internal/core/adt: add compatibility mode for issue 3534

The OpenInline compatibility mode was previously
added to allow ignoring closedness errors when
selecting into an inline struct.

V2, however, in addition to allowing such errors, would
also recursively open up definitions. This change
simulates that behavior when OpenInline is enabled by
treating the result of selecting into an inline struct
as an embedding.

Note that this is an orthogonal construct to the one
previously introduced with OpenInline. Because they
are highly related, however, we will enabled them
under the same option.

Note that the introduced mechanism also opens up
calls to close. This was not the case in V2.
This will hopefully not cause any issues in the
transition and, given that this is a temporary
measure, also not cause issues down the line.

Fixes #3534

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: I256fcdc7dd7c1b859cafa566b2bf396de9539f09
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1204736
Unity-Result: CUE porcuepine <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

Author: mpvl

cue/testdata/eval/openinline.txtar

@@ -88,14 +88,6 @@ Conjuncts:    141
 Disjuncts:    107
 -- out/evalalpha --
 Errors:
-outerErr.extraNesting.t1.version.x.major: field not allowed:
-    ./in.cue:46:25
-outerErr.issue3534.t1.version.major: field not allowed:
-    ./in.cue:19:8
-    ./in.cue:25:22
-outerErr.usingClose.t1.version.major: field not allowed:
-    ./in.cue:34:17
-    ./in.cue:35:22
 #E.b: field not allowed:
     ./in.cue:57:14
     ./cue.mod/pkg/foo.com/example/example.cue:4:11
@@ -114,17 +106,15 @@ Result:
       x: (int){ 2 }
     }
   }
-  outerErr: (_|_){
-    // [eval]
+  outerErr: (struct){
     _inToOut: (struct){
       in: (_){ _ }
       out: (_|_){
         // [incomplete] outerErr._inToOut.out: in.foo undefined as in is incomplete (type _):
         //     ./in.cue:19:8
       }
     }
-    issue3534: (_|_){
-      // [eval]
+    issue3534: (struct){
       #Inner: (#struct){
         foo: (#struct){
           minor: (int){ 2 }
@@ -135,21 +125,14 @@ Result:
           major: (int){ 1 }
         }
       }
-      t1: (_|_){
-        // [eval]
-        version: (_|_){
-          // [eval]
-          major: (_|_){
-            // [eval] outerErr.issue3534.t1.version.major: field not allowed:
-            //     ./in.cue:19:8
-            //     ./in.cue:25:22
-          }
+      t1: (#struct){
+        version: (#struct){
+          major: (int){ 1 }
           minor: (int){ 2 }
         }
       }
     }
-    usingClose: (_|_){
-      // [eval]
+    usingClose: (struct){
       #Inner: (#struct){
         foo: (#struct){
           minor: (int){ 2 }
@@ -160,21 +143,14 @@ Result:
           major: (int){ 1 }
         }
       }
-      t1: (_|_){
-        // [eval]
-        version: (_|_){
-          // [eval]
-          major: (_|_){
-            // [eval] outerErr.usingClose.t1.version.major: field not allowed:
-            //     ./in.cue:34:17
-            //     ./in.cue:35:22
-          }
+      t1: (#struct){
+        version: (#struct){
+          major: (int){ 1 }
           minor: (int){ 2 }
         }
       }
     }
-    extraNesting: (_|_){
-      // [eval]
+    extraNesting: (struct){
       #Inner: (#struct){
         foo: (#struct){
           x: (#struct){
@@ -189,16 +165,10 @@ Result:
           }
         }
       }
-      t1: (_|_){
-        // [eval]
-        version: (_|_){
-          // [eval]
-          x: (_|_){
-            // [eval]
-            major: (_|_){
-              // [eval] outerErr.extraNesting.t1.version.x.major: field not allowed:
-              //     ./in.cue:46:25
-            }
+      t1: (#struct){
+        version: (#struct){
+          x: (#struct){
+            major: (int){ 1 }
             minor: (int){ 2 }
           }
         }
@@ -238,18 +208,12 @@ Result:
 diff old new
 --- old
 +++ new
-@@ -1,10 +1,18 @@
+@@ -1,10 +1,10 @@
  Errors:
 -outerErr.usingClose.t1.version.major: field not allowed:
-+outerErr.extraNesting.t1.version.x.major: field not allowed:
-+    ./in.cue:46:25
-+outerErr.issue3534.t1.version.major: field not allowed:
-     ./in.cue:19:8
+-    ./in.cue:19:8
 -    ./in.cue:34:23
-+    ./in.cue:25:22
-+outerErr.usingClose.t1.version.major: field not allowed:
-+    ./in.cue:34:17
-     ./in.cue:35:22
+-    ./in.cue:35:22
 -    ./in.cue:37:7
 -    ./in.cue:38:16
 +#E.b: field not allowed:
@@ -261,11 +225,22 @@ diff old new
 
