fix: Allow an off-by-one in Token matching (#15)

As some minifiers do not output exact tokens but include a leading whitespace.

Author: Swatinem

src/name_resolver.rs

@@ -32,9 +32,11 @@ impl<'a, T: AsRef<str>> NameResolver<'a, T> {
         let token = self
             .sourcemap
             .lookup_token(source_position.line, source_position.column)?;
-        let is_exact_match = token.get_dst() == (source_position.line, source_position.column);
 
-        if is_exact_match {
+        let is_exactish_match = token.get_dst_line() == source_position.line
+            && token.get_dst_col() >= source_position.column - 1;
+
+        if is_exactish_match {
             token.get_name()
         } else {
             None

tests/fixtures/off-by-one/README.md

@@ -0,0 +1,10 @@
+This SourceMap has an "off by one" problem.
+
+Minified positions for tokens use the preceding tokens end rather than
+accounting for whitespace and having an exact start.
+
+This looks a little bit like so:
+
+`var| a|=...|function| b()`
+... but should rather be (with exact matches):
+`var |a|=...|function |b()`

tests/fixtures/off-by-one/test.map

@@ -205,7 +205,7 @@ fn parses_large_vendors() {
 }
 
 #[test]
-fn should_only_resolve_exact() {
+fn should_not_resolve_mismatch() {
     let minified = fixture("prototype-chain/minified.js");
     let map = fixture("prototype-chain/minified.js.map");
 
@@ -218,3 +218,17 @@ fn should_only_resolve_exact() {
 
     assert_eq!(resolved_scopes[1].2, Some("Foo.prototype.bar".into()));
 }
+
+#[test]
+fn should_resolve_exactish() {
+    let minified = fixture("off-by-one/test.min.js");
+    let map = fixture("off-by-one/test.map");
+
+    let scopes = extract_scope_names(&minified).unwrap();
+
+    let resolved_scopes = resolve_original_scopes(&minified, &map, scopes);
+
+    assert_eq!(resolved_scopes[2].2, Some("onFailure".into()));
+    assert_eq!(resolved_scopes[3].2, Some("invoke".into()));
+    assert_eq!(resolved_scopes[4].2, Some("test".into()));
+}