cmd/cue: verify the JSON for equivalence in get_go_json_compat

We took the JSON from `cue export` and unmarshalled it into the Go type
to verify it is still compatible, but we did not actually check
that the values are unchanged. This might not be the case if we,
for example, dropped a key or changed one of the key values.

This also means that we don't need to do a Go json.Unmarshal check;
if Go's json.Marshal results in exactly the same bytes as `cue export`,
then it's safe to assume that json.Unmarshal would work too.

While here, make sure we use `cue vet` in concrete mode.

Signed-off-by: Daniel Martí <[email protected]>
Change-Id: Id488eddfba3120d5d8f443a10e008805954a0d9d
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1211575
TryBot-Result: CUEcueckoo <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>
Reviewed-by: Roger Peppe <[email protected]>

Author: mvdan

cmd/cue/cmd/testdata/script/get_go_json_compat.txtar

@@ -6,15 +6,13 @@ cmp decls/p_go_gen.cue decls/p_go_gen.cue.golden
 
 # Marshal via Go's encoding/json and validate with the generated CUE schema.
 exec go run ./marshal
-cp stdout go_marshal.json
-cmp go_marshal.json go_marshal.json.golden
-exec cue vet go_marshal.json schema.cue
+cmp stdout go_marshal.json
+exec cue vet -c schema.cue go_marshal.json
 
-# Export from CUE and Unmarshal via Go's encoding/json.
+# Export from CUE to verify that it results in the same JSON as Go did.
+# This helps catch if any of the keys have been dropped or their values changed.
 exec cue export ./decls
-cmp stdout cue_export.json.golden
-stdin stdout
-exec go run ./unmarshal
+cmp stdout go_marshal.json
 
 -- schema.cue --
 package schema
@@ -41,16 +39,6 @@ package decls
 		#ResetColor,
 	]
 }
--- go_marshal.json.golden --
-{"Duration":3000000000,"Strings":["\u001b[31mError:\u001b[0m","\u001b[0m"]}
--- cue_export.json.golden --
-{
-    "Duration": 3000000000,
-    "Strings": [
-        "\u001b[31mError:\u001b[0m",
-        "\u001b[0m"
-    ]
-}
 -- decls/p.go --
 package decls
 
@@ -102,33 +90,18 @@ func main() {
 			decls.ResetColor,
 		},
 	}
-	data, err := json.Marshal(r)
+	// Mimic the formatting of `cue export` to be able to compare bytes.
+	data, err := json.MarshalIndent(r, "", "    ")
 	if err != nil {
 		log.Fatal(err)
 	}
 	fmt.Printf("%s\n", data)
 }
--- unmarshal/main.go --
-package main
-
-import (
-	"encoding/json"
-	"io"
-	"os"
-	"fmt"
-	"log"
-
-	"mod.test/decls"
-)
-
-func main() {
-	data, err := io.ReadAll(os.Stdin)
-	if err != nil {
-		log.Fatal(err)
-	}
-	var r decls.Root
-	if err := json.Unmarshal(data, &r); err != nil {
-		log.Fatal(err)
-	}
-	fmt.Printf("%s\n", data)
+-- go_marshal.json --
+{
+    "Duration": 3000000000,
+    "Strings": [
+        "\u001b[31mError:\u001b[0m",
+        "\u001b[0m"
+    ]
 }