parser: improve error recovery for misplaced join clauses (#1065)

Author: sbdchd

crates/squawk_parser/src/grammar.rs

@@ -2752,6 +2752,7 @@ fn select(p: &mut Parser, m: Option<Marker>, r: &SelectRestrictions) -> Option<C
     }
     opt_from_clause(p);
     opt_where_clause(p);
+    opt_misplaced_joins(p);
     opt_group_by_clause(p);
     opt_having_clause(p);
     opt_window_clause(p);
@@ -3465,6 +3466,16 @@ fn join(p: &mut Parser<'_>) {
     m.complete(p, JOIN);
 }
 
+// Improve error recovery for wrong joins
+fn opt_misplaced_joins(p: &mut Parser<'_>) {
+    while p.at_ts(JOIN_FIRST) {
+        let m = p.start();
+        p.error("JOINs must appear before WHERE");
+        join(p);
+        m.complete(p, ERROR);
+    }
+}
+
 fn on_clause(p: &mut Parser<'_>) {
     assert!(p.at(ON_KW));
     let m = p.start();

crates/squawk_parser/tests/data/err/select.sql

@@ -90,6 +90,11 @@ select having or c != 'b';
 select from t join u on and true;
 select from t join u on or true;
 
+-- join after the where
+select * from t
+where x > 1
+join k on true;
+
 -- select end
 select
 end;

crates/squawk_parser/tests/snapshots/tests__select_err.snap

@@ -938,6 +938,51 @@ SOURCE_FILE
               TRUE_KW "true"
   SEMICOLON ";"
   WHITESPACE "\n\n"
+  COMMENT "-- join after the where"
+  WHITESPACE "\n"
+  SELECT
+    SELECT_CLAUSE
+      SELECT_KW "select"
+      WHITESPACE " "
+      TARGET_LIST
+        TARGET
+          STAR "*"
+    WHITESPACE " "
+    FROM_CLAUSE
+      FROM_KW "from"
+      WHITESPACE " "
+      FROM_ITEM
+        NAME_REF
+          IDENT "t"
+    WHITESPACE "\n"
+    WHERE_CLAUSE
+      WHERE_KW "where"
+      WHITESPACE " "
+      BIN_EXPR
+        NAME_REF
+          IDENT "x"
+        WHITESPACE " "
+        R_ANGLE ">"
+        WHITESPACE " "
+        LITERAL
+          INT_NUMBER "1"
+    WHITESPACE "\n"
+    ERROR
+      JOIN
+        JOIN_INNER
+          JOIN_KW "join"
+        WHITESPACE " "
+        FROM_ITEM
+          NAME_REF
+            IDENT "k"
+        WHITESPACE " "
+        ON_CLAUSE
+          ON_KW "on"
+          WHITESPACE " "
+          LITERAL
+            TRUE_KW "true"
+  SEMICOLON ";"
+  WHITESPACE "\n\n"
   COMMENT "-- select end"
   WHITESPACE "\n"
   SELECT
@@ -1176,31 +1221,35 @@ error[syntax-error]: expected expression but got OR_KW
    ╭▸ 
 91 │ select from t join u on or true;
    ╰╴                        ━
-error[syntax-error]: expected SEMICOLON
+error[syntax-error]: JOINs must appear before WHERE
    ╭▸ 
-94 │   select
-   │ ┏━━━━━━━┛
-95 │ ┃ end;
-   ╰╴┗━┛
+96 │ join k on true;
+   ╰╴━
 error[syntax-error]: expected SEMICOLON
    ╭▸ 
-98 │   select
+99 │   select
    │ ┏━━━━━━━┛
-99 │ ┃ analyze;
+100│ ┃ end;
    ╰╴┗━┛
 error[syntax-error]: expected SEMICOLON
     ╭▸ 
-101 │   select
+103 │   select
     │ ┏━━━━━━━┛
-102 │ ┃ analyse;
+104 │ ┃ analyze;
     ╰╴┗━┛
 error[syntax-error]: expected SEMICOLON
     ╭▸ 
 106 │   select
     │ ┏━━━━━━━┛
-107 │ ┃ with t as (select 1)
+107 │ ┃ analyse;
+    ╰╴┗━┛
+error[syntax-error]: expected SEMICOLON
+    ╭▸ 
+111 │   select
+    │ ┏━━━━━━━┛
+112 │ ┃ with t as (select 1)
     ╰╴┗━┛
 error[syntax-error]: unexpected trailing comma
     ╭▸ 
-111 │ select 1,
+116 │ select 1,
     ╰╴        ━