6 ms·

I am confused, when was YAML ever considered a superset of JSON? These are completely different serialization formats.

andreareina 2y ago
I don't remember if it was an official talking point, but "you can load json on a yaml parser and it'll read the same" is a claim I've seen around.
pletnes 2y ago
By many people, e.g https://learning.sap.com/learning-journeys/build-side-by-side-extensions-on-sap-btp/explaining-json-yaml_db8975cf-695d-4ac2-8704-a9795116140c https://learning.sap.com/learning-journeys/build-side-by-sid... But the yaml docs said it’s accidental https://yaml.org/spec/1.2.2/ https://yaml.org/spec/1.2.2/ «The YAML 1.18 specification was published in 2005. Around this time, the developers became aware of JSON9. By sheer coincidence, JSON was almost a complete subset of YAML (both syntactically and semantically).»
- zquestz 2y ago
  Thanks. Didn't realize anyone thought this. I checked the YAML docs when I saw this post, and it didn't seem like an official feature. The SAP article definitely states it, that's the first time I have seen it described that way.
  - pletnes 2y ago
    I’ve seen the claim around, and I actually believed it, to be honest. I found that article by googling. I guess it’s still true enough for many cases.
jmillikin 2y ago
I wrote a similar article two years ago, with some screenshots of people claiming YAML is a superset of JSON: https://john-millikin.com/json-is-not-a-yaml-subset https://john-millikin.com/json-is-not-a-yaml-subset It's one of those beliefs that seems like it should be true, but isn't for obscure technical reasons.
- jorams 2y ago
  Your post's remark about YAML 1.2 being opt-in with a "%YAML 1.2" directive is true for the parser you are using (LibYAML), but is not compliant with the 1.2 spec. The spec specifies it should assume 1.2 and 1.1 should be opt-in.
  - jmillikin 2y ago
    It's true for all of the parsers that I tested at the time, which covered a couple different languages (Ruby, Python, C, Haskell). It appears to still be true in at least Ruby and Python, which are probably the two most popular languages to write YAML-consuming programs in: $ irb -v irb 1.3.5 (2021-04-03) $ irb irb(main):001:0> require 'yaml' => true irb(main):002:0> YAML.load '{"a": 1e2}' => {"a"=>"1e2"} irb(main):003:0> and $ python3 Python 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> import yaml >>> yaml.safe_load('{"a": 1e2}') {'a': '1e2'} >>> -- > The spec specifies it should assume 1.2 and 1.1 should be opt-in. The spec for 1.2 says that, but that's the reason parsers can't upgrade to 1.2, because changing the default version will cause backwards-incompatible parsing changes. Without the version directive there's no way for the parser to know which version was intended, so it defaults to 1.1, so people writing YAML will write YAML 1.1 documents, because that's what the parsers expect. The only way YAML 1.2 is going to displace older versions is in a greenfield ecosystem that has all its tools using YAML 1.2 from the beginning, but that requires an author who both (1) cares a lot about parser correctness, and (2) wants to use YAML as a config syntax, which isn't a large population.
    - jorams 2y ago
      It is indeed true for LibYAML, which is used by Python, Ruby, and the Haskell yaml package. The majority of YAML implementations I've seen that aren't based on LibYAML implement 1.2. I'm pointing it out because it's highly implementation dependent.
trueismywork 2y ago
Official YAML spec says so.
sorcix 2y ago
The YAML 1.2 spec states: > YAML can therefore be viewed as a natural superset of JSON, offering improved human readability and a more complete information model.
- zquestz 2y ago
  However this wasn't really true till 1.2 if I am reading the spec correctly. Plus many parsers default to 1.1. =\
- jorams 2y ago
  The YAML 1.0 spec says no such thing, it doesn't even mention JSON. Neither does the YAML 1.1 spec. The YAML 1.2.0 and 1.2.1 specs do say exactly that. 1.2.2 no longer does, but it reiterates that the primary focus of YAML 1.2 was to make it a strict superset of JSON.
  - sorcix 2y ago
    You're right. I must have clicked the wrong link, the YAML 1.0 spec doesn't mention JSON. The quote was from 1.2, thanks for pointing that out!
xelxebar 2y ago
Not only does the spec say that, but it was an explicit goal of Ingy döt Net, the designer of YAML.

