parser: validated unicode uescape character

crates/squawk_syntax/src/snapshots/squawk_syntax__test__unicode_escape_ident_validation.snap

@@ -2,7 +2,7 @@
 source: crates/squawk_syntax/src/test.rs
 input_file: crates/squawk_syntax/test_data/validation/unicode_escape_ident.sql
 ---
-SOURCE_FILE@0..243
+SOURCE_FILE@0..425
   COMMENT@0..5 "-- ok"
   WHITESPACE@5..6 "\n"
   SELECT@6..32
@@ -113,6 +113,90 @@ SOURCE_FILE@0..243
             IDENT@235..241 "U&\" \\\""
   SEMICOLON@241..242 ";"
   WHITESPACE@242..243 "\n"
+  SELECT@243..270
+    SELECT_CLAUSE@243..270
+      SELECT_KW@243..249 "select"
+      WHITESPACE@249..250 " "
+      TARGET_LIST@250..270
+        TARGET@250..270
+          NAME_REF@250..270
+            IDENT@250..259 "U&\"error\""
+            WHITESPACE@259..260 " "
+            UESCAPE_KW@260..267 "UESCAPE"
+            WHITESPACE@267..268 " "
+            STRING@268..270 "''"
+  SEMICOLON@270..271 ";"
+  WHITESPACE@271..272 "\n"
+  SELECT@272..300
+    SELECT_CLAUSE@272..300
+      SELECT_KW@272..278 "select"
+      WHITESPACE@278..279 " "
+      TARGET_LIST@279..300
+        TARGET@279..300
+          NAME_REF@279..300
+            IDENT@279..288 "U&\"error\""
+            WHITESPACE@288..289 " "
+            UESCAPE_KW@289..296 "UESCAPE"
+            WHITESPACE@296..297 " "
+            STRING@297..300 "' '"
+  SEMICOLON@300..301 ";"
+  WHITESPACE@301..302 "\n"
+  SELECT@302..330
+    SELECT_CLAUSE@302..330
+      SELECT_KW@302..308 "select"
+      WHITESPACE@308..309 " "
+      TARGET_LIST@309..330
+        TARGET@309..330
+          NAME_REF@309..330
+            IDENT@309..318 "U&\"error\""
+            WHITESPACE@318..319 " "
+            UESCAPE_KW@319..326 "UESCAPE"
+            WHITESPACE@326..327 " "
+            STRING@327..330 "'+'"
+  SEMICOLON@330..331 ";"
+  WHITESPACE@331..332 "\n"
+  SELECT@332..360
+    SELECT_CLAUSE@332..360
+      SELECT_KW@332..338 "select"
+      WHITESPACE@338..339 " "
+      TARGET_LIST@339..360
+        TARGET@339..360
+          NAME_REF@339..360
+            IDENT@339..348 "U&\"error\""
+            WHITESPACE@348..349 " "
+            UESCAPE_KW@349..356 "UESCAPE"
+            WHITESPACE@356..357 " "
+            STRING@357..360 "'A'"
+  SEMICOLON@360..361 ";"
+  WHITESPACE@361..362 "\n"
+  SELECT@362..391
+    SELECT_CLAUSE@362..391
+      SELECT_KW@362..368 "select"
+      WHITESPACE@368..369 " "
+      TARGET_LIST@369..391
+        TARGET@369..391
+          NAME_REF@369..391
+            IDENT@369..378 "U&\"error\""
+            WHITESPACE@378..379 " "
+            UESCAPE_KW@379..386 "UESCAPE"
+            WHITESPACE@386..387 " "
+            STRING@387..391 "'é'"
+  SEMICOLON@391..392 ";"
+  WHITESPACE@392..393 "\n"
+  SELECT@393..423
+    SELECT_CLAUSE@393..423
+      SELECT_KW@393..399 "select"
+      WHITESPACE@399..400 " "
+      TARGET_LIST@400..423
+        TARGET@400..423
+          NAME_REF@400..423
+            IDENT@400..409 "U&\"error\""
+            WHITESPACE@409..410 " "
+            UESCAPE_KW@410..417 "UESCAPE"
+            WHITESPACE@417..418 " "
+            STRING@418..423 "'foo'"
+  SEMICOLON@423..424 ";"
+  WHITESPACE@424..425 "\n"
 
