fix: autocomplete table names after FROM/JOIN keywords (#20)

Table names were not being suggested when the cursor was positioned
right after FROM or JOIN keywords with no table typed yet. This adds
detection for cursor position after these keywords using the parsed
FROM clause's `after` field.

Supports all JOIN types: INNER, LEFT, RIGHT, FULL, FULL OUTER, CROSS,
NATURAL, and plain JOIN.

Author: Artmann

packages/server/src/complete/complete.ts

@@ -111,7 +111,7 @@ class Completer {
           // Incomplete sub query 'SELECT sub FROM (SELECT e. FROM employees e) sub'
           this.addCandidatesForIncompleteSubquery(fromNodeOnCursor)
         } else {
-          this.addCandidatesForSelectQuery(e, fromNodes)
+          this.addCandidatesForSelectQuery(e, fromNodes, parsedFromClause)
           const expectedLiteralNodes =
             e.expected?.filter(
               (v): v is ExpectedLiteralNode => v.type === 'literal'
@@ -239,7 +239,11 @@ class Completer {
     this.addCandidatesForTables(this.schema.tables, false)
   }
 
-  addCandidatesForSelectQuery(e: ParseError, fromNodes: FromTableNode[]) {
+  addCandidatesForSelectQuery(
+    e: ParseError,
+    fromNodes: FromTableNode[],
+    parsedFromClause: FromClauseParserResult
+  ) {
     const subqueryTables = createTablesFromFromNodes(fromNodes)
     const schemaAndSubqueries = this.schema.tables.concat(subqueryTables)
     this.addCandidatesForSelectStar(fromNodes, schemaAndSubqueries)
@@ -263,8 +267,19 @@ class Completer {
       isPosInLocation(tableNode.location, this.pos)
     )
     const isCursorInsideFromClause = fromNodesContainingCursor.length > 0
-    if (isCursorInsideFromClause) {
-      // only add table candidates if the cursor is inside a FROM clause or JOIN clause, etc.
+
+    // Check if cursor is right after FROM keyword (no table typed yet)
+    const afterFromClause = parsedFromClause.after?.trim().toUpperCase() || ''
+    const isCursorAfterFromKeyword =
+      afterFromClause === 'FROM' ||
+      afterFromClause.startsWith('FROM ') ||
+      /^(INNER |LEFT |RIGHT |FULL |FULL OUTER |CROSS |NATURAL |OUTER )?JOIN( |$)/.test(
+        afterFromClause
+      )
+
+    if (isCursorInsideFromClause || isCursorAfterFromKeyword) {
+      // add table candidates if the cursor is inside a FROM clause, JOIN clause,
+      // or right after FROM/JOIN keyword waiting for a table name
       this.addCandidatesForTables(schemaAndSubqueries, true)
     }
 

packages/server/test/complete.test.ts

@@ -241,6 +241,24 @@ describe('From clause', () => {
     expect(result.candidates[0].insertText).toEqual('TABLE1')
   })
 
+  test('from clause: complete TableName after FROM keyword with space', () => {
+    const result = complete(
+      'SELECT * FROM ',
+      { line: 0, column: 14 },
+      SIMPLE_SCHEMA
+    )
+    expect(result.candidates.map((v) => v.label)).toContain('TABLE1')
+  })
+
+  test('from clause: complete TableName after FROM keyword with space:multi line', () => {
+    const result = complete(
+      'SELECT *\nFROM ',
+      { line: 1, column: 5 },
+      SIMPLE_SCHEMA
+    )
+    expect(result.candidates.map((v) => v.label)).toContain('TABLE1')
+  })
+
   test('from clause: complete TableName:multi lines', () => {
     const result = complete(
       'SELECT TABLE1.COLUMN1\nFROM T',
@@ -277,6 +295,69 @@ describe('From clause', () => {
     )
     expect(result.candidates.map((v) => v.label)).toContain('ON')
   })
+
+  test('from clause: complete TableName after JOIN keyword with space', () => {
+    const result = complete(
+      'SELECT * FROM TABLE1 JOIN ',
+      { line: 0, column: 26 },
+      SIMPLE_SCHEMA
+    )
+    expect(result.candidates.map((v) => v.label)).toContain('TABLE1')
+  })
+
+  test('from clause: complete TableName after INNER JOIN keyword with space', () => {
+    const result = complete(
+      'SELECT * FROM TABLE1 INNER JOIN ',
+      { line: 0, column: 32 },
+      SIMPLE_SCHEMA
+    )
+    expect(result.candidates.map((v) => v.label)).toContain('TABLE1')
+  })
+
+  test('from clause: complete TableName after LEFT JOIN keyword with space', () => {
+    const result = complete(
+      'SELECT * FROM TABLE1 LEFT JOIN ',
+      { line: 0, column: 31 },
+      SIMPLE_SCHEMA
+    )
+    expect(result.candidates.map((v) => v.label)).toContain('TABLE1')
+  })
+
+  test('from clause: complete TableName after RIGHT JOIN keyword with space', () => {
+    const result = complete(
+      'SELECT * FROM TABLE1 RIGHT JOIN ',
+      { line: 0, column: 32 },
+      SIMPLE_SCHEMA
+    )
+    expect(result.candidates.map((v) => v.label)).toContain('TABLE1')
+  })
+
+  test('from clause: complete TableName after CROSS JOIN keyword with space', () => {
+    const result = complete(
+      'SELECT * FROM TABLE1 CROSS JOIN ',
+      { line: 0, column: 32 },
+      SIMPLE_SCHEMA
+    )
+    expect(result.candidates.map((v) => v.label)).toContain('TABLE1')
+  })
+
+  test('from clause: complete TableName after FULL OUTER JOIN keyword with space', () => {
+    const result = complete(
+      'SELECT * FROM TABLE1 FULL OUTER JOIN ',
+      { line: 0, column: 37 },
+      SIMPLE_SCHEMA
+    )
+    expect(result.candidates.map((v) => v.label)).toContain('TABLE1')
+  })
+
+  test('from clause: complete TableName after NATURAL JOIN keyword with space', () => {
+    const result = complete(
+      'SELECT * FROM TABLE1 NATURAL JOIN ',
+      { line: 0, column: 34 },
+      SIMPLE_SCHEMA
+    )
+    expect(result.candidates.map((v) => v.label)).toContain('TABLE1')
+  })
 })
 
 describe('Where clause', () => {