builtins.go

@@ -472,17 +472,28 @@ func iban(r rng, cc string) string {
 
 const dayLayout = "2006-01-02"
 
-// Alike in no field; layoutDay differs from layoutProbe in its date fields only.
+// Alike in no field; layoutDay differs from layoutProbe in its date fields only,
+// layoutClock in its clock fields only.
 var (
 	layoutProbe  = time.Date(2001, 2, 3, 4, 5, 6, 0, time.UTC)
 	layoutProbe2 = time.Date(2010, 11, 12, 13, 14, 15, 0, time.UTC)
 	layoutDay    = time.Date(2010, 11, 12, 4, 5, 6, 0, time.UTC)
+	layoutClock  = time.Date(2001, 2, 3, 13, 14, 15, 0, time.UTC)
 )
 
+// quotedLayout reports whether an arg carries the single quotes a layout is written in.
+func quotedLayout(a string) bool {
+	return len(a) >= 2 && a[0] == '\'' && a[len(a)-1] == '\''
+}
+
 // layoutArg is the Go layout a quoted arg holds, refused when unquoted or constant.
 func layoutArg(a string) (string, error) {
-	if len(a) < 2 || a[0] != '\'' || a[len(a)-1] != '\'' {
+	if !quotedLayout(a) {
-		return "", fmt.Errorf("layout %s is not quoted; write '%s'", a, strings.Trim(a, "'"))
+		bare := strings.Trim(a, `'"`)
+		if strings.HasPrefix(a, `"`) || strings.HasSuffix(a, `"`) {
+			return "", fmt.Errorf("layout %s is double-quoted; write '%s'", a, bare)
+		}
+		return "", fmt.Errorf("layout %s is not quoted; write '%s', which a shell keeps only inside a double-quoted argument", a, bare)
 	}
 	layout := a[1 : len(a)-1]
 	if layoutProbe.Format(layout) == layoutProbe2.Format(layout) {
@@ -501,18 +512,31 @@ func layoutOf(a string) string {
 }
 
 // layoutArity checks a call ending in a layout takes n args, naming the quoted
-// layout when an unquoted one split into more.
+// layout where an unquoted one split into more.
 func layoutArity(name string, n int, a []string) error {
 	if len(a) == n {
 		return nil
 	}
 	hint := ""
-	if len(a) > n {
+	if len(a) > n && !split(a[n-1:]) {
 		hint = fmt.Sprintf("; a layout holding a comma is quoted: '%s'", strings.Join(a[n-1:], ", "))
 	}
-	return fmt.Errorf("%s takes %d args, got %d%s", name, n, len(a), hint)
+	return fmt.Errorf("%s takes %d argument%s, got %d%s", name, n, plural(n), len(a), hint)
 }
 
+// split reports whether the surplus args already hold a quoted layout, which no
+// comma split apart.
+func split(a []string) bool {
+	for _, arg := range a {
+		if quotedLayout(arg) {
+			return true
+		}
+	}
+	return false
+}
+
+func plural(n int) string { return map[bool]string{true: "s"}[n != 1] }
+
 func dateArgs(_ map[string]node, a []string) error {
 	if err := layoutArity("date", 3, a); err != nil {
 		return err
@@ -525,8 +549,8 @@ func dateArgs(_ map[string]node, a []string) error {
 	if err != nil {
 		return fmt.Errorf("date(from,to,layout): to %q is not a YYYY-MM-DD date", a[1])
 	}
-	if !from.Before(to) {
+	if to.Before(from) {
-		return fmt.Errorf("date(from,to,layout): from %s is not before to %s", a[0], a[1])
+		return fmt.Errorf("date(from,to,layout): from %s is after to %s", a[0], a[1])
 	}
 	layout, err := layoutArg(a[2])
 	if err != nil {
@@ -535,6 +559,9 @@ func dateArgs(_ map[string]node, a []string) error {
 	if layoutProbe.Format(layout) == layoutDay.Format(layout) {
 		return fmt.Errorf("date(from,to,layout): '%s' names no date field; write time('%s')", layout, layout)
 	}
+	if from.Equal(to) && layoutProbe.Format(layout) == layoutClock.Format(layout) {
+		return fmt.Errorf("date(%s,%s,'%s') is the constant %q; write it as text", a[0], a[1], layout, from.Format(layout))
+	}
 	return nil
 }
 

record.go

@@ -140,6 +140,10 @@ func (f *Generator) FakeRecord(path string) (*Record, error) {
 		return nil, fmt.Errorf("fejkdata: %s descends into %q, a field; only a category-level template is a record", path, tail[0])
 	}
 	shape := f.recordShapeOf(n)
+	if errors.Is(shape.err, errNoColumns) {
+		column := path[strings.LastIndex(path, ".")+1:]
+		return nil, fmt.Errorf("fejkdata: %s %w; render it as a column of one: '{\"format\":\"\",\"%s\":\"{/%s}\"}'", path, shape.err, column, path)
+	}
 	if shape.err != nil {
 		return nil, fmt.Errorf("fejkdata: %s %w", path, shape.err)
 	}
@@ -227,6 +231,10 @@ func (f *Generator) FakeRecordTemplate(input string) (*Record, error) {
 	return t.Fake(), nil
 }
 
