Strict parsing

[ghost]

Is there a way to instruct toml to fail if any key=value pair associated to a struct field is not present in the config file?

The reason I ask is because toml.DecodeFile() does not warn you when a key=value pair is missing, and using md.IsDefined() for each key is not mantainable in large config files.

If the feature is not present, would you consider adding it in the future? Having guarantees about the config file completeness is a big deal.

[arp242]

I looked a bit at this, and adding this is possible but non-trivial.

I'm also not sure how common this use case necessarily is; certainly most config files I'm familiar with don't need every single key to be set, if there are keys that are required to be set then it's usually only a subset. And should we could all exported struct fields or only those with a toml tag set? Different people probably want different things.

And most importantly: this is a use case that can already be solved by checking meta.Keys(), which lists all keys that were encountered in the TOML file. For example:

var s struct {
	A int `toml:"a"`
}
file := `
	a = 42
	[tbl]
	a = 43`
meta, _ := toml.Decode(file, &s)
fmt.Printf("Keys: %q; Undecoded: %q\n", meta.Keys(), meta.Undecoded())

Prints:

Keys: ["a" "tbl" "tbl.a"]; Undecoded: ["tbl" "tbl.a"]

You can check if Keys() contains what you want. This is flexible for all use cases, and pretty much the reason the Meta object exists.

Unless there are serious practical problems with this, I think adding this is too much effort for too little benefit. But feel free to comment with more information/use cases and we can look and possibly reopen.