  Result:
  (_|_){
-@@ -26,20 +34,27 @@
-         //     ./in.cue:19:8
+@@ -17,8 +17,7 @@
+       x: (int){ 2 }
+     }
+   }
+-  outerErr: (_|_){
+-    // [eval]
++  outerErr: (struct){
+     _inToOut: (struct){
+       in: (_){ _ }
+       out: (_|_){
+@@ -44,30 +43,20 @@
+         }
        }
      }
--    issue3534: (struct){
+-    usingClose: (_|_){
+-      // [eval]
 -      #Inner: (#struct){
 -        foo: (#struct){
 -          minor: (int){ 2 }
@@ -276,11 +251,19 @@ diff old new
 -          major: (int){ 1 }
 -        }
 -      }
--      t1: (#struct){
--        version: (#struct){
--          major: (int){ 1 }
-+    issue3534: (_|_){
-+      // [eval]
+-      t1: (_|_){
+-        // [eval]
+-        version: (_|_){
+-          // [eval]
+-          major: (_|_){
+-            // [eval] outerErr.usingClose.t1.version.major: field not allowed:
+-            //     ./in.cue:19:8
+-            //     ./in.cue:34:23
+-            //     ./in.cue:35:22
+-            //     ./in.cue:37:7
+-            //     ./in.cue:38:16
+-          }
++    usingClose: (struct){
 +      #Inner: (#struct){
 +        foo: (#struct){
 +          minor: (int){ 2 }
@@ -291,97 +274,18 @@ diff old new
 +          major: (int){ 1 }
 +        }
 +      }
-+      t1: (_|_){
-+        // [eval]
-+        version: (_|_){
-+          // [eval]
-+          major: (_|_){
-+            // [eval] outerErr.issue3534.t1.version.major: field not allowed:
-+            //     ./in.cue:19:8
-+            //     ./in.cue:25:22
-+          }
++      t1: (#struct){
++        version: (#struct){
++          major: (int){ 1 }
            minor: (int){ 2 }
          }
        }
-@@ -62,43 +77,52 @@
-           // [eval]
-           major: (_|_){
-             // [eval] outerErr.usingClose.t1.version.major: field not allowed:
--            //     ./in.cue:19:8
--            //     ./in.cue:34:23
-+            //     ./in.cue:34:17
-             //     ./in.cue:35:22
--            //     ./in.cue:37:7
--            //     ./in.cue:38:16
--          }
--          minor: (int){ 2 }
--        }
--      }
--    }
--    extraNesting: (struct){
--      #Inner: (#struct){
--        foo: (#struct){
--          x: (#struct){
--            minor: (int){ 2 }
--          }
--        }
--      }
--      #Outer: (#struct){
--        version: (#struct){
--          x: (#struct){
--            major: (int){ 1 }
--          }
--        }
--      }
--      t1: (#struct){
--        version: (#struct){
--          x: (#struct){
--            major: (int){ 1 }
--            minor: (int){ 2 }
--          }
--        }
--      }
--    }
--  }
+@@ -97,8 +86,13 @@
+       }
+     }
+   }
 -  refFromPkg: (int){ 1 }
 -  refFromLet: (struct){
-+          }
-+          minor: (int){ 2 }
-+        }
-+      }
-+    }
-+    extraNesting: (_|_){
-+      // [eval]
-+      #Inner: (#struct){
-+        foo: (#struct){
-+          x: (#struct){
-+            minor: (int){ 2 }
-+          }
-+        }
-+      }
-+      #Outer: (#struct){
-+        version: (#struct){
-+          x: (#struct){
-+            major: (int){ 1 }
-+          }
-+        }
-+      }
-+      t1: (_|_){
-+        // [eval]
-+        version: (_|_){
-+          // [eval]
-+          x: (_|_){
-+            // [eval]
-+            major: (_|_){
-+              // [eval] outerErr.extraNesting.t1.version.x.major: field not allowed:
-+              //     ./in.cue:46:25
-+            }
-+            minor: (int){ 2 }
-+          }
-+        }
-+      }
-+    }
-+  }
 +  refFromPkg: (_|_){
 +    // [eval] #E.b: field not allowed:
 +    //     ./in.cue:57:14
@@ -392,7 +296,7 @@ diff old new
      let X#1 = (_|_){
        // [eval]
        #D: (#struct){
-@@ -106,15 +130,18 @@
+@@ -106,15 +100,18 @@
        }
        #E: (_|_){
          // [eval]

internal/core/adt/conjunct.go

@@ -78,7 +78,10 @@ func (n *nodeContext) scheduleConjunct(c Conjunct, id CloseInfo) {
 		if c.CloseInfo.FromDef {
 			t |= closeDef
 		}
-		if c.CloseInfo.FromEmbed {
+		// NOTE: the check for OpenInline is not strictly necessary, but it
+		// clarifies that using id.FromEmbed is not used when OpenInline is not
+		// used.
+		if c.CloseInfo.FromEmbed || (n.ctx.OpenInline && id.FromEmbed) {
 			t |= closeEmbed
 		}
 		if t != 0 || c.CloseInfo.GroupUnify {

internal/core/adt/context.go

@@ -1142,6 +1142,7 @@ func pos(x Node) token.Pos {
 func (c *OpContext) node(orig Node, x Expr, scalar bool, state combinedFlags) *Vertex {
 	if c.OpenInline {
 		if _, ok := x.(Resolver); !ok {
+			c.ci.FromEmbed = true
 			c.inLiteralSelectee++
 			defer func() { c.inLiteralSelectee-- }()
 		}

internal/cuedebug/debug.go

@@ -43,8 +43,21 @@ type Config struct {
 	//    x: (#D & {b: 2}).b // allow this
 	//
 	// This behavior was erroneously permitted in the v2 evaluator and was fixed
-	// in v3. This allows users that rely on this behavior to use v3.
+	// in v3. This allows users that rely on this behavior to use v3. This
+	// option also discards closedness of the resulting expression. As was
+	// reported in Issue #3534, this was another erroneous behavior in v2 that
+	// is otherwise fixed in v3.
+	//
 	// To aid the transition to v3, this is enabled by default for now.
+	//
+	// A possible solution for both incompatibilities would be the introduction
+	// of an openAll builtin to recursive open up a cue value. For the first
+	// issue, the example above could be rewritten as:
+	//
+	//     x: (openAll(#D) & {b: 2}).b
+	//
+	// For the second issue, to open up the entire result of an inline struct,
+	// such an expression could be written as `openAll(expr).out`.
 	OpenInline bool `envflag:"default:true"`
 }