configs: Return diagnostics (almost) directly from ParseProviderSourceString

This function can already produce suitable diagnostic messages which we'd
like to preserve, but it cannot produce source location information, and
so we'll amend the diagnostics to include that on the way out while
retaining all of the other values in the diagnostics.

configs/module.go

@@ -183,18 +183,17 @@ func (m *Module) appendFile(file *File) hcl.Diagnostics {
 		if reqd.Source.SourceStr != "" {
 			var sourceDiags tfdiags.Diagnostics
 			fqn, sourceDiags = addrs.ParseProviderSourceString(reqd.Source.SourceStr)
-			if sourceDiags.HasErrors() {
-				for i := range sourceDiags {
-					if sourceDiags[i].Severity() == tfdiags.Error {
-						diags = append(diags, &hcl.Diagnostic{
-							Severity: hcl.DiagError,
-							Summary:  "Invalid provider source string",
-							Detail:   sourceDiags[i].Description().Detail,
-							Subject:  &reqd.Source.DeclRange,
-						})
-					}
+			hclDiags := sourceDiags.ToHCL()
+			// The diagnostics from ParseProviderSourceString don't contain
+			// source location information because it has no context to compute
+			// them from, and so we'll add those in quickly here before we
+			// return.
+			for _, diag := range hclDiags {
+				if diag.Subject == nil {
+					diag.Subject = reqd.Source.DeclRange.Ptr()
 				}
 			}
+			diags = append(diags, hclDiags...)
 		} else {
 			fqn = addrs.NewLegacyProvider(reqd.Name)
 		}