 error[syntax-error]: Unicode escape requires 4 hex digits: \XXXX
   ╭▸ 
@@ -134,3 +218,27 @@ error[syntax-error]: Invalid Unicode escape sequence
    ╭▸ 
 12 │ select U&" \";
    ╰╴       ━━━━━━
+error[syntax-error]: Invalid unicode escape character
+   ╭▸ 
+13 │ select U&"error" UESCAPE '';
+   ╰╴                         ━━
+error[syntax-error]: Invalid unicode escape character
+   ╭▸ 
+14 │ select U&"error" UESCAPE ' ';
+   ╰╴                         ━━━
+error[syntax-error]: Invalid unicode escape character
+   ╭▸ 
+15 │ select U&"error" UESCAPE '+';
+   ╰╴                         ━━━
+error[syntax-error]: Invalid unicode escape character
+   ╭▸ 
+16 │ select U&"error" UESCAPE 'A';
+   ╰╴                         ━━━
+error[syntax-error]: Invalid unicode escape character
+   ╭▸ 
+17 │ select U&"error" UESCAPE 'é';
+   ╰╴                         ━━━
+error[syntax-error]: Invalid unicode escape character
+   ╭▸ 
+18 │ select U&"error" UESCAPE 'foo';
+   ╰╴                         ━━━━━

crates/squawk_syntax/src/snapshots/squawk_syntax__test__unicode_escape_string_validation.snap

@@ -2,7 +2,7 @@
 source: crates/squawk_syntax/src/test.rs
 input_file: crates/squawk_syntax/test_data/validation/unicode_escape_string.sql
 ---
-SOURCE_FILE@0..241
+SOURCE_FILE@0..423
   COMMENT@0..5 "-- ok"
   WHITESPACE@5..6 "\n"
   SELECT@6..30
@@ -113,6 +113,90 @@ SOURCE_FILE@0..241
             UNICODE_ESC_STRING@233..239 "U&' \\'"
   SEMICOLON@239..240 ";"
   WHITESPACE@240..241 "\n"
+  SELECT@241..268
+    SELECT_CLAUSE@241..268
+      SELECT_KW@241..247 "select"
+      WHITESPACE@247..248 " "
+      TARGET_LIST@248..268
+        TARGET@248..268
+          LITERAL@248..268
+            UNICODE_ESC_STRING@248..257 "U&'error'"
+            WHITESPACE@257..258 " "
+            UESCAPE_KW@258..265 "UESCAPE"
+            WHITESPACE@265..266 " "
+            STRING@266..268 "''"
+  SEMICOLON@268..269 ";"
+  WHITESPACE@269..270 "\n"
+  SELECT@270..298
+    SELECT_CLAUSE@270..298
+      SELECT_KW@270..276 "select"
+      WHITESPACE@276..277 " "
+      TARGET_LIST@277..298
+        TARGET@277..298
+          LITERAL@277..298
+            UNICODE_ESC_STRING@277..286 "U&'error'"
+            WHITESPACE@286..287 " "
+            UESCAPE_KW@287..294 "UESCAPE"
+            WHITESPACE@294..295 " "
+            STRING@295..298 "' '"
+  SEMICOLON@298..299 ";"
+  WHITESPACE@299..300 "\n"
+  SELECT@300..328
+    SELECT_CLAUSE@300..328
+      SELECT_KW@300..306 "select"
+      WHITESPACE@306..307 " "
+      TARGET_LIST@307..328
+        TARGET@307..328
+          LITERAL@307..328
+            UNICODE_ESC_STRING@307..316 "U&'error'"
+            WHITESPACE@316..317 " "
+            UESCAPE_KW@317..324 "UESCAPE"
+            WHITESPACE@324..325 " "
+            STRING@325..328 "'+'"
+  SEMICOLON@328..329 ";"
+  WHITESPACE@329..330 "\n"
+  SELECT@330..358
+    SELECT_CLAUSE@330..358
+      SELECT_KW@330..336 "select"
+      WHITESPACE@336..337 " "
+      TARGET_LIST@337..358
+        TARGET@337..358
+          LITERAL@337..358
+            UNICODE_ESC_STRING@337..346 "U&'error'"
+            WHITESPACE@346..347 " "
+            UESCAPE_KW@347..354 "UESCAPE"
+            WHITESPACE@354..355 " "
+            STRING@355..358 "'A'"
+  SEMICOLON@358..359 ";"
+  WHITESPACE@359..360 "\n"
+  SELECT@360..389
+    SELECT_CLAUSE@360..389
+      SELECT_KW@360..366 "select"
+      WHITESPACE@366..367 " "
+      TARGET_LIST@367..389
+        TARGET@367..389
+          LITERAL@367..389
+            UNICODE_ESC_STRING@367..376 "U&'error'"
+            WHITESPACE@376..377 " "
+            UESCAPE_KW@377..384 "UESCAPE"
+            WHITESPACE@384..385 " "
+            STRING@385..389 "'é'"
+  SEMICOLON@389..390 ";"
+  WHITESPACE@390..391 "\n"
+  SELECT@391..421
+    SELECT_CLAUSE@391..421
+      SELECT_KW@391..397 "select"
+      WHITESPACE@397..398 " "
+      TARGET_LIST@398..421
+        TARGET@398..421
+          LITERAL@398..421
+            UNICODE_ESC_STRING@398..407 "U&'error'"
+            WHITESPACE@407..408 " "
+            UESCAPE_KW@408..415 "UESCAPE"
+            WHITESPACE@415..416 " "
+            STRING@416..421 "'foo'"
+  SEMICOLON@421..422 ";"
+  WHITESPACE@422..423 "\n"
 
