Support Arrays of Tables

[NfNitLoop]

I see this is already called out as a feature that's not yet implemented in the README:

❌ Array of Tables

I just wanted to make a ticket for it so folks can vote for it, and so I can get notified when it's implemented. (It's currently a blocker for my use case.)

---

My use case is this:

I want to support multiple configuration environments in one file. Like:

[[environments]]
name = "foo"
# …

[[environments]]
name = "bar"
# …

But that currently gives an error:

Not able to parse the key: [[environments]] as it contains invalid symbols. In case you would like to use special symbols - use quotes as it is required by TOML standard: "My key ~ with special % symbols"

---

Alternatively, I also tried a "Map of Tables" approach like this, but that didn't work either:

[environments.foo]
# …

[environments.bar]
# …

Error:

Invalid number of key-value arguments provided in the input for deserialization. Missing the required field <0> from class <kotlin.collections.LinkedHashMap> in the input

[orchestr7]

@NfNitLoop Thank you for this issue, I will pin it. I actually planned to start from it right now :)

[orchestr7]

A link for the SPEC: https://toml.io/en/v1.0.0#inline-table

What should we pay attention on:

1. nested array of tables (may be later)
2. If the parent of a table or array of tables is an array element, that element must already have been defined before the child can be defined (not sure if this is really needed):

# INVALID TOML DOC
[fruit.physical]  # subtable, but to which parent element should it belong?
color = "red"
shape = "round"

[[fruit]]  # parser must throw an error upon discovering that "fruit" is
           # an array rather than a table
name = "apple"

3. Attempting to append to a statically defined array, even if that array is empty, must produce an error at parse time:

# INVALID TOML DOC
fruits = []

[[fruits]] # Not allowed

4. Attempting to define a normal table with the same name as an already established array must produce an error at parse time. Attempting to redefine a normal table as an array must likewise produce a parse-time error.

[orchestr7]

Difficult part here is to understand how to represent such structure in a tree.

I suppose that we need to do the following:

1. If the trimmed string starts with ''Parse [[ ]] and put it to some ArrayTableNode that will contain children TableNode
2. each time we will append a TableNode to such array

[orchestr7]

Finally added the support for parsing of arrays of tables: #104
Next step is to make the decoding

[bishiboosh]

@akuleshov7 so what's still missing for array of tables to work ?

[orchestr7]

@akuleshov7 so what's still missing for array of tables to work ?

decoding process. I have added parsing, added tree structures, only decoding is missing now

[Wavesonics]

@akuleshov7 any progress on decoding these? Just ran into this in my project

[sschuberth]

I'm interested in parsing cargo.lock files, see e.g. this. Am I correct to assume that this issue would need to get resolved for that first?

[orchestr7]

I'm interested in parsing cargo.lock files, see e.g. this. Am I correct to assume that this issue would need to get resolved for that first?

Oh, I missed that question, sorry. Yes, this is a blocker and we will take it as the highest priority. As I didn't know that Cargo has arrays of tables. Will take it into 0.6.0 release, as previously we thought that multiline arrays/strings and streaming had more priority and were focused on that.

This one is a very long story and I hope to finish it in the nearest months.

[sschuberth]

Will take it into 0.6.0 release

Thanks for prioritizing this!

[kubeliv]

I am also patiently waiting for this feature! 🙂

[severinsch]

This is also a blocker for my use case, can you provide a rough timeline on when we can expect the new release?
🙏

[orchestr7]

This is also a blocker for my use case, can you provide a rough timeline on when we can expect the new release?
🙏

ktoml is community project, driven only by several people, so probably there are some time difficulties in supporting it. But you can also contribute and collaborate if it is a hard stopper for you, we will appreciate it 🙏

My personal estimation was to make it last month, but still did not get a chance for it. I will be on vacation next week, so probably I will give it a try…

[orchestr7]

related issues:
#259
#254
#231

[mgroth0]

For anyone who needs this, I think a temporary workaround is to use TomlJ to convert the toml to json and then decode as json. Theoretically this should be very simple to swap for ktoml once it is ready.