cmd/cue,cue/load: add tests for underscore packages

This change adds some tests that cover CUE's behavior
with respect to underscore package identifiers.
See issue #3167 for some previous discussion
on this area.

For #3167
For #3244

Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: Ib99400373e49065be6cbe50642c771a19df571d5
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1196719
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>

cmd/cue/cmd/testdata/script/load_pkg.txtar

@@ -36,8 +36,6 @@ cd ..
 -- data.cue --
 foo:3
 -- t.cue --
-package _
-
 foo: int
 bar: 3
 -- kube.cue --

cmd/cue/cmd/testdata/script/load_underscore.txtar

@@ -0,0 +1,34 @@
+# Test whether an import with a _ qualifer is allowed or not.
+
+# TODO(rog): this should fail; see https://cuelang.org/issue/3167
+exec cue export ./foo
+cmp stdout want-stdout
+
+# Check that it also fails with an explicit _ qualifier
+# specified on the command line.
+# TODO(rog): this should fail similarly.
+exec cue export other.example/m:_
+cmp stdout want-stdout
+-- want-stdout --
+{
+    "x": 20
+}
+-- cue.mod/gen/other.example/m/m.cue --
+package _
+x: 20
+
+-- cue.mod/module.cue --
+module: "test.example/foo"
+language: version: "v0.9.0"
+
+-- foo/foo.cue --
+// Note: the package name does not match the directory name,
+// which means that this is only resolvable with an explicit
+// qualifier when used as an import path, but is allowed
+// on the cue command line because there's only one
+// package in the directory.
+package bar
+
+import m "other.example/m:_"
+
+x: m.x

cmd/cue/cmd/testdata/script/load_with_unnamed_pkg.txtar

@@ -0,0 +1,35 @@
+# Test that the command-line "allow single package
+# even when the package name does not match the import
+# path" logic works correctly in the presence of an
+# non-package CUE file, which can never be part
+# of a package.
+# See https://cuelang.org/issue/3244
+
+cd foo
+# TODO(rog): this should succeed
+! exec cue export
+cmp stderr $WORK/want-stderr
+-- want-stderr --
+test.example/foo@v0: import failed: no dependency found for package "other.example/m":
+    ./foo.cue:8:8
+-- cue.mod/gen/other.example/m/m.cue --
+package m
+x: 20
+
+-- cue.mod/module.cue --
+module: "test.example"
+language: version: "v0.9.0"
+
+-- foo/foo.cue --
+// Note: the package name does not match the directory name,
+// which means that this is only resolvable with an explicit
+// qualifier when used as an import path, but is allowed
+// on the cue command line because there's only one
+// package in the directory.
+package bar
+
+import "other.example/m"
+
+x: m.x
+-- foo/unnamed.cue --
+import ()

cue/load/loader_test.go

@@ -470,7 +470,38 @@ display:.
 files:
     $CWD/testdata/testmod/multi3/other.cue
 imports:
-    mod.test/test/sub: $CWD/testdata/testmod/sub/sub.cue`}}
+    mod.test/test/sub: $CWD/testdata/testmod/sub/sub.cue`}, {
+		// Test that we can explicitly ask for non-package
+		// CUE files by setting Config.Package to "_".
+		name: "ExplicitPackageWithUnqualifiedImportPath#4",
+		cfg: &Config{
+			Dir:     filepath.Join(testdataDir, "multi4"),
+			Package: "_",
+		},
+		args: []string{"."},
+		want: `path:   mod.test/test/multi4@v0:_
+module: mod.test/test@v0
+root:   $CWD/testdata/testmod
+dir:    $CWD/testdata/testmod/multi4
+display:.
+files:
+    $CWD/testdata/testmod/anon.cue
+    $CWD/testdata/testmod/multi4/nopackage1.cue
+    $CWD/testdata/testmod/multi4/nopackage2.cue`}, {
+		// Test what happens when there's a single CUE file
+		// with an explicit `package _` directive.
+		name: "ExplicitPackageWithUnqualifiedImportPath#5",
+		cfg: &Config{
+			Dir:     filepath.Join(testdataDir, "multi5"),
+			Package: "_",
+		},
+		args: []string{"."},
+		want: `err:    found packages "main" (file.cue) and "_" (nopackage.cue) in "multi5"
+path:   ""
+module: mod.test/test@v0
+root:   $CWD/testdata/testmod
+dir:    ""
+display:""`}}
 	tdtest.Run(t, testCases, func(t *tdtest.T, tc *loadTest) {
 		pkgs := Instances(tc.args, tc.cfg)
 

cue/load/testdata/testmod/multi/nopackage1.cue

@@ -0,0 +1,2 @@
+x: 1
+

cue/load/testdata/testmod/multi4/file.cue

@@ -0,0 +1,5 @@
+// Test data - not compiled.
+
+package main
+
+{}

cue/load/testdata/testmod/multi4/file_appengine.cue

@@ -0,0 +1,5 @@
+// Test data - not compiled.
+
+package test_package
+
+{}

cue/load/testdata/testmod/multi4/nopackage1.cue

@@ -0,0 +1,2 @@
+x: 1
+

cue/load/testdata/testmod/multi4/nopackage2.cue

@@ -0,0 +1,7 @@
+// The underscore package should be treated the same as an omitted package
+// clause.
+
+package _
+
+x: 1
+

cue/load/testdata/testmod/multi5/file.cue

@@ -0,0 +1,5 @@
+// Test data - not compiled.
+
+package main
+
+{}

cue/load/testdata/testmod/multi5/multi/file.cue

@@ -0,0 +1,5 @@
+// Test data - not compiled.
+
+package main
+
+{}

cue/load/testdata/testmod/multi5/multi/file_appengine.cue

@@ -0,0 +1,5 @@
+// Test data - not compiled.
+
+package test_package
+
+{}

cue/load/testdata/testmod/multi5/multi/nopackage1.cue

@@ -0,0 +1,2 @@
+x: 1
+

cue/load/testdata/testmod/multi5/multi/nopackage2.cue

@@ -0,0 +1,7 @@
+// The underscore package should be treated the same as an omitted package
+// clause.
+
+package _
+
+x: 1
+

cue/load/testdata/testmod/multi5/nopackage.cue

@@ -0,0 +1,7 @@
+// The underscore package should be treated the same as an omitted package
+// clause.
+
+package _
+
+x: 1
+