 error[syntax-error]: Unicode escape requires 4 hex digits: \XXXX
   ╭▸ 
@@ -134,3 +218,27 @@ error[syntax-error]: Invalid Unicode escape sequence
    ╭▸ 
 12 │ select U&' \';
    ╰╴       ━━━━━━
+error[syntax-error]: Invalid unicode escape character
+   ╭▸ 
+13 │ select U&'error' UESCAPE '';
+   ╰╴                         ━━
+error[syntax-error]: Invalid unicode escape character
+   ╭▸ 
+14 │ select U&'error' UESCAPE ' ';
+   ╰╴                         ━━━
+error[syntax-error]: Invalid unicode escape character
+   ╭▸ 
+15 │ select U&'error' UESCAPE '+';
+   ╰╴                         ━━━
+error[syntax-error]: Invalid unicode escape character
+   ╭▸ 
+16 │ select U&'error' UESCAPE 'A';
+   ╰╴                         ━━━
+error[syntax-error]: Invalid unicode escape character
+   ╭▸ 
+17 │ select U&'error' UESCAPE 'é';
+   ╰╴                         ━━━
+error[syntax-error]: Invalid unicode escape character
+   ╭▸ 
+18 │ select U&'error' UESCAPE 'foo';
+   ╰╴                         ━━━━━

crates/squawk_syntax/src/validation.rs

@@ -192,7 +192,15 @@ fn validate_unicode_esc_string(lit: &ast::Literal) -> Option<SyntaxError> {
             UNICODE_ESC_STRING => unicode_esc = Some(token),
             UESCAPE_KW => seen_uescape = true,
             STRING if seen_uescape => {
-                escape_char = uescape_char(&token).unwrap_or(escape_char);
+                escape_char = match uescape_char(&token) {
+                    Some(ch) => ch,
+                    None => {
+                        return Some(SyntaxError::new(
+                            "Invalid unicode escape character",
+                            token.text_range(),
+                        ));
+                    }
+                };
                 break;
             }
             _ => (),
@@ -224,7 +232,15 @@ fn validate_unicode_esc_ident(token: &SyntaxToken) -> Option<SyntaxError> {
             UESCAPE_KW => seen_uescape = true,
             STRING if seen_uescape => {
                 if let Some(string_token) = element.as_token() {
-                    escape_char = uescape_char(string_token).unwrap_or(escape_char);
+                    escape_char = match uescape_char(string_token) {
+                        Some(ch) => ch,
+                        None => {
+                            return Some(SyntaxError::new(
+                                "Invalid unicode escape character",
+                                string_token.text_range(),
+                            ));
+                        }
+                    };
                 }
                 break;
             }
@@ -237,14 +253,25 @@ fn validate_unicode_esc_ident(token: &SyntaxToken) -> Option<SyntaxError> {
     Some(SyntaxError::new(err.to_string(), token.text_range()))
 }
 
