fix: Handling situation when diagnostics contain nil range (#6729)

Author: yhakbar

internal/view/diagnostic/diagnostic.go

@@ -8,9 +8,11 @@ import (
 
 type Diagnostics []*Diagnostic
 
+// Contains reports whether diags holds a diagnostic with the same source range as find.
+// A diagnostic without a range matches nothing, not even another one without a range.
 func (diags *Diagnostics) Contains(find *Diagnostic) bool {
 	for _, diag := range *diags {
-		if find.Range != nil && find.Range.String() == diag.Range.String() {
+		if find.Range != nil && diag.Range != nil && find.Range.String() == diag.Range.String() {
 			return true
 		}
 	}

internal/view/diagnostic/diagnostic_test.go

@@ -0,0 +1,83 @@
+package diagnostic_test
+
+import (
+	"testing"
+
+	"github.com/gruntwork-io/terragrunt/internal/view/diagnostic"
+	"github.com/hashicorp/hcl/v2"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func rangeOnLine(line int) *diagnostic.Range {
+	return &diagnostic.Range{
+		Filename: "terragrunt.hcl",
+		Start:    diagnostic.Pos{Line: line, Column: 1, Byte: 0},
+		End:      diagnostic.Pos{Line: line, Column: 5, Byte: 4},
+	}
+}
+
+func TestDiagnosticsContains(t *testing.T) {
+	t.Parallel()
+
+	tc := []struct {
+		find     *diagnostic.Diagnostic
+		name     string
+		stored   diagnostic.Diagnostics
+		expected bool
+	}{
+		{
+			name:     "same range",
+			stored:   diagnostic.Diagnostics{{Range: rangeOnLine(1)}},
+			find:     &diagnostic.Diagnostic{Range: rangeOnLine(1)},
+			expected: true,
+		},
+		{
+			name:     "different range",
+			stored:   diagnostic.Diagnostics{{Range: rangeOnLine(1)}},
+			find:     &diagnostic.Diagnostic{Range: rangeOnLine(2)},
+			expected: false,
+		},
+		{
+			name:     "stored diagnostic without a range is skipped",
+			stored:   diagnostic.Diagnostics{{Summary: "no subject"}, {Range: rangeOnLine(1)}},
+			find:     &diagnostic.Diagnostic{Range: rangeOnLine(1)},
+			expected: true,
+		},
+		{
+			name:     "searched diagnostic without a range",
+			stored:   diagnostic.Diagnostics{{Range: rangeOnLine(1)}},
+			find:     &diagnostic.Diagnostic{Summary: "no subject"},
+			expected: false,
+		},
+		{
+			name:     "neither has a range",
+			stored:   diagnostic.Diagnostics{{Summary: "no subject"}},
+			find:     &diagnostic.Diagnostic{Summary: "no subject"},
+			expected: false,
+		},
+	}
+
+	for _, tt := range tc {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			assert.Equal(t, tt.expected, tt.stored.Contains(tt.find))
+		})
+	}
+}
+
+func TestDiagnosticsContainsDiagnosticWithoutSubject(t *testing.T) {
+	t.Parallel()
+
+	withoutSubject := diagnostic.NewDiagnostic(nil, &hcl.Diagnostic{
+		Severity: hcl.DiagError,
+		Summary:  "Multiple terraform blocks",
+	})
+	require.Nil(t, withoutSubject.Range)
+
+	diags := diagnostic.Diagnostics{withoutSubject}
+
+	assert.False(t, diags.Contains(withoutSubject))
+	assert.False(t, diags.Contains(&diagnostic.Diagnostic{Range: rangeOnLine(1)}))
+}