Introduce named mappings to template substitution #726
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…ithDefaultWhenAbsence` and `withRequired` functions * By directly using `Substitute` function, `Config` cannot pass further, thus not preserved Signed-off-by: Vigilans <[email protected]>
* Named mapping is enabled only when `Config.namedMappings` is provided, otherwise compatibility is kept Signed-off-by: Vigilans <[email protected]>
Signed-off-by: Vigilans <[email protected]>
* Support formats like `${mapping[key]:-defaultValue}` `${mapping[key]:+presenceValue}`
* Support detecting presence of key in a named mapping through `${mapping[key]?errorMessage}`
Signed-off-by: Vigilans <[email protected]>
Signed-off-by: Vigilans <[email protected]>
* So named mappings can use panic to report error Signed-off-by: Vigilans <[email protected]>
Signed-off-by: Vigilans <[email protected]>
Signed-off-by: Vigilans <[email protected]>
Signed-off-by: Vigilans <[email protected]>
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This PR adds support for named mappings's syntax
${name[key]}intemplatepackage.Named Mappings
By
Mapping, we mean a user-supplied function to lookup value from key:type Mapping func(string) (string, bool). In compose it is provided with environment lookup.A named mappings is a collection of
Mapping, indexed by name key. It allows temporarily switching to another mapping other than default during interpolation.Template Syntax
Named mapping are used with syntax
${name[key]}, where an alternativeMappingis retrieved by keyname, and looked up using keykey.It supports all functions in default mappings:
${name[key]:-default},${name[key]:+presence},${name[key]?error}.It also supports mapping key to be a templated value, e.g.
${env[DIR_${container[replica-index]}]}.