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Answer architecture round 3, stability round 2, product-owner round 2 and prose round 1: the CLI renders exactly the template on stdin and adds nothing, --separator defaults to empty, whitespace around JSON is dropped, a lone reference under --format allows one newline, a blank stdin is refused, an unexpected argument names the spelling to use, and the prose names one lone reference

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Lilleman auf Larv
2026-10-07 21:39:06 +02:00
committed by Lillem4n
parent 58a7b16a7f
commit e5babf413d
9 changed files with 188 additions and 182 deletions
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README.md
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@@ -12,19 +12,20 @@ echo '{/sv_SE.person}' | fejkdata # Sara Eriksson
## CLI
```sh
echo '{/sv_SE.person}' | fejkdata # Sara Eriksson
echo '{/sv_SE.person.last}' | fejkdata # Eriksson
echo '{/sv_SE.person} hihi' | fejkdata # Sara Eriksson hihi, then echo's newline
echo '{/sv_SE.address}' | fejkdata --seed 42 # the same address every run
echo '{/sv_SE.word}' | fejkdata -n 3 --separator ', ' # nät, barn, sol
fejkdata --list # every path the data offers
echo '{/misc.territory[SE].capital}' | fejkdata # Stockholm — a table's row, selected by key or name
echo '{/geo.SE.locality[Lund].street}' | fejkdata # Fjelievägen — a linked table, drawn inside the row
echo '{/sv_SE.word}' | fejkdata --data-path ./mydata # layer a directory over the shipped data
fejkdata --no-shipped-data -d ./mydata --list # only your data
echo '{"format":"name: {x}","x":["bosse","lina"]}' | fejkdata # name: bosse or name: lina
fejkdata < template.txt # a template kept in a file
fejkdata <<'EOF' # born 2003-11-27 — a quoted heredoc passes ', $ and \ as written
echo '{/sv_SE.person}' | fejkdata # Sara Eriksson
echo '{/sv_SE.person.last}' | fejkdata # Eriksson
echo '{/sv_SE.person} hihi' | fejkdata # Sara Eriksson hihi
echo '{/sv_SE.address}' | fejkdata --seed 42 # the same address every run
echo '{/sv_SE.word}' | fejkdata -n 3 # nät, barn and sol, a line each
printf '%s' '{/sv_SE.word}' | fejkdata -n 3 --separator ', ' # nät, barn, sol
fejkdata --list # every path the data offers
echo '{/misc.territory[SE].capital}' | fejkdata # Stockholm — a table's row, selected by key or name
echo '{/geo.SE.locality[Lund].street}' | fejkdata # Fjelievägen — a linked table, drawn inside the row
echo '{/sv_SE.word}' | fejkdata --data-path ./mydata # layer a directory over the shipped data
fejkdata --no-shipped-data -d ./mydata --list # only your data
echo '{"format":"name: {x}\n","x":["bosse","lina"]}' | fejkdata # name: bosse or name: lina
fejkdata < template.txt # a template kept in a file
fejkdata <<'EOF' # born 2003-11-27 — a quoted heredoc passes ', $ and \ as written
born {date(1990-01-01,2010-12-31,'2006-01-02')}
EOF
```
@@ -32,18 +33,19 @@ EOF
fejkdata renders the template on its stdin: a format string, or a JSON object, array or
string. Its `{…}` tokens reach the data by reference from the root,
`{/sv_SE.person.last}`, so shipped and `--data-path` categories are alike available,
and everything outside them prints as written; stdin that is JSON is read as JSON, so
`42`, `true` or `null` alone is refused. A reference names a category, or a field
and everything outside them prints as written. A reference names a category, or a field
inside one: each dot segment descends one level — folders, then the category (a JSON
file), then fields — and `[SE]` after a [table](#table) selects its row. `--list` prints
these paths; a template reads one as `{/path}`.
