How do I skip document with errors in YAML stream? - parsing

Question

It does not appear that the Python library pyyaml will allow me to read a multi-document YAML stream and continue past the point of an parsing error. I have two related questions:
Am I just missing something, and some other API will support this?
Do parsers in other programming languages support this operation? (if so, which)
Here is an example of a multiple-document YAML stream:
%YAML 1.1
---
# YAML can contain comments like this
name: David
age: 55
---
name: Mei
age: 50 # Including end-of-line
---
name: Juana: ERROR
age: 47
...
---
name: Adebayo
age: 58
...
I would like code similar to this to skip the bad document, but figure out "no matter how bad this document is, something new starts after the ... and ---.
with open('data/multidoc-bad.yaml') as stream:
docs = yaml.load_all(stream)
while True:
try:
doc = next(docs)
print(doc)
except StopIteration:
break
except Exception as err:
print(err)
I'd like to get:
{'name': 'David', 'age': 55}
{'name': 'Mei', 'age': 50}
mapping values are not allowed here
in "data/multidoc-bad.yaml", line 10, column 12
{'name': 'Adebayo', 'age': 58}
But in reality I do not get that last line for "Adebayo."
I recognize that I could write a small parser myself that reads lines and only looks for ... and --- lines to chunk the stream. Then pass only single documents to yaml.loads() after my own parsing. But it sure seems like that's what a parser is supposed to do for me.

Answer 1

Am I just missing something, and some other API will support this?
No, PyYAML cannot do this.
Do parsers in other programming languages support this operation? (if so, which)
None that I know of. Most YAML parsers are hand-written with quite some being translations from PyYAML. I don't know a single one that implements error recovery. (I worked with SnakeYAML, go-yaml, PyYAML, libyaml, YamlDotNet, and authored NimYAML and AdaYaml.)
But it sure seems like that's what a parser is supposed to do for me.
I think the reasons why parsers don't support this include
writing a compliant parser for YAML is already very complex without error recovery,
the multi-document feature is seldom used and therefore little effort is put into enhancing it,
this is the only case where it is obvious how to implement error recovery; I would argue that inside a YAML document, it is nigh impossible to implement useful error recovery, and therefore error recovery is not seen as an obvious feature to implement,
the workaround is very simple (you described it yourself).