66 lines
2.8 KiB
Markdown
66 lines
2.8 KiB
Markdown
Tags format
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=============
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When creating the `json` file describing your layer or theme, you'll have to add a few tags to describe what you want. This document gives an overview of what every expression means and how it behaves in edge cases.
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Strict equality
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---------------
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Strict equality is denoted by `key=value`. This key matches __only if__ the keypair is present exactly as stated.
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**Only normal tags (eventually in an `and`) can be used in places where they are uploaded**. Normal tags are used in the `mappings` of a [TagRendering] (unless `hideInAnswer` is specified), they are used in `addExtraTags` of [Freeform] and are used in the `tags`-list of a preset.
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If a different kind of tag specification is given, your theme will fail to parse.
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### If key is not present
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If you want to check if a key is not present, use `key=` (pronounce as *key is empty*). A tag collection will match this if `key` is missing or if `key` is a literal empty value.
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### Removing a key
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If a key should be deleted in the OpenStreetMap-database, specify `key=` as well. This can be used e.g. to remove a fixme or value from another mapping if another field is filled out.
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Strict not equals
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-----------------
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To check if a key does _not_ equal a certain value, use `key!=value`. This is converted behind the scenes to `key!~^value$`
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### If key is present
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This implies that, to check if a key is present, `key!=` can be used. This will only match if the key is present and not empty.
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Regex equals
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------------
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A tag can also be tested against a regex with `key~regex`. Note that this regex __must match__ the entire value. If the value is allowed to appear anywhere as substring, use `key~.*regex.*`
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Equivalently, `key!~regex` can be used if you _don't_ want to match the regex in order to appear.
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Using other tags as variables
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-----------------------------
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**This is an advanced feature - use with caution**
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Some tags are automatically set or calculated - see [CalculatedTags](CalculatedTags.md) for an entire overview.
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If one wants to apply such a value as tag, use a substituting-tag such, for example`survey:date:={_date:now}`. Note that the separator between key and value here is `:=`.
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The text between `{` and `}` is interpreted as a key, and the respective value is substituted into the string.
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One can also append, e.g. `key:={some_key} fixed text {some_other_key}`.
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An assigning tag _cannot_ be used to query OpenStreetMap/Overpass.
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If using a key or variable which might not be defined, add a condition in the mapping to hide the option.
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This is because, if `some_other_key` is not defined, one might actually upload the literal text `key={some_other_key}` to OSM - which we do not want.
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To mitigate this, use:
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```
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"mappings": [
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{
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"if":"key:={some_other_key}"
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"then": "...",
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"hideInAnswer": "some_other_key="
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}
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]
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``` |