Add support for nullish values in points

Closes GH-4.

Reviewed-by: Christian Murphy <[email protected]>
Reviewed-by: Titus Wormer <[email protected]>

Author: remcohaszing

lib/index.js

@@ -15,8 +15,8 @@
  */
 export function fromPoint(point) {
   return {
-    character: point.column - 1,
-    line: point.line - 1
+    character: point.column ? point.column - 1 : 0,
+    line: point.line ? point.line - 1 : 0
   }
 }
 

test/index.js

@@ -17,6 +17,19 @@ test('fromPoint', async () => {
     {line: 42, character: 99},
     'should convert unist points to LSP positions'
   )
+
+  assert.deepEqual(
+    fromPoint({line: 0, column: 0}),
+    {line: 0, character: 0},
+    'should convert unist points with zero values'
+  )
+
+  assert.deepEqual(
+    // @ts-expect-error We test invalid user input here.
+    fromPoint({line: null, column: null}),
+    {line: 0, character: 0},
+    'should convert unist points with null values'
+  )
 })
 
 test('toPoint', async () => {