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v/vlib/toml/README.md

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## Description
`toml` is a fully fledged [TOML v1.0.0](https://toml.io/en/v1.0.0) compatible parser written in pure V.
The module is tested against the [official compliance tests](https://github.com/toml-lang/compliance).
## Usage
Parsing files or `string`s containing TOML is easy.
Simply import the `toml` module and do:
```v ignore
doc1 := toml.parse_text(<string content>) or { panic(err) }
doc2 := toml.parse_file(<file path>) or { panic(err) }
```
## Example
Here we parse the official [TOML example](https://github.com/toml-lang/toml/blob/3b11f6921da7b6f5db37af039aa021fee450c091/README.md#Example)
and print out some values.
```v
import toml
const toml_text = '# This is a TOML document.
title = "TOML Example"
[owner]
name = "Tom Preston-Werner"
dob = 1979-05-27T07:32:00-08:00 # First class dates
[database]
server = "192.168.1.1"
ports = [ 8000, 8001, 8002 ]
connection_max = 5000
enabled = true
[servers]
# Indentation (tabs and/or spaces) is allowed but not required
[servers.alpha]
ip = "10.0.0.1"
dc = "eqdc10"
[servers.beta]
ip = "10.0.0.2"
dc = "eqdc10"
[clients]
data = [ ["gamma", "delta"], [1, 2] ]
# Line breaks are OK when inside arrays
hosts = [
"alpha",
"omega"
]'
fn main() {
doc := toml.parse_text(toml_text) or { panic(err) }
title := doc.value('title').string()
println('title: "${title}"')
ip := doc.value('servers.alpha.ip').string()
println('Server IP: "${ip}"')
}
```
## Value retrieval
The `toml` module supports easy retrieval of values from
TOML documents by using a small and simple query syntax
as argument to the `value()` function.
Keys in map entries are denoted by `.` and array entries
uses `[<int>]`. Quoted keys are also supported by using
the delimiters `"` or `'`.
`doc.value('table.array[0].a."b.c"')`
To query for a value that might not be in the document you
can use the `.default_to(...)` function to provide a
default value.
For cases where a default value might not be appropiate or
to check if a value exists you can use `doc.value_opt('query')?`
instead.
```v
import toml
const toml_text = '
val = true
[table]
array = [
{ a = "A" },
{ b = "B" }
]
'
doc := toml.parse_text(toml_text) or { panic(err) }
assert doc.value('val').bool() == true
assert doc.value('table.array[0].a').string() == 'A'
// Provides a default value
assert doc.value('non.existing').default_to(false).bool() == false
// Check if value exist
// doc.value_opt('should.exist') or { ... }
// or
if value := doc.value_opt('table.array[1].b') {
assert value.string() == 'B'
}
// You can pass parts of the TOML document around
// and still use .value()/.value_opt() to get the values
arr := doc.value('table.array')
assert arr.value('[1].b').string() == 'B'
```
### Conversion
Any TOML value can be converted to a V equivalent type.
TOML values are represented as the `toml.Any` sum-type that
can be converted to a V type.
| TOML value | V conversion (via `toml.Any`) |
| -------------------------- | ----------------------------- |
| val = "Basic string" | .string() |
| val = 'Literal string' | .string() |
| val = true | .bool() |
| val = 1979-05-27T07:32:00Z | .datetime() (toml.DateTime) |
| val = 1979-05-27 | .date() (toml.Date) |
| val = 07:32:59 | .time() (toml.Time) |
| val = 3.14 | .f32() / .f64() |
| val = 100 | .int() / .i64() / .u64() |
Read more about values in the [TOML specification](https://toml.io/en/v1.0.0#spec).
## TOML to JSON
The `toml.to` module supports easy serialization of any TOML to JSON.
```v
import toml
import toml.to
const toml_text = '
val = true
[table]
array = [
{ a = "A" },
{ b = "B" }
]
'
doc := toml.parse_text(toml_text) or { panic(err) }
assert to.json(doc) == '{ "val": true, "table": { "array": [ { "a": "A" }, { "b": "B" } ] } }'
```