mirror of https://github.com/databricks/cli.git
88 lines
2.1 KiB
Go
88 lines
2.1 KiB
Go
package convert
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import (
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"reflect"
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"strings"
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"sync"
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)
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// structInfo holds the type information we need to efficiently
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// convert data from a [config.Value] to a Go struct.
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type structInfo struct {
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// Fields maps the JSON-name of the field to the field's index for use with [FieldByIndex].
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Fields map[string][]int
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}
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// structInfoCache caches type information.
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var structInfoCache = make(map[reflect.Type]structInfo)
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// structInfoCacheLock guards concurrent access to structInfoCache.
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var structInfoCacheLock sync.Mutex
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// getStructInfo returns the [structInfo] for the given type.
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// It lazily populates a cache, so the first call for a given
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// type is slower than subsequent calls for that same type.
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func getStructInfo(typ reflect.Type) structInfo {
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structInfoCacheLock.Lock()
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defer structInfoCacheLock.Unlock()
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si, ok := structInfoCache[typ]
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if !ok {
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si = buildStructInfo(typ)
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structInfoCache[typ] = si
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}
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return si
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}
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// buildStructInfo populates a new [structInfo] for the given type.
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func buildStructInfo(typ reflect.Type) structInfo {
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var out = structInfo{
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Fields: make(map[string][]int),
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}
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// Queue holds the indexes of the structs to visit.
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// It is initialized with a single empty slice to visit the top level struct.
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var queue [][]int = [][]int{{}}
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for i := 0; i < len(queue); i++ {
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prefix := queue[i]
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// Traverse embedded anonymous types (if prefix is non-empty).
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styp := typ
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if len(prefix) > 0 {
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styp = styp.FieldByIndex(prefix).Type
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}
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// Dereference pointer type.
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if styp.Kind() == reflect.Pointer {
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styp = styp.Elem()
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}
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nf := styp.NumField()
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for j := 0; j < nf; j++ {
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sf := styp.Field(j)
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// Recurse into anonymous fields.
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if sf.Anonymous {
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queue = append(queue, append(prefix, sf.Index...))
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continue
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}
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name, _, _ := strings.Cut(sf.Tag.Get("json"), ",")
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if name == "" || name == "-" {
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continue
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}
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// Top level fields always take precedence.
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// Therefore, if it is already set, we ignore it.
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if _, ok := out.Fields[name]; ok {
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continue
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}
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out.Fields[name] = append(prefix, sf.Index...)
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}
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}
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return out
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}
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