Combining multiple JSON files by using file metadata | CUE

Jonathan Matthews

This Commented CUE demonstrates how to use the cue command to combine multiple JSON files by making reference to the files’ metadata.

The TERMINAL section shows the use of:

the --with-context parameter, which makes information about each input file available as metadata
the filename metadata field combined with the -l parameter, which places each file’s contents at an individual and deterministic location in the evaluation space

{
    "a": 1,
    "b": 2,
    "c": 3
}

{
    "a": "a string",
    "b": true,
    "c": 42
}

[
    "a list element",
    "another element",
    "the last element"
]

package example

// inputs is the location under which we place
// each data file's contents, so that their
// contents can be accessed by the CUE in this
// file. The cue CLI -l parameter places them
// here, under a secondary key determined by each
// file's name.
inputs: [string]: _

output: {
	for _name, _content in inputs {
		(_name): {
			filename: _name
			content:  _content
		}
	}
}

$ cue export --with-context -l 'inputs:' -l 'path.Base(filename)' -e output a.json b.json c.json example.cue
{
    "a.json": {
        "filename": "a.json",
        "content": {
            "a": 1,
            "b": 2,
            "c": 3
        }
    },
    "b.json": {
        "filename": "b.json",
        "content": {
            "a": "a string",
            "b": true,
            "c": 42
        }
    },
    "c.json": {
        "filename": "c.json",
        "content": [
            "a list element",
            "another element",
            "the last element"
        ]
    }
}

How-to Guide: Combining multiple YAML files by using file metadata
Reference: cue help flags documents the --with-context and -l flags

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