A format string keeps every byte of stdin, so `echo`'s newline renders too; `printf '%s'`
leaves it out. A JSON template or one reference alone drops one newline ending stdin,
`\n` or `\r\n`, which neither could print. One reference alone, `{/users}`, is the record
`users` under `--format`. Some shells' `echo` reads a backslash as an escape, so pipe a
What you send is what renders, and fejkdata adds nothing. A format string keeps every
byte, so `echo`, a file or a heredoc ends each render with its newline, 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
lone reference, one `{/…}` and nothing else, is the record it names under `--format`, one
newline after it allowed. Some shells' `echo` reads a backslash as an escape, so pipe a
template holding one from a quoted heredoc or a file. The rest of stdin's rules are under
[Decisions](docs/decisions.md#the-cli-renders-the-template-on-its-stdin-keeping-a-format-strings-every-byte).
[Decisions](docs/decisions.md#the-cli-renders-exactly-the-template-on-its-stdin-and-adds-nothing).
| Flag | |
|------|--|
@@ -51,7 +53,7 @@ template holding one from a quoted heredoc or a file. The rest of stdin's rules
| `--no-shipped-data` | load only the `--data-path` directories |
| `-s`, `--seed N` | same seed, version and data: identical output |
| `-n`, `--repeat N` | render the template N times (up to 1048576), each an independent draw, streamed |
| `--separator S` | between repeated values (default a newline) |
| `--separator S` | between repeated renders (default empty) |
| `--format F` | `text` (default), `json`, `ndjson`, `csv` or `sql` — a record's columns, one record per row (json frames them as an array) |
| `--table T` | the INSERT target for `--format sql` (default: a lone reference's last segment, such as `users` for `{/users}`, else `records`) |
| `--list` | print every path, then exit |
@@ -60,7 +62,8 @@ template holding one from a quoted heredoc or a file. The rest of stdin's rules
`--name value` and `--name=value` both work, a short flag's value attaches or
follows (`-n3`, `-n 3`) and short flags bundle (`-hn 3`) — see
[Decisions](docs/decisions.md#flags-follow-getopt_long); flags go anywhere, `--` ends them. Exit codes: `0` success, `1` runtime error (missing
dir, a lone reference to nothing), `2` misuse — a bad flag, an operand, nothing on stdin, or a
dir, a lone reference to nothing under `--format`), `2` misuse — a bad flag, an argument
other than a flag, an empty or unreadable stdin, nothing piped in, or a
template that does not compile. From a checkout:
`go run ./cmd/fejkdata …`.
@@ -113,8 +116,7 @@ echo '{/users}' | fejkdata --seed 1 -d ./mydata --format sql # IN
echo '{/users}' | fejkdata --seed 1 -d ./mydata --format sql --table people # INSERT into another table
```
A record is one reference alone, `{/users}`, or a template whose fields are its
columns. `--repeat` streams that many records — `json` frames them as one array document,
`--repeat` streams that many records — `json` frames them as one array document,
`ndjson` writes one object per line, `csv` a row after a header, `sql` one INSERT
per line. Only a category-level template is a record; a field, choice or folder
errors, and so does a `repeat` on
@@ -550,7 +552,7 @@ A name naming several rows is an error listing their keys, unless a row selected
before it settles which ([Linked tables](#linked-tables)). A selector is part of the path, so it works
wherever a path does: `Fake`, `FakeRecord`, a `{/misc.territory[SE].capital}` reference
and a struct tag. A dot inside the brackets belongs to the key or name, so
`city[St. Louis]` selects it. A path starts with a name, so `[SE]` alone selects nothing.
`city[St. Louis]` selects it.
### Linked tables
@@ -996,7 +998,7 @@ internal/builtinfunc/ the {name()} functions: their checks and draws, checksums,
internal/datafiles/ the walk of a data tree: its folders, its category files and the rows files beside them
internal/datatype/ the datatype a record column holds; the root's DataType is an alias of it
internal/drawstate/ the seeded randomness and the {seq()} counters a generator draws through
internal/grammar/ how the template language is written: format tokens, paths and selectors, reference sigils, identifiers, calc syntax, and whether a struct tag is a template or a path
internal/grammar/ how the template language is written: format tokens, paths and selectors, reference sigils, identifiers, calc syntax, and whether a string is a template or a path
internal/invariant/ the one phrase every package panics with when an invariant breaks
internal/proven/ what a proof knows of a value, and the bounds a calc takes from its operands
internal/rows/ a table's rows: the TSV, the options proved over it, the links between tables, row selection and draws, and the pin set one path or one named pick fixes