Fix diagnostics ranges

Author: julienduchesne

server/diagnostics.go

@@ -153,7 +153,7 @@ func (s *server) getEvalDiags(doc *document) (diags []protocol.Diagnostic) {
 			diag.Severity = protocol.SeverityError
 		}
 
-		diag.Range = NewProtocolRange(line, col, endLine, endCol)
+		diag.Range = NewProtocolRange(line-1, col-1, endLine-1, endCol-1)
 		diags = append(diags, diag)
 	}
 
@@ -190,7 +190,7 @@ func (s *server) getLintDiags(doc *document) (diags []protocol.Diagnostic) {
 
 			diag.Message = match[9]
 
-			diag.Range = NewProtocolRange(line, col, endLine, endCol)
+			diag.Range = NewProtocolRange(line-1, col-1, endLine-1, endCol-1)
 			diags = append(diags, diag)
 		}
 	}

server/diagnostics_test.go

@@ -0,0 +1,47 @@
+package server
+
+import (
+	"testing"
+
+	"github.com/jdbaldry/go-language-server-protocol/lsp/protocol"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetLintDiags(t *testing.T) {
+	testCases := []struct {
+		name        string
+		fileContent string
+		expected    []protocol.Diagnostic
+	}{
+		{
+			name: "unused variable",
+			fileContent: `
+local unused = 'test';
+{}
+`,
+			expected: []protocol.Diagnostic{
+				{
+					Range: protocol.Range{
+						Start: protocol.Position{Line: 1, Character: 6},
+						End:   protocol.Position{Line: 1, Character: 21},
+					},
+					Severity: protocol.SeverityWarning,
+					Source:   "lint",
+					Message:  "Unused variable: unused",
+				},
+			},
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			s, fileURI := testServerWithFile(t, nil, tc.fileContent)
+			doc, err := s.cache.get(fileURI)
+			if err != nil {
+				t.Fatalf("%s: %v", errorRetrievingDocument, err)
+			}
+
+			diags := s.getLintDiags(doc)
+			assert.Equal(t, tc.expected, diags)
+		})
+	}
+}