Add support for @file (#7)

- Use `%-s`, `%-q`, `%*-s`, `%*-q`, `%**-s`, `%**-q` syntax to read from stdin.
- Use `%(NAME@FILE)` syntax to read default value from file.
- Use `%(NAME@-)` syntax to read default value from stdin.
- Use `NAME@FILE` to pass default value for named placeholder from file.
- Use `NAME@-` to pass default value for named placeholder from stdin.
- Stdin values are separated by null (`\0`).

Also, display better error for invalid expandable placeholder syntax.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "jf"
-version = "0.3.3"
+version = "0.4.0"
 edition = "2021"
 authors = ["Arijit Basu <hi@arijitbasu.in>"]
 description = 'A small utility to safely format and print JSON objects in the commandline'

README.md

@@ -36,7 +36,7 @@ nix-env -f https://github.com/NixOS/nixpkgs/tarball/nixos-unstable -iA jf
 ### USAGE
 
 ```bash
-jf TEMPLATE [VALUE]... [NAME=VALUE]...
+jf TEMPLATE [VALUE]... [NAME=VALUE]... [NAME@FILE]...
 ```
 
 Where TEMPLATE may contain the following placeholders:
@@ -46,26 +46,33 @@ Where TEMPLATE may contain the following placeholders:
 - `%v` the `jf` version number
 - `%%` a literal `%` character
 
-And [VALUE]... [NAME=VALUE]... are the values for the placeholders.
+And [VALUE]... [NAME=VALUE]... [NAME@FILE]... are the values for the placeholders.
 
 ### SYNTAX
 
-- `%s` `%q` posiitonal placeholder
-- `%(NAME)s` `%(NAME)q` named placeholder
+- `%s` `%q` read positional argument
+- `%-s` `%-q` read stdin
+- `%(NAME)s` `%(NAME)q` read named value from argument
 - `%(NAME=DEFAULT)s` `%(NAME=DEFAULT)q` placeholder with default value
-- `%(NAME?)s` `%(NAME?)q` nullable placeholder that defaults to `null`
+- `%(NAME@FILE)s` `%(NAME@FILE)q` read default value from file path
+- `%(NAME@-)s` `%(NAME@-)q` read default value from stdin
+- `%(NAME?)s` `%(NAME?)q` nullable placeholder that defaults to null
 - `%(NAME)?s` `%(NAME)?q` optional placeholder that defaults to blank
-- `%*s` `%*q` expand positional values as array items
-- `%**s` `%**q` expand positional values as key value pairs
-- `%(NAME)*s` `%(NAME)*q` expand named values as array items
-- `%(NAME)**s` `%(NAME)**q` expand named values as key value pairs
+- `%*s` `%*q` expand positional args as array items
+- `%*-s` `%*-q` expand stdin as array items
+- `%**s` `%**q` expand positional args as key value pairs
+- `%**-s` `%**-q` expand stdin as key value pairs
+- `%(NAME)*s` `%(NAME)*q` expand named args as array items
+- `%(NAME)**s` `%(NAME)**q` expand named args as key value pairs
 
 ### RULES
 
 - Pass values for positional placeholders in the same order as in the template.
+- Pass values to stdin following the order and separate them with null byte (`\0`).
 - Pass values for named placeholders using `NAME=VALUE` syntax.
 - Pass values for named array items using `NAME=ITEM_N` syntax.
 - Pass values for named key value pairs using `NAME=KEY_N NAME=VALUE_N` syntax.
+- Use `NAME@FILE` syntax to read from file where FILE can be `-` for stdin.
 - Do not declare or pass positional placeholders or values after named ones.
 - Expandable positional placeholder should be the last placeholder in a template.
 
@@ -78,16 +85,15 @@ jf %s 1
 jf %q 1
 # "1"
 
-jf [%*s] 1 2 3
-# [1,2,3]
-
-jf {%**q} one 1 two 2 three 3
+jf '{%**q}' one 1 two 2 three 3
 # {"one":"1","two":"2","three":"3"}
 
+seq 1 3 | xargs printf '%s\0' | jf '[%*-s]'
+# [1,2,3]
+
 jf "{%q: %(value=default)q, %(bar)**q}" foo value=bar bar=biz bar=baz
 # {"foo":"bar","biz":"baz"}
 
