // Set start span to first token of first directive or statement. This is required because
+        // unlike Acorn, TS-ESLint excludes whitespace and comments from the `Program` start span.
+        // See https://github.com/oxc-project/oxc/pull/10134 for more info.
+        if let Some(first_directive) = self.directives.first() {
+            self.span.start = first_directive.span.start;
+        } else if let Some(first_stmt) = self.body.first() {
+            self.span.start = first_stmt.span().start;
+        }
+
         let capacity = self.source_text.len() * JSON_CAPACITY_RATIO_COMPACT;
         let mut serializer = CompactTSSerializer::with_capacity(capacity);
         self.serialize(&mut serializer);
@@ -53,7 +62,16 @@ impl Program<'_> {
     }
 
     /// Serialize AST to pretty-printed ESTree JSON, including TypeScript fields.
-    pub fn to_pretty_estree_ts_json(&self) -> String {
+    pub fn to_pretty_estree_ts_json(&mut self) -> String {
+        // Set start span to first token of first directive or statement. This is required because
+        // unlike Acorn, TS-ESLint excludes whitespace and comments from the `Program` start span.
+        // See https://github.com/oxc-project/oxc/pull/10134 for more info.
+        if let Some(first_directive) = self.directives.first() {
+            self.span.start = first_directive.span.start;
+        } else if let Some(first_stmt) = self.body.first() {
+            self.span.start = first_stmt.span().start;
+        }
+
         let capacity = self.source_text.len() * JSON_CAPACITY_RATIO_PRETTY;
         let mut serializer = PrettyTSSerializer::with_capacity(capacity);
         self.serialize(&mut serializer);