+// errNoColumns is the one record fence a path can answer, so its entry point names
+// the record to write instead.
+var errNoColumns = errors.New("has no fields, so no columns")
+
 // recordOf is the fence both record entry points pass. The columns come back with
 // the template, fixed for every draw the caller goes on to make.
 func recordOf(n node) (*template, []Column, error) {
@@ -239,7 +247,7 @@ func recordOf(n node) (*template, []Column, error) {
 	}
 	names := recordColumns(t)
 	if len(names) == 0 {
-		return nil, nil, errors.New("has no fields, so no columns")
+		return nil, nil, errNoColumns
 	}
 	if !t.record {
 		return nil, nil, fmt.Errorf("carries repeat %d, which composes its format into one string; a record projects columns instead — drop the repeat and render the record again for more rows", t.repeat)

table.go

@@ -14,6 +14,7 @@ import (
 // cell of the row a render pinned; a cell carrying tokens compiles to a string node.
 type table struct {
 	category string
+	path     string // the category's path from the data root, set when the tables are linked
 	file     string
 	format   *template // fields are the column nodes
 	columns  []string
@@ -350,6 +351,7 @@ func linkTables(root map[string]node) error {
 					return err
 				}
 			case *table:
+				n.path = path
 				if n.parent < 0 {
 					continue
 				}
@@ -508,7 +510,7 @@ func (t *table) under(r int, a *table, pr int) bool {
 // naming several rows resolves inside the ancestors pinned in d.
 func (t *table) find(sel string, d *draws) (int, error) {
 	if t.key < 0 && t.name < 0 {
-		return 0, fmt.Errorf("%s has no key or name column to select a row by", t.category)
+		return 0, fmt.Errorf("%s has no key or name column to select a row by", t.spelledPath())
 	}
 	if r, ok := t.byKey[sel]; ok {
 		return r, nil
@@ -521,7 +523,7 @@ func (t *table) find(sel string, d *draws) (int, error) {
 	case 1:
 		return rows[0], nil
 	case 0:
-		return 0, fmt.Errorf("no row of %s has key or name %q", t.category, sel)
+		return 0, fmt.Errorf("no row of %s has key or name %q", t.spelledPath(), sel)
 	}
 	keys := make([]string, len(rows))
 	for i, r := range rows {
@@ -531,14 +533,24 @@ func (t *table) find(sel string, d *draws) (int, error) {
 			keys[i] = t.cell(r, t.key)
 		}
 	}
+	listed := strings.Join(keys, ", ")
 	if t.key < 0 {
-		return 0, fmt.Errorf("%q names %d rows of %s; select it inside its %s, one of %v", sel, len(rows), t.category, t.parentT.category, keys)
+		return 0, fmt.Errorf("%q names %d rows of %s; select it inside its %s, one of %s", sel, len(rows), t.spelledPath(), t.parentT.spelledPath(), listed)
 	}
 	inside := ""
 	if t.parentT != nil {
 		inside = fmt.Sprintf(", or select it inside its %s", t.parentT.category)
 	}
-	return 0, fmt.Errorf("%q names %d rows of %s; select one by key, one of %v%s", sel, len(rows), t.category, keys, inside)
+	return 0, fmt.Errorf("%q names %d rows of %s; select one by key, one of %s%s", sel, len(rows), t.spelledPath(), listed, inside)
+}
+
+// spelledPath is the path a selector on t is written at, the category's own name
+// until the tables are linked.
+func (t *table) spelledPath() string {
+	if t.path == "" {
+		return t.category
+	}
+	return t.path
 }
 
 // selectorSpelling is how a path writes a selected row, for messages: by key, or
@@ -546,7 +558,7 @@ func (t *table) find(sel string, d *draws) (int, error) {
 func (t *table) selectorSpelling(r int) string {
 	switch {
 	case t.key >= 0:
-		return t.category + "[" + t.cell(r, t.key) + "]"
+		return t.spelledPath() + "[" + t.cell(r, t.key) + "]"
 	case t.name >= 0:
 		return t.parentT.selectorSpelling(t.parentRow(r)) + "." + t.category + "[" + t.cell(r, t.name) + "]"
 	}

template.go

@@ -125,7 +125,7 @@ func checkFunc(body string, fields map[string]node) error {
 		return fmt.Errorf("token {%s}: unknown function %q", body, name)
 	}
 	if b.arity >= 0 && len(args) != b.arity {
-		return fmt.Errorf("token {%s}: %s takes %d args, got %d", body, name, b.arity, len(args))
+		return fmt.Errorf("token {%s}: %s takes %d argument%s, got %d", body, name, b.arity, plural(b.arity), len(args))
 	}
 	if b.check != nil {
 		if err := b.check(fields, args); err != nil {