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Answer architecture round 4, stability round 3, product-owner round 3 and prose round 2: stdin trims JSON's own whitespace around any JSON value, the padded-JSON title names NewTemplate and the CLI, the JSON examples hold no backslash for echo, an argument's example is built only from a template or a valid reference and shell-quoted, the text scope of adding nothing, blank stdin, and the stdin decision in four paragraphs

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Lilleman auf Larv
2026-10-07 21:43:04 +02:00
committed by Lillem4n
parent e5babf413d
commit 0de54c3b15
7 changed files with 69 additions and 49 deletions
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cmd/fejkdata/main.go
+26 -19
View File
@@ -28,7 +28,7 @@ const usage = `Usage: <template> | fejkdata [flags]
fejkdata reads one template from stdin and renders it:
echo 'name: {/sv_SE.person.last}' | fejkdata
echo '{"format":"{x}\n","x":["bosse","lina"]}' | fejkdata
echo '{"format":"{x}","x":["bosse","lina"]}' | fejkdata
fejkdata < template.txt
fejkdata <<'EOF'
@@ -42,21 +42,21 @@ path into one ({/sv_SE.person.last}), a table's row by key or name
({/misc.territory[SE]}), and .. steps up from a row to the row it links to
({/geo.SE.locality..municipality.name}).
What you send is what renders, and fejkdata adds nothing: a format string keeps
In text, what you send is what renders, and fejkdata adds nothing: a format string keeps
every byte, so echo's newline ends each render, and printf '%s' sends none. -n
joins renders with --separator, empty by default. A JSON template is its JSON, the
whitespace around it dropped, so 42, true or null alone is refused. A quoted
joins renders with --separator, empty by default. A JSON template is an object, array
or string, and the whitespace around it is dropped; 42, true or null alone is refused. A quoted
heredoc, <<'EOF', passes $, a backslash or a quote as written.
With --format json, ndjson, csv or sql the template must be a record — a JSON
template whose fields are its columns, or a lone reference, {/sv_SE.person}, one
newline after it allowed — and the rows are written as one JSON array, one JSON
template whose fields are its columns, or a lone reference, one reference and nothing
else such as {/sv_SE.person}, one newline after it allowed — and the rows are written as one JSON array, one JSON
object per line, one CSV row (after a header), or one INSERT.
-d, --data-path D a data directory to layer over the shipped data (repeatable; last wins on a clash)
--format F output form: text (default), json, ndjson, csv or sql
-h, --help print this help, then exit
--list list the paths the data offers, each one a reference from the root, then exit
--list list the paths the data offers, each written after {/ in a template, then exit
--no-shipped-data load only the --data-path directories
-n, --repeat N render the template N times, 1..1048576 (default 1)
-s, --seed N same seed, version and data: identical output
@@ -279,7 +279,8 @@ func (in invocation) checkFlags() error {
const pipeHint = "echo '{/sv_SE.person}' | fejkdata"
// operandError refuses an argument that is no flag, naming the spelling that reads what
// it most likely means: stdin for -, a file for a file's name, else a template piped in.
// it most likely means: dropping it for -, a file for a file's name, else a template
// piped in.
func operandError(arg string) error {
unexpected := "unexpected argument '" + arg + "'"
if arg == "-" {
@@ -289,8 +290,10 @@ func operandError(arg string) error {
return fmt.Errorf("%s; read a file from stdin: fejkdata < %s", unexpected, shellQuoted(arg))
}
example := pipeHint
if inline, err := fejkdata.IsTemplate(arg); !inline && err == nil {
example = "echo '{/" + arg + "}' | fejkdata"
if inline, err := fejkdata.IsTemplate(arg); inline {
example = "echo " + shellQuoted(arg) + " | fejkdata"
} else if _, lone := loneReference("{/" + arg + "}"); lone && err == nil {
example = "echo " + shellQuoted("{/"+arg+"}") + " | fejkdata"
}
return fmt.Errorf("%s; the template is read from stdin: %s", unexpected, example)
}
@@ -324,9 +327,8 @@ func (in invocation) options() []fejkdata.Option {
return opts
}
// write streams the input's renders to w, repeat of them joined by the separator. A
// value that renders once renders every time, so a render failure comes before anything
// is written; a write failure surfaces from Flush, bufio keeping the first one.
