Fix sqllogictest when the expected output starts with a whitespace

src/sqllogictest/src/parser.rs

@@ -257,8 +257,22 @@ impl<'a> Parser<'a> {
                 &EOF_REGEX
             } else {
                 &DOUBLE_LINE_REGEX
-            })?
-            .trim_start();
+            })?;
+
+        // The `split_at(&QUERY_OUTPUT_REGEX)` stopped at the end of `----`, so `output_str` usually
+        // starts with a newline, which is not actually part of the expected output. Strip off this
+        // newline.
+        output_str = if let Some(output_str_stripped) = regexp_strip_prefix(output_str, &LINE_REGEX) {
+            output_str_stripped
+        } else {
+            // There should always be a newline after `----`, because we have a lint that there is
+            // always a newline at the end of a file. However, we can still get here, when
+            // the expected output is empty, in which case the EOF_REGEX or DOUBLE_LINE_REGEX eats
+            // the newline at the end of the `----`.
+            assert!(output_str.is_empty());
+            output_str
+        };
+
         // We don't want to advance the expected output past the column names so rewriting works,
         // but need to be able to parse past them, so remember the position before possible column
         // names.
@@ -434,3 +448,16 @@ pub(crate) fn split_cols(line: &str, expected_columns: usize) -> Vec<&str> {
         line.split_whitespace().collect()
     }
 }
+
+pub fn regexp_strip_prefix<'a>(text: &'a str, regexp: &Regex) -> Option<&'a str> {
+    match regexp.find(text) {
+        Some(found) => {
+            if found.start() == 0 {
+                Some(&text[found.end()..])
+            } else {
+                None
+            }
+        }
+        None => None,
+    }
+}

test/sqllogictest/mztimestamp.slt

@@ -78,7 +78,7 @@ SELECT 1::mz_catalog.mz_timestamp
 query T
 SELECT '1970-01-02'::date::mz_timestamp
 ----
- 86400000
+86400000
 
 # Casts to timestamp[tz]. 8210266815600000 is roughly `HIGH_DATE` for `CheckedTimestamp`.
 query T

test/sqllogictest/with_mutually_recursive.slt

@@ -671,7 +671,6 @@ WITH MUTUALLY RECURSIVE
 SELECT x FROM bar
 
 ## Adapted from https://www.sqlite.org/lang_with.html#outlandish_recursive_query_examples
-## The 'x' at the beginning is to work around an sqllogictest bug.
 query T multiline
 WITH MUTUALLY RECURSIVE
   xaxis(x double) AS (VALUES(-2.0) UNION ALL SELECT x+0.05 FROM xaxis WHERE x<1.2),
@@ -689,9 +688,8 @@ WITH MUTUALLY RECURSIVE
     SELECT string_agg( substr(' .+*#', 1+least(iter/7,4), 1), '' ORDER BY cx), cy
     FROM m2 GROUP BY cy
   )
-SELECT 'x' || chr(10) || string_agg(rtrim(t), chr(10) ORDER BY cy) FROM a;
+SELECT string_agg(rtrim(t), chr(10) ORDER BY cy) FROM a;
 ----
-x
                                     ....#
                                    ..#*..
                                  ..+####+.