fix -Zast-json to output correct JSON form

[JOE1994]

fixes#71086 (Reverts some of the changes made in #70215)

JSON output (from an empty library) after fix has something for "id" field

lonelyjoe@lonelyjoe-desktop:~/workspace/empty_lib/src$ rustc lib.rs -Zast-json

{
"module":{
"inner":{
"lo":0,
"hi":94
},
"items":[
{
"attrs":[
{
"kind":{
"variant":"Normal",
"fields":[
{
"path":{
"span":{
"lo":0,
"hi":0
},
"segments":[
{
"ident":{
"name":"prelude_import",
"span":{
"lo":0,
"hi":0
}
},
"id":3,
"args":null
}
]
},
"args":"Empty"
}
]
},
"id":null,
"style":"Outer",
"span":{
"lo":0,
"hi":0
}
}
],
"id":4,
"span":{
"lo":0,
"hi":0
},
"vis":{
"node":"Inherited",
"span":{
"lo":0,
"hi":0
}
},
"ident":{
"name":"",
"span":{
"lo":0,
"hi":0
}
},
"kind":{
"variant":"Use",
"fields":[
{
"prefix":{
"span":{
"lo":0,
"hi":0
},
"segments":[
{
"ident":{
"name":"{{root}}",
"span":{
"lo":0,
"hi":0
}
},
"id":5,
"args":null
},
{
"ident":{
"name":"std",
"span":{
"lo":0,
"hi":0
}
},
"id":6,
"args":null
},
{
"ident":{
"name":"prelude",
"span":{
"lo":0,
"hi":0
}
},
"id":7,
"args":null
},
{
"ident":{
"name":"v1",
"span":{
"lo":0,
"hi":0
}
},
"id":8,
"args":null
}
]
},
"kind":"Glob",
"span":{
"lo":0,
"hi":0
}
}
]
},
"tokens":null
},
{
"attrs":[
{
"kind":{
"variant":"Normal",
"fields":[
{
"path":{
"span":{
"lo":0,
"hi":0
},
"segments":[
{
"ident":{
"name":"macro_use",
"span":{
"lo":0,
"hi":0
}
},
"id":9,
"args":null
}
]
},
"args":"Empty"
}
]
},
"id":null,
"style":"Outer",
"span":{
"lo":0,
"hi":0
}
}
],
"id":10,
"span":{
"lo":0,
"hi":0
},
"vis":{
"node":"Inherited",
"span":{
"lo":0,
"hi":0
}
},
"ident":{
"name":"std",
"span":{
"lo":0,
"hi":0
}
},
"kind":{
"variant":"ExternCrate",
"fields":[
null
]
},
"tokens":null
}
],
"inline":true
},
"attrs":[
],
"span":{
"lo":0,
"hi":94
},
"proc_macros":[
]
}

[rust-highfive]

r? @estebank

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[JOE1994]

r? @petrochenkov

[petrochenkov]

@JOE1994
Could you revert the change to Decodable as well to keep encoding and decoding symmetric?
(Decoding is probably not used for json specifically, but anyway.)

[petrochenkov]

There's a test src\test\ui\ast-json\ast-json-output.rs using -Z ast-json.
Could you add an attribute to it so the output contains "id":null?

[JOE1994]

There's a test src\test\ui\ast-json\ast-json-output.rs using -Z ast-json.
Could you add an attribute to it so the output contains "id":null?

Thank you for your feedback! 👍 It seems that src/test/ui/ast-json/ast-json-output.rs only tests the stdout of -Z ast-json-noexpand and not -Z ast-json. The test was successful regardless of the changes made in this PR.

Below is what I thought I might have to do here (not yet committed):

1. Rename the following files

• src/test/ui/ast-json/ast-json-output.rs -> src/test/ui/ast-json/ast-json-noexpand.rs
• src/test/ui/ast-json/ast-json-output.stdout -> src/test/ui/ast-json/ast-json-noexpand.stdout

2. Create new test files (to test output of -Z ast-json)

• src/test/ui/ast-json/ast-json-output.rs
• src/test/ui/ast-json/ast-json-output.stdout

May I ask how I can add an attribute to allow the test to contain "id:null"?
It seems that the current test simply compares the stdout with the provided existing file (src/test/ui/ast-json/ast-json.stdout).

[JOE1994]

I referred to the rustc-guide secion on rustc tests but couldn't find info on adding attributes to tests 😿

[petrochenkov]

@JOE1994
I think any attribute will work, e.g. #[inline] on the main function.

Having separate tests for -Z ast-json and -Z ast-json-noexpand would be nice.

[petrochenkov]

Thanks!
@bors r+

[bors]

📌 Commit b469d2d has been approved by petrochenkov