MaxGekk opened a new pull request #30183:
URL: https://github.com/apache/spark/pull/30183
# What changes were proposed in this pull request?
In the PR, I propose to improve the error message from `from_json` by
combining errors from all schema parsers:
- DataType.fromJson
- CatalystSqlParser.parseDataType
- CatalystSqlParser.parseTableSchema
Before the changes, `from_json` does not show error messages from the first
parser in the chain that could mislead users.
### Why are the changes needed?
Currently, `from_json` outputs the error message from the fallback schema
parser which can confuse end-users. For example:
```scala
val invalidJsonSchema = """{"fields": [{"a":123}], "type": "struct"}"""
df.select(from_json($"json", invalidJsonSchema, Map.empty[String,
String])).show()
```
The JSON schema has an issue in `{"a":123}` but the error message doesn't
point it out:
```
mismatched input '{' expecting {'ADD', 'AFTER', ...}(line 1, pos 0)
== SQL ==
{"fields": [{"a":123}], "type": "struct"}
^^^
org.apache.spark.sql.catalyst.parser.ParseException:
mismatched input '{' expecting {'ADD', 'AFTER', ... }(line 1, pos 0)
== SQL ==
{"fields": [{"a":123}], "type": "struct"}
^^^
```
### Does this PR introduce _any_ user-facing change?
Yes, after the changes for the example above:
```
Cannot parse the schema in JSON format: Failed to convert the JSON string
'{"a":123}' to a field.
Failed fallback parsing: Cannot parse the data type:
mismatched input '{' expecting {'ADD', 'AFTER', ...}(line 1, pos 0)
== SQL ==
{"fields": [{"a":123}], "type": "struct"}
^^^
Failed fallback parsing:
mismatched input '{' expecting {'ADD', 'AFTER', ...}(line 1, pos 0)
== SQL ==
{"fields": [{"a":123}], "type": "struct"}
^^^
```
### How was this patch tested?
- By existing tests suites like `JsonFunctionsSuite` and
`JsonExpressionsSuite`.
- Add new test to `JsonFunctionsSuite`.
- Re-gen results for `json-functions.sql`.
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