fix(editor): skip duplicate table aliases

apps/desktop/src/lib/sql/sqlCompletion.ts

@@ -1158,6 +1158,7 @@ export interface SqlCompletionContext {
   deleteTarget?: { table: string; schema?: string };
   oracleTableFunctionContext?: boolean;
   autoAliasTableCompletions: boolean;
+  tableAliasAfterCursor?: boolean;
   contextKind: SqlCompletionContextKind;
 }
 
@@ -1286,7 +1287,7 @@ class SqlCompletionProvider {
     }
 
     const emptyTableNameCompletion = !context.prefix && (context.suggestTables || context.exclusiveTableSuggestions);
-    if (!pendingJoinKeyword && !emptyTableNameCompletion && context.referencedTables.length > 0 && !context.suggestColumns && !context.insertTable) {
+    if (!pendingJoinKeyword && !emptyTableNameCompletion && !context.tableAliasAfterCursor && context.referencedTables.length > 0 && !context.suggestColumns && !context.insertTable) {
       this.items.push(...buildAliasItems(context, this.databaseType));
     }
 
@@ -1617,6 +1618,50 @@ function isCallRoutineContext(beforeToken: string): boolean {
   return /\bcall\s+(?:[A-Za-z_][\w$]*\.)?$/i.test(beforeToken) || /\bcall\s+(?:[A-Za-z_][\w$]*\.)?[A-Za-z_][\w$]*$/i.test(beforeToken);
 }
 
+const SQL_IDENTIFIER_CONTINUE_CHAR = /[$_\u200c\u200d\p{ID_Continue}]/u;
+
+function hasTableAliasAfterCursor(sql: string, cursor: number): boolean {
+  if (hasAliasMarkerAt(sql, cursor, false)) return true;
+  let pos = cursor;
+  while (pos < sql.length) {
+    const codePoint = sql.codePointAt(pos);
+    if (codePoint === undefined) break;
+    const char = String.fromCodePoint(codePoint);
+    if (char !== "." && !SQL_IDENTIFIER_CONTINUE_CHAR.test(char)) break;
+    // Advance by the full code point so supplementary Unicode identifiers
+    // do not leave the scan between UTF-16 surrogate halves.
+    pos += char.length;
+  }
+  if (sql[pos] === '"' || sql[pos] === "`" || sql[pos] === "]") pos++;
+  return hasAliasMarkerAt(sql, pos, true);
+}
+
+function hasAliasMarkerAt(sql: string, pos: number, allowImplicitAlias: boolean): boolean {
+  const following = sql.slice(skipSqlWhitespaceAndComments(sql, pos));
+  if (/^as\b/i.test(following)) return true;
+  if (/^(?:"[^"]+"|`[^`]+`|\[[^\]]+\])/.test(following)) return true;
+  if (!allowImplicitAlias) return false;
+  const implicitAlias = /^([A-Za-z_][\w$]*)/.exec(following)?.[1]?.toLowerCase();
+  return !!implicitAlias && !isUnsafeSqlAlias(implicitAlias);
+}
+
+function skipSqlWhitespaceAndComments(sql: string, pos: number): number {
+  for (;;) {
+    while (pos < sql.length && /\s/.test(sql[pos])) pos++;
+    if (sql.startsWith("--", pos)) {
+      const newline = sql.indexOf("\n", pos + 2);
+      if (newline === -1) return sql.length;
+      pos = newline + 1;
+    } else if (sql.startsWith("/*", pos)) {
+      const end = sql.indexOf("*/", pos + 2);
+      if (end === -1) return sql.length;
+      pos = end + 2;
+    } else {
+      return pos;
+    }
+  }
+}
+
 export function getSqlCompletionContext(sql: string, cursor: number): SqlCompletionContext {
   // Extract the full statement at cursor position for referenced tables
   const fullStatement = extractStatementAt(sql, cursor);
@@ -1664,7 +1709,8 @@ export function getSqlCompletionContext(sql: string, cursor: number): SqlComplet
 