+// https://github.com/postgres/postgres/blob/228a1f9542792c6533ef74c2e7aefad0da1d9a7a/src/backend/parser/parser.c#L350
+const fn is_valid_uescape_char(byte: u8) -> bool {
+    !byte.is_ascii_hexdigit()
+        && byte != b'+'
+        && byte != b'\''
+        && byte != b'"'
+        && !matches!(
+            byte,
+            b' ' | b'\t' | b'\n' | b'\r' | /* b'\v' */ 0x0B | /* b'\f' */ 0x0C
+        )
+}
+
 fn uescape_char(string_token: &SyntaxToken) -> Option<char> {
     let text = string_token.text();
     let inner = text.strip_prefix('\'')?.strip_suffix('\'')?;
-    let mut chars = inner.chars();
-    match (chars.next(), chars.next()) {
-        (Some(c), None) => Some(c),
-        _ => None,
-    }
+    let &[byte] = inner.as_bytes() else {
+        return None;
+    };
+    is_valid_uescape_char(byte).then(|| char::from(byte))
 }
 
 enum UnicodeEscapeKind {

crates/squawk_syntax/test_data/validation/unicode_escape_ident.sql

@@ -10,3 +10,9 @@ select U&"\+0061";
 select U&"wrong: \06" UESCAPE '\';
 select U&"wrong: !061" UESCAPE '!';
 select U&" \";
+select U&"error" UESCAPE '';
+select U&"error" UESCAPE ' ';
+select U&"error" UESCAPE '+';
+select U&"error" UESCAPE 'A';
+select U&"error" UESCAPE 'é';
+select U&"error" UESCAPE 'foo';

crates/squawk_syntax/test_data/validation/unicode_escape_string.sql

@@ -10,3 +10,9 @@ select U&'\+0061';
 select U&'wrong: \06' UESCAPE '\';
 select U&'wrong: !061' UESCAPE '!';
 select U&' \';
+select U&'error' UESCAPE '';
+select U&'error' UESCAPE ' ';
+select U&'error' UESCAPE '+';
+select U&'error' UESCAPE 'A';
+select U&'error' UESCAPE 'é';
+select U&'error' UESCAPE 'foo';

crates/xtask/src/sync_pg.rs

@@ -51,6 +51,7 @@ const IGNORED_LINES: &[&str] = &[
     "CREATE SUBSCRIPTION regress_testsub CONNECTION 'foo';",
     "CREATE SUBSCRIPTION regress_testsub PUBLICATION foo;",
     "SELECT U&'wrong: +0061' UESCAPE +;",
+    "SELECT U&'wrong: +0061' UESCAPE '+';",
     "CREATE STATISTICS tst;",
     "CREATE STATISTICS tst ON a, b;",
     "CREATE STATISTICS tst ON a FROM (VALUES (x)) AS foo;",

postgres/regression_suite/strings.sql

@@ -27,7 +27,7 @@ SELECT 'tricky' AS U&"\" UESCAPE '!';
 -- SELECT U&'wrong: \061';
 -- SELECT U&'wrong: \+0061';
 -- SELECT U&'wrong: +0061' UESCAPE +;
-SELECT U&'wrong: +0061' UESCAPE '+';
+-- SELECT U&'wrong: +0061' UESCAPE '+';
 
 -- SELECT U&'wrong: \db99';
 -- SELECT U&'wrong: \db99xy';