JsonPath=$ causes ClassCastException

[greg-at-moderne]

What version of OpenRewrite are you using?

Current main (4684213)

Minimal example

The following test in JsonPathMatcherTest:

    @Test
    void dollarToMatchTheRoot() {
        assertMatched("$", simple, simple);
    }

fails with:

line 1:1 mismatched input '<EOF>' expecting {'[', '.', '..'}

org.openrewrite.internal.RecipeRunException: java.lang.ClassCastException: class org.antlr.v4.runtime.tree.TerminalNodeImpl cannot be cast to class org.openrewrite.json.internal.grammar.JsonPathParser$ExpressionContext (org.antlr.v4.runtime.tree.TerminalNodeImpl and org.openrewrite.json.internal.grammar.JsonPathParser$ExpressionContext are in unnamed module of loader 'app')

	at org.openrewrite.TreeVisitor.visit(TreeVisitor.java:290)
[...]
Caused by: java.lang.ClassCastException: class org.antlr.v4.runtime.tree.TerminalNodeImpl cannot be cast to class org.openrewrite.json.internal.grammar.JsonPathParser$ExpressionContext (org.antlr.v4.runtime.tree.TerminalNodeImpl and org.openrewrite.json.internal.grammar.JsonPathParser$ExpressionContext are in unnamed module of loader 'app')
	at org.openrewrite.json.JsonPathMatcher.find0(JsonPathMatcher.java:76)
	at org.openrewrite.json.JsonPathMatcher.matches(JsonPathMatcher.java:86)
	at org.openrewrite.json.JsonPathMatcherTest$2.visitLiteral(JsonPathMatcherTest.java:914)
	at org.openrewrite.json.JsonPathMatcherTest$2.visitLiteral(JsonPathMatcherTest.java:864)
	at org.openrewrite.json.tree.Json$Literal.acceptJson(Json.java:253)
	at org.openrewrite.json.tree.Json.accept(Json.java:39)
	at org.openrewrite.TreeVisitor.visit(TreeVisitor.java:250)
	... 28 more

Broader context

• JsonPath is used as an argument to multiple recipes for languages like JSON or YAML
• AFAICT $ is a valid JsonPath expression to denote the root of the document and it should be supported
• e.g.

  rewrite/rewrite-json/src/test/java/org/openrewrite/json/AddKeyValueTest.java

  Line 30 in bf0519d

  spec -> spec.recipe(new AddKeyValue("$.", "key", "\"val\"", false)),

  uses $. (which BTW I think is invalid JsonPath), if you put $ there you get the same ClassCastException.
• in some contexts the exception is wrapped/handled and the only thing you can see is a warning:

line 1:2 mismatched input '<EOF>' expecting {'[', '*', Identifier, StringLiteral}

[greg-at-moderne]

Labelling as parser-json as the "closest relative" of JsonPath. The problem likely affects HCL and YAML too.

[Jenson3210]

I can confirm this is also showing in the MergeYaml recipe -> was able to bypass the error by using $.. Strangely enough, when I run the tests that execute the MergeYaml directly, there it is working. (there are even existing tests)
When i run the tests that run a recipe that internally calls MergeYaml, it is not working with this exception.

[traceyyoshima]

I don't have time to check if any changes will be needed down stream, but this issue stems from the ANTLR grammar. This should be a quick fix.

jsonPath
    : ROOT | (ROOT? expression+)
    ;

[greg-at-moderne]

Correct, @traceyyoshima.
I already have it in flight.

EDIT two months later: After applying the $ change to the grammar, some errors popped up. Needs to be investigated.