v2ray-core/main/commands/all/merge_doc.go

package all

import (
	"github.com/v2fly/v2ray-core/v4/main/commands/base"
)

var docMerge = &base.Command{
	UsageLine: "{{.Exec}} config-merge",
	Short:     "config merge logic",
	Long: `
Merging of config files is applied in following commands:

	{{.Exec}} run -c c1.json -c c2.json ...
	{{.Exec}} test -c c1.yaml -c c2.yaml ...
	{{.Exec}} convert c1.json dir1 ...

Support of yaml is implemented by converting yaml to json, 
both merge and load. So we take json as example here.

Suppose we have 2 JSON files,

The 1st one:

	{
	  "log": {"access": "some_value", "loglevel": "debug"},
	  "inbounds": [{"tag": "in-1"}],
	  "outbounds": [{"_priority": 100, "tag": "out-1"}],
	  "routing": {"rules": [
		{"_tag":"default_route","inboundTag":["in-1"],"outboundTag":"out-1"}
	  ]}
	}

The 2nd one:

	{
	  "log": {"loglevel": "error"},
	  "inbounds": [{"tag": "in-2"}],
	  "outbounds": [{"_priority": -100, "tag": "out-2"}],
	  "routing": {"rules": [
		{"inboundTag":["in-2"],"outboundTag":"out-2"},
		{"_tag":"default_route","inboundTag":["in-1.1"],"outboundTag":"out-1.1"}
	  ]}
	}

Output:

	{
	  // loglevel is overwritten
	  "log": {"access": "some_value", "loglevel": "error"},
	  "inbounds": [{"tag": "in-1"}, {"tag": "in-2"}],
	  "outbounds": [
		{"tag": "out-2"}, // note the order is affected by priority
		{"tag": "out-1"}
	  ],
	  "routing": {"rules": [
		// note 3 rules are merged into 2, and outboundTag is overwritten,
		// because 2 of them has same tag
		{"inboundTag":["in-1","in-1.1"],"outboundTag":"out-1.1"}
		{"inboundTag":["in-2"],"outboundTag":"out-2"}
	  ]}
	}

Explained: 

- Simple values (string, number, boolean) are overwritten, others are merged
- Elements with same "tag" (or "_tag") in an array will be merged
- Add "_priority" property to array elements will help sort the array
`,
}