cmd/cue: add test case for embedded file error

This adds a test case showing how the embed file
error positions are hidden. The fix will come in the
next CL.

For #3320

Signed-off-by: Roger Peppe <[email protected]>
Change-Id: I02625658c9b3783eb6bc84d7135ebf2069d9c48f
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1198349
Unity-Result: CUE porcuepine <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>

cmd/cue/cmd/testdata/script/embed_file_err.txtar

@@ -0,0 +1,39 @@
+# Test what happens when there is an error an embedded file.
+# TODO the error should mention the name of the file where the error is.
+
+env CUE_EXPERIMENT=embed
+! exec cue vet
+cmp stderr want-stderr
+! exec cue export
+cmp stderr want-stderr
+! exec cue def
+cmp stderr want-stderr
+
+-- want-stderr --
+@embed: invalid string:
+    ./x.cue:5:6
+-- cue.mod/module.cue --
+module: "test.example"
+language: version: "v0.9.2"
+-- x.cue --
+@extern(embed)
+
+package x
+
+e: _ @embed(glob="*.json",type=jsonschema)
+
+-- schema.json --
+{
+  "$schema": "http://json-schema.org/draft-04/schema#",
+  "additionalProperties": false,
+  "id": "https://example.test/example",
+  "required": ["x"],
+  "title": "example jsonschema",
+  "type": "object",
+  "properties": {
+    "x": {
+      "description": true,
+      "type": "number"
+    }
+  }
+}