encoding/openapi: fix crash in reference

For certain values, inst could be nil, even though there were
references. The code in OpenAPI was a workaround around
references, though, and seems no longer necessary.

Fixes #1270

Signed-off-by: Marcel van Lohuizen <mpvl@golang.org>

Change-Id: Ie2a9d0a5ddc669f77e21fd5d2128341613c6510a
Signed-off-by: Marcel van Lohuizen <mpvl@golang.org>
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/527871
Unity-Result: CUEcueckoo <cueckoo@cuelang.org>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Paul Jolly <paul@myitcv.io>

Author: mpvl

cmd/cue/cmd/testdata/script/issue1270.txt

@@ -0,0 +1,41 @@
+cue def test.cue test.json -o openapi:- -e '{#Output: #Test}'
+
+cmp stdout stdout.golden
+
+-- test.cue --
+#Int: int
+#Test: test: #Int
+
+-- test.json --
+{ }
+
+-- stdout.golden --
+{
+    "openapi": "3.0.0",
+    "info": {
+        "title": "Generated by cue.",
+        "version": "no version"
+    },
+    "paths": {},
+    "components": {
+        "schemas": {
+            "Int": {
+                "type": "integer"
+            },
+            "Output": {
+                "$ref": "#/components/schemas/Test"
+            },
+            "Test": {
+                "type": "object",
+                "required": [
+                    "test"
+                ],
+                "properties": {
+                    "test": {
+                        "$ref": "#/components/schemas/Int"
+                    }
+                }
+            }
+        }
+    }
+}

encoding/openapi/types.go

@@ -16,7 +16,6 @@ package openapi
 
 import (
 	"fmt"
-	"strings"
 
 	"github.com/cockroachdb/apd/v2"
 
@@ -58,21 +57,17 @@ func extractFormat(v cue.Value) string {
 	default:
 		return ""
 	}
-	var expr, arg string
-	op, a := v.Expr()
-	if op == cue.CallOp {
+	var arg string
+
+	if op, a := v.Expr(); op == cue.CallOp {
 		v = a[0]
 		if len(a) == 2 {
 			arg = fmt.Sprintf(" (%v)", a[1].Eval())
 		}
 	}
-	if inst, ref := v.Reference(); len(ref) > 0 {
-		expr = inst.ImportPath + "." + strings.Join(ref, ".")
-		expr += arg
-	} else {
-		expr = fmt.Sprint(v.Eval())
-		expr += arg
-	}
+
+	expr := fmt.Sprint(v.Eval(), arg)
+
 	if s, ok := cueToOpenAPI[expr]; ok {
 		return s
 	}