   const afterTableTrigger = TABLE_TRIGGER_KEYWORDS.has(lastWord) || (JOIN_MODIFIERS.has(lastWord) && isFollowedByJoin(beforeToken)) || isInTableListContext(beforeToken);
   const exclusiveTableSuggestions = EXCLUSIVE_TABLE_TRIGGER_KEYWORDS.has(lastWord) || (JOIN_MODIFIERS.has(lastWord) && isFollowedByJoin(beforeToken)) || isInTableListContext(beforeToken);
-  const autoAliasTableCompletions = lastWord === "from" || lastWord === "join" || (JOIN_MODIFIERS.has(lastWord) && isFollowedByJoin(beforeToken)) || isInTableListContext(beforeToken);
+  const tableAliasAfterCursor = hasTableAliasAfterCursor(sql, cursor);
+  const autoAliasTableCompletions = (lastWord === "from" || lastWord === "join" || (JOIN_MODIFIERS.has(lastWord) && isFollowedByJoin(beforeToken)) || isInTableListContext(beforeToken)) && !tableAliasAfterCursor;
   const exclusiveColumnSuggestions = !!qualifier && !exclusiveTableSuggestions && !insertInfo;
   const activePrefixIsCte = cteDefs.some((cte) => normalizeIdentifierPart(cte.name) === normalizeIdentifierPart(prefix));
   if (exclusiveTableSuggestions && prefix && !activePrefixIsCte && referencedTables.length > 1) {
@@ -1728,6 +1774,7 @@ export function getSqlCompletionContext(sql: string, cursor: number): SqlComplet
     deleteTarget: deleteInfo?.target,
     oracleTableFunctionContext,
     autoAliasTableCompletions,
+    tableAliasAfterCursor,
     contextKind,
   };
 }

packages/app-tests/sqlCompletion.test.ts

@@ -2009,6 +2009,59 @@ test("automatic table aliases avoid reserved words", () => {
   assert.equal(tableItem!.apply, "orders AS ord");
 });
 
+test("automatic table aliases respect text after the cursor", () => {
+  const cases: Array<[string, number, string]> = [
+    ["select * from ord AS o", "select * from ord".length, "orders"],
+    ["select * from ord o", "select * from ord".length, "orders"],
+    ["select * from ord where id = 1", "select * from ord".length, "orders AS ord"],
+    ["select * from ord", "select * from ord".length, "orders AS ord"],
+    ["select * from ord, users", "select * from ord".length, "orders AS ord"],
+    ["select * from orders AS o", "select * from or".length, "orders"],
+    ["select * from ord单 AS o", "select * from ord".length, "orders"],
+    ["select * from orde\u0301 AS o", "select * from ord".length, "orders"],
+    ["select * from ord𐐀 AS o", "select * from ord".length, "orders"],
+    ['select * from ord AS "o"', "select * from ord".length, "orders"],
+    ["select * from ord `o`", "select * from ord".length, "orders"],
+    ["select * from ord AS ", "select * from ord".length, "orders"],
+    ["select * from ord /* comment */ AS o", "select * from ord".length, "orders"],
+    ["select * from ord -- comment\n  o", "select * from ord".length, "orders"],
+    ["select * from ord\n  o", "select * from ord".length, "orders"],
+    ["select * from ord /* ; */ AS o", "select * from ord".length, "orders"],
+    ["select * from ord /* comment */ where id = 1", "select * from ord".length, "orders AS ord"],
+  ];
+
+  for (const [sql, cursor, expectedApply] of cases) {
+    const items = buildSqlCompletionItems(sql, cursor, {
+      tables,
+      columnsByTable,
+      autoAliasTables: true,
+    });
+
+    const tableItem = items.find((item) => item.type === "table" && item.label === "orders");
+    assert.ok(tableItem, `should suggest orders for ${sql}`);
+    assert.equal(tableItem!.apply, expectedApply, sql);
+  }
+});
+
+test("table alias suggestions respect text after the cursor", () => {
+  const aliasedCases: Array<[string, number]> = [
+    ["select * from orders AS o", "select * from orders ".length],
+    ['select * from orders AS "o"', "select * from orders ".length],
+    ["select * from orders AS ", "select * from orders ".length],
+    ["select * from orders /* c */ AS o", "select * from orders ".length],
+  ];
+
+  for (const [sql, cursor] of aliasedCases) {
+    const items = buildSqlCompletionItems(sql, cursor, { tables, columnsByTable });
+    const aliasItem = items.find((item) => item.type === "snippet" && item.detail === "alias for orders");
+    assert.equal(aliasItem, undefined, sql);
+  }
+
+  const items = buildSqlCompletionItems("select * from orders ", "select * from orders ".length, { tables, columnsByTable });
+  const aliasItem = items.find((item) => item.type === "snippet" && item.detail === "alias for orders");
+  assert.ok(aliasItem, "alias snippet should remain available when no alias follows");
+});
+
 test("table alias suggestions avoid SQL keywords", () => {
   const items = buildSqlCompletionItems("select * from item_file ", "select * from item_file ".length, {
     tables: [{ name: "item_file", schema: "public", type: "table" }],