Handle single combination in limits

src/combination/name.js

@@ -3,6 +3,12 @@ import { titleColor, noteColor } from '../report/utils/colors.js'
 import { omitCombNoDimensions } from './filter.js'
 import { getCombinationIds } from './ids.js'
 
+// Retrieve error message prefix showing a combination's dimension ids
+export const getCombinationPrefix = function (combination, noDimensions) {
+  const combinationName = getCombinationName(combination, noDimensions)
+  return combinationName === '' ? '' : `In ${combinationName}:\n`
+}
+
 // Retrieve string with each combination's dimension id.
 // This is in contrast with `combinationTitle`:
 //  - `combinationTitle*` uses dimensions titles, which is more useful at

src/history/compare/limit.js

@@ -1,4 +1,4 @@
-import { getCombinationName } from '../../combination/name.js'
+import { getCombinationPrefix } from '../../combination/name.js'
 import { UserError } from '../../error/main.js'
 import { matchSelectors } from '../../select/match.js'
 
@@ -74,12 +74,11 @@ const isBelowThreshold = function (diff, threshold, higher) {
 // `getCombinationName` passes an empty `noDimensions` since `dimensions` are
 // already filtered out `programmaticResult`.
 const getLimitError = function ({ diff, threshold, higher, combination }) {
-  const combinationName = getCombinationName(combination, [])
+  const combinationPrefix = getCombinationPrefix(combination, [])
   const thresholdStr = threshold * PERCENTAGE_RATIO
   const diffStr = serializeDiff(diff)
   const higherStr = higher ? 'higher' : 'lower'
-  return `In ${combinationName}:
-The combination should be at most ${thresholdStr}% ${higherStr} but it is ${diffStr}% ${higherStr}.`
+  return `${combinationPrefix}The combination should be at most ${thresholdStr}% ${higherStr} but it is ${diffStr}% ${higherStr}.`
 }
 
 const serializeDiff = function (diff) {