I don't remember if it was an official talking point, but "you can load json on a yaml parser and it'll read the same" is a claim I've seen around.

pletnes 2y ago

By many people, e.g https://learning.sap.com/learning-journeys/build-side-by-side-extensions-on-sap-btp/explaining-json-yaml_db8975cf-695d-4ac2-8704-a9795116140c https://learning.sap.com/learning-journeys/build-side-by-sid... But the yaml docs said it’s accidental https://yaml.org/spec/1.2.2/ https://yaml.org/spec/1.2.2/ «The YAML 1.18 specification was published in 2005. Around this time, the developers became aware of JSON9. By sheer coincidence, JSON was almost a complete subset of YAML (both syntactically and semantically).»

zquestz 2y ago
Thanks. Didn't realize anyone thought this. I checked the YAML docs when I saw this post, and it didn't seem like an official feature. The SAP article definitely states it, that's the first time I have seen it described that way.
- pletnes 2y ago
  I’ve seen the claim around, and I actually believed it, to be honest. I found that article by googling. I guess it’s still true enough for many cases.

jmillikin 2y ago

I wrote a similar article two years ago, with some screenshots of people claiming YAML is a superset of JSON: https://john-millikin.com/json-is-not-a-yaml-subset https://john-millikin.com/json-is-not-a-yaml-subset It's one of those beliefs that seems like it should be true, but isn't for obscure technical reasons.

jorams 2y ago
Your post's remark about YAML 1.2 being opt-in with a "%YAML 1.2" directive is true for the parser you are using (LibYAML), but is not compliant with the 1.2 spec. The spec specifies it should assume 1.2 and 1.1 should be opt-in.
- jmillikin 2y ago
  It's true for all of the parsers that I tested at the time, which covered a couple different languages (Ruby, Python, C, Haskell). It appears to still be true in at least Ruby and Python, which are probably the two most popular languages to write YAML-consuming programs in: $ irb -v irb 1.3.5 (2021-04-03) $ irb irb(main):001:0> require 'yaml' => true irb(main):002:0> YAML.load '{"a": 1e2}' => {"a"=>"1e2"} irb(main):003:0> and $ python3 Python 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> import yaml >>> yaml.safe_load('{"a": 1e2}') {'a': '1e2'} >>> -- > The spec specifies it should assume 1.2 and 1.1 should be opt-in. The spec for 1.2 says that, but that's the reason parsers can't upgrade to 1.2, because changing the default version will cause backwards-incompatible parsing changes. Without the version directive there's no way for the parser to know which version was intended, so it defaults to 1.1, so people writing YAML will write YAML 1.1 documents, because that's what the parsers expect. The only way YAML 1.2 is going to displace older versions is in a greenfield ecosystem that has all its tools using YAML 1.2 from the beginning, but that requires an author who both (1) cares a lot about parser correctness, and (2) wants to use YAML as a config syntax, which isn't a large population.
  - jorams 2y ago
    It is indeed true for LibYAML, which is used by Python, Ruby, and the Haskell yaml package. The majority of YAML implementations I've seen that aren't based on LibYAML implement 1.2. I'm pointing it out because it's highly implementation dependent.

trueismywork 2y ago

Official YAML spec says so.

sorcix 2y ago

The YAML 1.2 spec states: > YAML can therefore be viewed as a natural superset of JSON, offering improved human readability and a more complete information model.

zquestz 2y ago
However this wasn't really true till 1.2 if I am reading the spec correctly. Plus many parsers default to 1.1. =\
jorams 2y ago
The YAML 1.0 spec says no such thing, it doesn't even mention JSON. Neither does the YAML 1.1 spec. The YAML 1.2.0 and 1.2.1 specs do say exactly that. 1.2.2 no longer does, but it reiterates that the primary focus of YAML 1.2 was to make it a strict superset of JSON.
- sorcix 2y ago
  You're right. I must have clicked the wrong link, the YAML 1.0 spec doesn't mention JSON. The quote was from 1.2, thanks for pointing that out!

xelxebar 2y ago

Not only does the spec say that, but it was an explicit goal of Ingy döt Net, the designer of YAML.