longer error messages

cli/lib/validation.ts

@@ -2,6 +2,8 @@ import type { Literal, NamedNode, Quad } from '@rdfjs/types'
 import { turtle } from '@tpluscode/rdf-string'
 import type { Context } from 'barnard59-core/lib/Pipeline'
 import { validateQuad } from 'rdf-validate-datatype'
+import TermMap from '@rdfjs/term-map'
+import { xsd } from '@tpluscode/rdf-ns-builders'
 
 export function validate(this: Context, quad: Quad): Quad {
   if (!validateQuad(quad)) {
@@ -18,11 +20,44 @@ function quadToString(quad: Quad): string {
   })
 }
 
+// consider replacing should with may
+const messages = new TermMap<NamedNode, string>([
+  [xsd.boolean, 'Boolean values should be formatted as "true" and "false" (or "0" and "1"). See also https://www.w3.org/TR/xmlschema-2/#boolean.'],
+  [xsd.date, 'Dates should be formatted as YYYY-MM-DD as specified by ISO 8601. See also https://www.w3.org/TR/xmlschema-2/#date.'],
+  [xsd.dateTime, 'Values should be formatted as YYYY-MM-DDThh:mm:ss. See also https://www.w3.org/TR/xmlschema-2/#dateTime.'],
+  [xsd.gDay, 'Days should be formatted as DD. See also https://www.w3.org/TR/xmlschema-2/#gDay.'],
+  [xsd.decimal, 'Decimals should be formatted as digits, possibly with a period to separate the fractional part. An optional leading sign is allowed. with See also https://www.w3.org/TR/xmlschema-2/#decimal.'],
+  [xsd.integer, 'Integers should be formatted as digits, with an optional leading sign. See also https://www.w3.org/TR/xmlschema-2/#integer.'],
+  [xsd.gMonth, 'Months should be formatted as MM. See also https://www.w3.org/TR/xmlschema-2/#gMonth.'],
+  [xsd.string, 'See also https://www.w3.org/TR/xmlschema-2/#string.'],
+  [xsd.time, 'Values should be formatted as hh:mm:ss. See also https://www.w3.org/TR/xmlschema-2/#time.'],
+  [xsd.gYear, 'Years should be formatted as YYYY. See also https://www.w3.org/TR/xmlschema-2/#gYear.'],
+  [xsd.gYearMonth, 'Values should be formatted as YYYY-MM. See also https://www.w3.org/TR/xmlschema-2/#gYearMonth.'],
+])
+
+const typeName = new TermMap<NamedNode, string>([
+  [xsd.boolean, 'boolean'],
+  [xsd.date, 'date'],
+  [xsd.dateTime, 'dateTime'],
+  [xsd.gDay, 'day'],
+  [xsd.decimal, 'decimal'],
+  [xsd.integer, 'integer'],
+  [xsd.gMonth, 'month'],
+  [xsd.string, 'string'],
+  [xsd.time, 'time'],
+  [xsd.gYear, 'year'],
+  [xsd.gYearMonth, 'year+month'],
+])
+
 function errorMessage(quad: Quad): string {
   const literal = quad.object as Literal
   if (!literal.datatype) {
     return `Invalid datatype for non-literal ${literal.value}`
   }
+  const message = messages.get(literal.datatype)
+  if (message) {
+    return `the value "${literal.value}" in your CSV file does not conform to the selected datatype "${typeName.get(literal.datatype)}".\n${message}`
+  }
 
   return `literal "${literal.value}" is not a valid value for datatype <${literal.datatype.value}>.`
 }