Alec Thomas
1bb0c0b4b2
Kong supports limited variable interpolation into help strings, enum lists and
default values.
Variables are in the form:
${<name>}
Variables are set with the `Vars(map[string]string)` option. Undefined
variable references in the grammar will result in an error at construction
time.
28 lines
623 B
Go
28 lines
623 B
Go
package kong
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import (
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"fmt"
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"regexp"
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)
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var interpolationRegex = regexp.MustCompile(`(\${[[:alpha:]_][[:word:]]*})|(\$)|([^$]+)`)
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// Interpolate variables from vars into s for substrings in the form ${var}.
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func interpolate(s string, vars map[string]string) (string, error) {
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out := ""
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matches := interpolationRegex.FindAllStringSubmatch(s, -1)
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for _, match := range matches {
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if match[1] != "" {
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name := match[1][2 : len(match[1])-1]
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value, ok := vars[name]
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if !ok {
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return "", fmt.Errorf("undefined variable ${%s}", name)
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}
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out += value
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} else {
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out += match[0]
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}
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}
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return out, nil
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}
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