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encoding/yaml: decode empty YAML files as `*null | _`
This allows empty YAML files to be loaded with non-empty YAML files,
which usually decode as structs, without resulting in conflicts.
The default allows the loading of a single empty YAML file to still
result in a concrete `null` value, which is desirable.
Thanks to Roger for coming up with the disjunction idea.
Fixes #3744.
Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: I9a2c4d9ec45af6ff080ffa25ad07ac913552cdc1
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1211360
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-by: Roger Peppe <rogpeppe@gmail.com>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
+32
-18
+7
-7
cmd/cue/cmd/testdata/script/empty_yaml.txtar
+7
-7
cmd/cue/cmd/testdata/script/empty_yaml.txtar
···
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# Empty YAML files by themselves decode as null, following the YAML spec.
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# However, for the sake of the user experience when joining with other YAML files,
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# we allow unifying with them as well. This is done by decoding empty YAML as `*null | _`.
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# TODO: implement the above and make the second test case below work.
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exec cue export empty.yaml
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cmp stdout export-empty.stdout
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! exec cue export one.yaml empty.yaml two.yaml
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cmp stderr export-all.stderr
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exec cue export one.yaml empty.yaml two.yaml
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cmp stdout export-all.stdout
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-- export-empty.stdout --
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null
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-- export-all.stderr --
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conflicting values null and {two:"two text"} (mismatched types null and struct):
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./empty.yaml
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./two.yaml:1:1
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-- export-all.stdout --
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{
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"one": "one text",
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"two": "two text"
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}
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-- one.yaml --
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one: "one text"
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-- empty.yaml --
+1
-1
cmd/cue/cmd/testdata/script/import_list.txtar
+1
-1
cmd/cue/cmd/testdata/script/import_list.txtar
+2
-2
encoding/yaml/yaml_test.go
+2
-2
encoding/yaml/yaml_test.go
+19
-5
internal/encoding/yaml/decode.go
+19
-5
internal/encoding/yaml/decode.go
···
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// Any further Decode calls must return EOF to avoid an endless loop.
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d.decodeErr = io.EOF
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// If the input is empty, we produce a single null literal with EOF.
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// If the input is empty, we produce `*null | _` followed by EOF.
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// Note that when the input contains "---", we get an empty document
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// with a null scalar value inside instead.
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if !d.yamlNonEmpty {
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return &ast.BasicLit{
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Kind: token.NULL,
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ValuePos: d.tokFile.Pos(0, token.NoRelPos),
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Value: "null",
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// Attach positions which at least point to the filename.
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pos := d.tokFile.Pos(0, token.NoRelPos)
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return &ast.BinaryExpr{
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Op: token.OR,
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OpPos: pos,
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X: &ast.UnaryExpr{
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Op: token.MUL,
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OpPos: pos,
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X: &ast.BasicLit{
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Kind: token.NULL,
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ValuePos: pos,
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Value: "null",
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},
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},
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Y: &ast.Ident{
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Name: "_",
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NamePos: pos,
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},
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}, nil
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}
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// If the input wasn't empty, we already decoded some CUE syntax nodes,
+2
-2
internal/encoding/yaml/decode_test.go
+2
-2
internal/encoding/yaml/decode_test.go