This patch adds a feature, if enabled, will infer a value's type from
its default value no matter from where else the value is set. This is
particularly important when working with environment variables. For
example:
package main
import (
"fmt"
"os"
"github.com/spf13/viper"
)
func print(name string, val interface{}) {
fmt.Printf("%-15[1]s%-15[2]T%[2]v\n", name, val)
}
func main() {
viper.BindEnv("mykey", "MYPREFIX_MYKEY")
viper.SetDefault("mykey", []string{})
os.Setenv("MYPREFIX_MYKEY", "a b c")
v1 := viper.GetStringSlice("mykey")
v2 := viper.Get("mykey")
print("v1", v1)
print("v2", v2)
}
When this program is executed the following is emitted:
[0]akutz@pax:ex$ ./ex1
v1 []string [a b c]
v2 string a b c
[0]akutz@pax:ex$
You may wonder, why is this important? Just use the GetStringSlice
function. Well, it *becomes* important when dealing with marshaling.
If we update the above program to this:
package main
import (
"fmt"
"os"
"github.com/spf13/viper"
)
type Data struct {
MyKey []string
}
func print(name string, val interface{}) {
fmt.Printf("%-15[1]s%-15[2]T%[2]v\n", name, val)
}
func main() {
viper.BindEnv("mykey", "MYPREFIX_MYKEY")
viper.SetDefault("mykey", []string{})
os.Setenv("MYPREFIX_MYKEY", "a b c")
v1 := viper.GetStringSlice("mykey")
v2 := viper.Get("mykey")
print("v1", v1)
print("v2", v2)
d := &Data{}
viper.Marshal(d)
print("d.MyKey", d.MyKey)
}
Now we can see the issue when we execute the updated program:
[0]akutz@pax:ex$ ./ex2
v1 []string [a b c]
v2 string a b c
d.MyKey []string []
[0]akutz@pax:ex$
The marshalled data structure's field MyKey is empty when in fact it
should have a string slice equal to, in value, []string {"a", "b",
"c"}.
The problem is that viper's Marshal function calls AllSettings which
ultimately uses the Get function. The Get function does try to infer
the value's type, but it does so using the type of the value retrieved
using this logic:
Get has the behavior of returning the value associated with the
first place from where it is set. Viper will check in the
following order:
* override
* flag
* env
* config file
* key/value store
* default
While the above order is the one we want when retrieving the values,
this patch enables users to decide if it's the order they want to be
used when inferring a value's type. To that end the function
SetTypeByDefaultValue is introduced. When SetTypeByDefaultValue(true)
is called, a call to the Get function will now first check a key's
default value, if set, when inferring a value's type. This is
demonstrated using a modified version of the same program above:
package main
import (
"fmt"
"os"
"github.com/spf13/viper"
)
type Data struct {
MyKey []string
}
func print(name string, val interface{}) {
fmt.Printf("%-15[1]s%-15[2]T%[2]v\n", name, val)
}
func main() {
viper.BindEnv("mykey", "MYPREFIX_MYKEY")
viper.SetDefault("mykey", []string{})
os.Setenv("MYPREFIX_MYKEY", "a b c")
v1 := viper.GetStringSlice("mykey")
v2 := viper.Get("mykey")
print("v1", v1)
print("v2", v2)
d1 := &Data{}
viper.Marshal(d1)
print("d1.MyKey", d1.MyKey)
viper.SetTypeByDefaultValue(true)
d2 := &Data{}
viper.Marshal(d2)
print("d2.MyKey", d2.MyKey)
}
Now the following is emitted:
[0]akutz@pax:ex$ ./ex3
v1 []string [a b c]
v2 string a b c
d1.MyKey []string []
d2.MyKey []string [a b c]
[0]akutz@pax:ex$
Viper should not be searching for config.{json,toml,yaml,yml}
in the directory where the `hugo` executable binary is located,
i.e. do not try to look for e.g. $GOPATH/bin/config.toml or
/usr/local/bin/config.toml
Hi. Thanks for creating Viper, it's been very useful to me. I come from Ruby and .yaml is really never used there, .yml is the common extension. I verified online and it's valid known extension for Yaml files so I added it. I realized this when trying to use `config.yml` in a project and getting an error on my code. Does adding this makes sense? Pretty silly addition, but it did confuse me for a while to realize the error using my app on a server, so I think it's worth adding. Cheers.
This fixes the aliases in config files bug. Whenever we register an alias, if there is a value in
the config (or defaults or override) for the alias, we move that value to the new "real key".
Added a test for the bug, which fails without the changes and passes with the changes.
This also fixes a bug in Hugo, where specifying "Taxonomies" in your config file doesn't get recognized,
because Hugo aliases "Taxonomies" to "Indexes" which means that when the code does a Get("Taxnomies") it
got translated to Get("Indexes"), which didn't exist in the original config map.
Use like:
fetchCmd.Flags().Int("rsstimeout", 5, "Timeout (in min) for RSS retrival")
viper.BindPFlag("rsstimeout", fetchCmd.Flags().Lookup("rsstimeout"))