// write streams the input's renders to w, repeat of them joined by the separator; a write
// failure surfaces from Flush, bufio keeping the first one.
func (in invocation) write(f *fejkdata.Generator, src input, w io.Writer) error {
if in.writesRecords() {
return in.writeRecords(f, src, w)
@@ -421,11 +423,15 @@ func defaultTable(path string) string {
// inputError marks a failure that is the input's own fault — no template, one that does
// not compile, or a stdin that cannot be read. run reports it as misuse (exit 2, with a
// pointer to --help), unlike a lone reference to nothing, which is a runtime error (exit 1).
// pointer to --help), unlike a lone reference to nothing under --format, which is a runtime
// error (exit 1).
type inputError struct{ error }
func (e inputError) Unwrap() error { return e.error }
// jsonSpace is the whitespace JSON allows around a value.
const jsonSpace = " \t\r\n"
// input is what stdin holds: the template, and the path a lone reference names as a
// record.
type input struct {
@@ -433,15 +439,16 @@ type input struct {
record string
}
// parseInput reads stdin. A format string is its every byte; a JSON template sheds the
// whitespace around it; a lone reference names a record less one newline ending it.
// parseInput reads stdin. A format string is every byte of stdin; a JSON template drops
// the whitespace around it; a lone reference names a record, with one newline ending it
// allowed.
func parseInput(raw string) (input, error) {
trimmed := strings.TrimSpace(raw)
trimmed := strings.Trim(raw, jsonSpace)
if trimmed == "" {
return input{}, fmt.Errorf("stdin holds no template: %s", pipeHint)
}
template := raw
if strings.ContainsRune(`{["`, rune(trimmed[0])) && json.Valid([]byte(trimmed)) {
if json.Valid([]byte(trimmed)) {
template = trimmed
}
text, found := strings.CutSuffix(template, "\n")
@@ -485,7 +492,7 @@ func spacedReference(template string, err error) error {
// shellQuoted is s as a shell reads it back: bare where it holds nothing a shell expands.
func shellQuoted(s string) string {
if s != "" && !strings.ContainsAny(s, " \t'\"$`\\*?[]{}()<>|&;#~!") {
if s != "" && !strings.ContainsAny(s, " \t\r\n'\"$`\\*?[]{}()<>|&;#~!") {
return s
}
return "'" + strings.ReplaceAll(s, "'", `'\''`) + "'"
cmd/fejkdata/main_test.go
+4 -1
View File
@@ -250,7 +250,8 @@ func TestRunTakesNoOperand(t *testing.T) {
}{
{[]string{"sv_SE.person"}, "echo '{/sv_SE.person}' | fejkdata"},
{[]string{"{/sv_SE.person}"}, "echo '{/sv_SE.person}' | fejkdata"},
{[]string{"name: {/sv_SE.person.last}"}, "echo '{/sv_SE.person}' | fejkdata"},
{[]string{"name: {/sv_SE.person.last}"}, "echo 'name: {/sv_SE.person.last}' | fejkdata"},
{[]string{"geo.US.locality[O'Fallon].name"}, `echo '{/geo.US.locality[O'\''Fallon].name}' | fejkdata`},
{[]string{"en_US.address"}, "echo '{/en_US.address}' | fejkdata"},
{[]string{"-"}, "drop it"},
{[]string{file}, "fejkdata < " + file},
@@ -480,6 +481,8 @@ func TestRunTemplateMisuse(t *testing.T) {
"name: {/no.such.path}": "no entry",
"a } b": "}}",
"42": "number",
"42\n": "number",
"true\n": "boolean",
"{//sv_SE.person}": "write {/sv_SE.person}",
} {
code, out, errb := runOut(stdin, "--seed", "1")