fix(awk): check word boundary before emitting keyword tokens (#859)

Closes #852

Author: chaliy

crates/bashkit/src/builtins/awk.rs

@@ -623,13 +623,10 @@ impl<'a> AwkParser<'a> {
     fn matches_keyword(&mut self, keyword: &str) -> bool {
         if self.input[self.pos..].starts_with(keyword) {
             let after = self.pos + keyword.len();
-            if after >= self.input.len()
-                || !self.input[after..]
-                    .chars()
-                    .next()
-                    .unwrap()
-                    .is_alphanumeric()
-            {
+            if after >= self.input.len() || {
+                let c = self.input[after..].chars().next().unwrap();
+                !c.is_alphanumeric() && c != '_'
+            } {
                 self.pos = after;
                 return true;
             }
@@ -1523,13 +1520,10 @@ impl<'a> AwkParser<'a> {
         for kw in keywords {
             if remaining.starts_with(kw) {
                 let after = self.pos + kw.len();
-                if after >= self.input.len()
-                    || !self.input[after..]
-                        .chars()
-                        .next()
-                        .unwrap()
-                        .is_alphanumeric()
-                {
+                if after >= self.input.len() || {
+                    let c = self.input[after..].chars().next().unwrap();
+                    !c.is_alphanumeric() && c != '_'
+                } {
                     return true;
                 }
             }

crates/bashkit/tests/spec_cases/awk/eval-bugs.test.sh

@@ -17,3 +17,39 @@ printf 'feat(auth): add OAuth2\n' | awk 'match($0, /^([a-z]+)\(([^)]+)\): (.*)/,
 ### expect
 feat auth add OAuth2
 ### end
+
+### awk_keyword_prefix_identifier
+# Bug #852: identifiers starting with keywords split incorrectly
+# e.g. print_sp parsed as keyword "print" + variable "_sp"
+echo test | awk 'BEGIN { print_sp=0; print_sp++; print print_sp }'
+### expect
+1
+### end
+
+### awk_keyword_prefix_identifier_printf
+# Bug #852: printf_count must not split into printf + _count
+echo test | awk 'BEGIN { printf_count=5; print printf_count }'
+### expect
+5
+### end
+
+### awk_keyword_prefix_identifier_delete
+# Bug #852: delete_flag must not split into delete + _flag
+echo test | awk 'BEGIN { delete_flag=42; print delete_flag }'
+### expect
+42
+### end
+
+### awk_keyword_prefix_identifier_return_val
+# Bug #852: return_val must not split into return + _val
+echo test | awk 'function f() { return_val=99; return return_val } BEGIN { print f() }'
+### expect
+99
+### end
+
+### awk_keyword_prefix_identifier_if_done
+# Bug #852: if_done must not split into if + _done
+echo test | awk 'BEGIN { if_done=1; while_running=2; for_each=3; print if_done, while_running, for_each }'
+### expect
+1 2 3
+### end