-
 jf "{str or bool: %(str)?q %(bool)?s, nullable: %(nullable?)q}" str=true
 # {"str or bool":"true","nullable":null}
 

assets/jf.1

@@ -2,7 +2,7 @@
 .TH jf  "1" "" ""
 .SH USAGE
 
-jf TEMPLATE [VALUE]\.\.\. [NAME=VALUE]\.\.\.
+jf TEMPLATE [VALUE]\.\.\. [NAME=VALUE]\.\.\. [NAME@FILE]\.\.\.
 .PP
 Where TEMPLATE may contain the following placeholders:
 .TP
@@ -22,56 +22,80 @@ the `jf` version number
 `%%`
 a literal `%` character
 .PP
-And [VALUE]\.\.\. [NAME=VALUE]\.\.\. are the values for the placeholders.
+And [VALUE]\.\.\. [NAME=VALUE]\.\.\. [NAME@FILE]\.\.\. are the values for the placeholders.
 .SH SYNTAX
 
 .TP
 .B
 `%s`
-`%q`                posiitonal placeholder
+`%q`                read positional argument
+.TP
+.B
+`%\fB-s\fP`
+`%\fB-q\fP`               read stdin
 .TP
 .B
 `%(NAME)s`
-`%(NAME)q`          named placeholder
+`%(NAME)q`          read named value from argument
 .TP
 .B
 `%(NAME=DEFAULT)s`
 `%(NAME=DEFAULT)q`  placeholder with default value
 .TP
 .B
+`%(NAME@FILE)s`
+`%(NAME@FILE)q`     read default value from file path
+.TP
+.B
+`%(NAME@-)s`
+`%(NAME@-)q`        read default value from stdin
+.TP
+.B
 `%(NAME?)s`
-`%(NAME?)q`         nullable placeholder that defaults to `null`
+`%(NAME?)q`         nullable placeholder that defaults to null
 .TP
 .B
 `%(NAME)?s`
 `%(NAME)?q`         optional placeholder that defaults to blank
 .TP
 .B
 `%*s`
-`%*q`               expand positional values as array items
+`%*q`               expand positional args as array items
+.TP
+.B
+`%*\fB-s\fP`
+`%*\fB-q\fP`              expand stdin as array items
 .TP
 .B
 `%**s`
-`%**q`              expand positional values as key value pairs
+`%**q`              expand positional args as key value pairs
+.TP
+.B
+`%**\fB-s\fP`
+`%**\fB-q\fP`             expand stdin as key value pairs
 .TP
 .B
 `%(NAME)*s`
-`%(NAME)*q`         expand named values as array items
+`%(NAME)*q`         expand named args as array items
 .TP
 .B
 `%(NAME)**s`
-`%(NAME)**q`        expand named values as key value pairs
+`%(NAME)**q`        expand named args as key value pairs
 .SH RULES
 
 .IP \(bu 3
 Pass values for positional placeholders in the same order as in the template.
 .IP \(bu 3
+Pass values to stdin following the order and separate them with null byte (`\0`).
+.IP \(bu 3
 Pass values for named placeholders using `NAME=VALUE` syntax.
 .IP \(bu 3
 Pass values for named array items using `NAME=ITEM_N` syntax.
 .IP \(bu 3
 Pass values for named key value pairs using `NAME=KEY_N NAME=VALUE_N` syntax.
 .IP \(bu 3
+Use `NAME@FILE` syntax to read from file where FILE can be `-` for stdin.
+.IP \(bu 3
 Do not declare or pass positional placeholders or values after named ones.
 .IP \(bu 3
 Expandable positional placeholder should be the last placeholder in a template.
@@ -86,13 +110,13 @@ Run: jf %q 1
 .IP \(bu 3
 Out: "1"
 .IP \(bu 3
-Run: jf [%*s] 1 2 3
+Run: jf '{%**q}' one 1 two 2 three 3
 .IP \(bu 3
-Out: [1,2,3]
+Out: {"one":"1","two":"2","three":"3"}
 .IP \(bu 3
-Run: jf {%**q} one 1 two 2 three 3
+Run: seq 1 3 | xargs printf '%s\0' | jf '[%*\fB-s\fP]'
 .IP \(bu 3
-Out: {"one":"1","two":"2","three":"3"}
+Out: [1,2,3]
 .IP \(bu 3
 Run: jf "{%q: %(value=default)q, %(bar)**q}" foo value=bar bar=biz bar=baz
 .IP \(bu 3