validate: warn if latitude is set but not longitude or vice versa

CHANGELOG.md

@@ -28,6 +28,10 @@ input.
 * `validate --required-fields` supports conditionals (`--if`, `--if-not`,
   `--or-if`, `--or-if-not`) to determine which records must have certain fields
   set.  All records are checked for data type validity, e.g. number formatting.
+* `validate` will warn if `LAT` or `LON` is set but the other one isn’t;
+  likewise for `MY_LAT`/`MY_LON`.  It’s possible to know latitude without also
+  knowing longitude, but modern technology usually gives both together, so you
+  probably had a copy-paste error.
 
 [CQ Zones](https://mapability.com/ei8ic/maps/cqzone.php) and
 [ITU Zones](https://mapability.com/ei8ic/maps/ituzone.php):

adif/spec/validate.go

@@ -358,6 +358,20 @@ func ValidateLocation(val string, f Field, ctx ValidationContext) Validation {
 	} else if !between(min, 0.0, 60.0) {
 		return errorf("%s minutes out of range in %q", f.Name, val)
 	}
+	var other string
+	switch f.Name {
+	case LatField.Name:
+		other = LonField.Name
+	case LonField.Name:
+		other = LatField.Name
+	case MyLatField.Name:
+		other = MyLonField.Name
+	case MyLonField.Name:
+		other = MyLatField.Name
+	}
+	if other != "" && ctx.FieldValue(other) == "" {
+		return warningf("%s is set but %s is not set; latitude and longitude usually come together", f.Name, other)
+	}
 	return valid()
 }
 

adif/spec/validate_test.go

@@ -15,18 +15,31 @@
 package spec
 
 import (
+	"strings"
 	"testing"
 	"time"
 )
 
 type validateTest struct {
-	field Field
-	value string
-	want  Validity
+	field  Field
+	value  string
+	want   Validity
+	others []validateTest
 }
 
 var emptyCtx = ValidationContext{FieldValue: func(name string) string { return "" }}
 
+func validateTestCtx(v validateTest) ValidationContext {
+	return ValidationContext{FieldValue: func(name string) string {
+		for _, o := range v.others {
+			if strings.EqualFold(name, o.field.Name) {
+				return o.value
+			}
+		}
+		return ""
+	}}
+}
+
 func testValidator(t *testing.T, tc validateTest, ctx ValidationContext, funcname string) {
 	t.Helper()
 	v := TypeValidators[tc.field.Type.Name]
@@ -721,18 +734,18 @@ func TestValidateLocation(t *testing.T) {
 	tests := []validateTest{
 		{field: LatField, value: "", want: Valid},
 		{field: LonField, value: "", want: Valid},
-		{field: LatField, value: "N000 00.000", want: Valid},
-		{field: LatField, value: "S000 00.000", want: Valid},
-		{field: LonField, value: "E000 00.000", want: Valid},
-		{field: LonField, value: "W000 00.000", want: Valid},
-		{field: MyLatField, value: "N001 00.000", want: Valid},
-		{field: MyLatField, value: "S090 00.000", want: Valid},
-		{field: MyLonField, value: "E009 00.000", want: Valid},
-		{field: MyLonField, value: "W180 00.000", want: Valid},
-		{field: LatField, value: "N012 34.567", want: Valid},
-		{field: LatField, value: "S023 59.999", want: Valid},
-		{field: LonField, value: "E000 00.001", want: Valid},
-		{field: LonField, value: "W120 30.050", want: Valid},
+		{field: LatField, value: "N000 00.000", want: Valid, others: []validateTest{{field: LonField, value: "E000 00.000"}}},
+		{field: LatField, value: "S000 00.000", want: Valid, others: []validateTest{{field: LonField, value: "W000 00.000"}}},
+		{field: LonField, value: "E000 00.000", want: Valid, others: []validateTest{{field: LatField, value: "N000 00.000"}}},
+		{field: LonField, value: "W000 00.000", want: Valid, others: []validateTest{{field: LatField, value: "S000 00.000"}}},
+		{field: MyLatField, value: "N001 00.000", want: Valid, others: []validateTest{{field: MyLonField, value: "W123 45.678"}}},
+		{field: MyLatField, value: "S090 00.000", want: Valid, others: []validateTest{{field: MyLonField, value: "E123 45.678"}}},
+		{field: MyLonField, value: "E009 00.000", want: Valid, others: []validateTest{{field: MyLatField, value: "S012 34.567"}}},
+		{field: MyLonField, value: "W180 00.000", want: Valid, others: []validateTest{{field: MyLatField, value: "S012 34.567"}}},
+		{field: LatField, value: "N012 34.567", want: Valid, others: []validateTest{{field: LonField, value: "E000 00.000"}}},
+		{field: LatField, value: "S023 59.999", want: Valid, others: []validateTest{{field: LonField, value: "W000 00.000"}}},
+		{field: LonField, value: "E000 00.001", want: Valid, others: []validateTest{{field: LatField, value: "S000 00.000"}}},
+		{field: LonField, value: "W120 30.050", want: Valid, others: []validateTest{{field: LatField, value: "N000 00.000"}}},
 		{field: LatField, value: "Equator", want: InvalidError},
 		{field: LonField, value: "Greenwich", want: InvalidError},
 		{field: LatField, value: "X012 34.567", want: InvalidError},
@@ -749,9 +762,14 @@ func TestValidateLocation(t *testing.T) {
 		{field: MyLonField, value: "123 45.678E", want: InvalidError},
 		{field: MyLonField, value: `123 45' 54.321"`, want: InvalidError},
 		{field: MyLonField, value: `-123° 45' 54.321"`, want: InvalidError},
+		// Warning if one coordinate field is set but not the other
+		{field: LatField, value: "N012 34.567", want: InvalidWarning},
+		{field: LonField, value: "E012 34.567", want: InvalidWarning},
+		{field: MyLatField, value: "N012 34.567", want: InvalidWarning},
+		{field: MyLonField, value: "E012 34.567", want: InvalidWarning},
 	}
 	for _, tc := range tests {
-		testValidator(t, tc, emptyCtx, "ValidateLocation")
+		testValidator(t, tc, validateTestCtx(tc), "ValidateLocation")
 	}
 }