D 2018-07-04T18:51:33.930
L config
N text/x-markdown
P 3c3385ebf38e6c24a7070a7afa803aba36b6c2f6873b87c98f2f9d02aaa551f7
U mario
W 5011
## # config: {…}
The `config:` field lists feature- or application-level settings. It's often multiline:
# config:
# { name: linky, type: bool, description: autolink urls }
# { name: xy.title, type: str, value: "blog title" }
# { name: perm, type: select, select: 3=USER|2=EX|1=SUP|0=KERN }
[PMD](wiki/Plugin+Meta+Data) is about uniform feature lookup and configurability. To keep it brief but support enough variation, each entry is a <acronym title="JSON, but quotes optional">JSOL</acronym>-dictionary.
#### {
<table class="cnt-tbl">
<tr>
<th><code>name:</code></th>
<td>associates some variable/constant/expression to a setting.</td>
</tr>
<tr>
<th><code>type:</code></th>
<td> A few common types may cover 90% of configuration needs.
<table>
<tr>
<th><code>bool</code></th>
<td>would render as checkbox often.</td>
</tr>
<tr>
<th><code>str</code></th>
<td>for plain textual content.</td>
</tr>
<tr>
<th><code>int</code></th>
<td>verifies the value to be numeric.</td>
</tr>
<tr>
<th><code>select</code></th>
<td> defining a predefined list of defaults.</td>
</tr>
</table>
</td>
</tr>
<tr>
<th><code>select:</code></tt>
<td>With <code>select: "aaa┃bbb┃ccc"</code> being the alternatives attribute for
combobox options.</td>
</tr>
<tr>
<th><code>description:</code></th>
<td>holds some elaboration on the key name.</td>
</tr>
<tr>
<th><code>value:</code></th>
<td>just sets a default</td>
</tr>
</table>
#### }
## `select:` alternatives
The syntax for `select:` is
* preferrably `"alt|alt|alt"`
* or with optional title `"1=title|2=alternative|3=…"`.
* Though implementations may allow to use `,` comma, `;` semicolon or `|` dash as separator.
* Or allow both `:` and `=` to separate keys+values. (Too much flexibility makes it ambigious however.)
## Custom types
Apart from providing aliases for the base types, a plugin API might provide its own custom set of setting types:
| type | alias | usage |
------------------------
| `int` | `integer` / `numeric` | numbers |
| `bool` | `boolean` / `checkbox` | true/false |
| `str` | `string` / `numeric` | string |
| `select` | `multi` / `dropdown` | see select: alternatives |
| `text` | `textarea` / `long` | longer `string` type (= renders as textarea) |
| `color` | `rgb` | graphical color picker |
| `file` | `filechooser` | setting should be a valid filename |
| `table`| `csv` / `list` | for supporting more complex (Excel-style) setting lists. |
| `dict` | `hashtable` | complex dictionary (Excel-style) setting field. |
Again, supporting base type aliases (str=string) is very advisable. But complex types (table/dict) often cause too much effort for basic plugin/config systems. There's no need to cram in support for rarely used features.
## Other fields
Other per-config `{…}` attributes migh encompass
| `category:` | grouping config options (else inherited from plugin) |
| `class:` | either decoration or additional type qualifier |
| `arg:` | declares a commandline argument instead of global app setting |
| `param:` | plugin invocation argument instead of global app flag |
There's some paritiy with the main plugin meta fields. Except that config entries should not have a nested config: attribute, of course^^
## Storage and key `name:`
Notably this scheme just defines a list of available options. It does **not**
prescribe if they're stored in an `.ini`, `.json`, `xml` or code file, or a database
perhaps.
Applications might utilize different stores even, and dispatch depending on
the `name:` syntax
* For example `name: ALL_UPPERCASE` might become a code constant,
* While `name: sectioned.feature.option` indicated an INI setting,
* Or `name: "$cfg.plugins[after][]"` even a literal code target.
So names can be somewhat free-form. I'd avoid including the `$` sigil
however, or spaces obviously. Mostly-alphunumeric and dotted keys are
certainly most versatile.
## Regex tokenizer
You can get by with a somewhat simple regex extractor for this config
scheme. It's simply finding `{…}` pairs, then splitting key-value pairs,
and handling optional quoting.
* Which allows syntax alternatives `[:=>]+` for key-value pairs.
* Same as shortened/aliased type names add some user-friendliness.
Of course a stringent JSON-parser could be used. But that's obstructing
maintanability, and buys little performance-wise. (Plugin or option
management is rarely done during runtime; but confined to some admin
or installer UI.)
## Purpose
Once config options are easily parseable, it quickly pays off to implement
a centralized option/admin UI. And it sometimes can be combined with plugin
configuration itself. Which is why plugin meta data defines this simple
scheme.
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