cmd/cue/cmd: add more package pattern wildcard test cases

In particular, to test all the scenarios that we explicitly do not wish
to support right now, or whose potential behavior isn't obvious at all.

For #3155.

Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: Ic866bb078ca0f36dc2615606fc65b790a0c5c9a0

cmd/cue/cmd/testdata/script/pkg_patterns.txtar

@@ -0,0 +1,108 @@
+# Test the various kinds of wildcard patterns that we do not support.
+
+# Patterns on modules other than the current module are not supported,
+# even though one valid package could be matched.
+! exec cue eval example.com/foo/...
+cmp stderr external.stderr
+exec cue eval example.com/foo
+stdout -count=1 '^self: "example.com/foo"$'
+
+# The "all", "cmd", and "std" patterns were inherited from Go,
+# but they do nothing useful right now.
+# TODO: decide whether to support or reject these.
+! exec cue eval all
+cmp stderr all.stderr
+! exec cue eval cmd
+cmp stderr cmd.stderr
+! exec cue eval std
+cmp stderr std.stderr
+
+# A lone wildcard, perhaps equivalent to "all", is not supported for now.
+# TODO: much like "all", decide whether to support or reject this.
+! exec cue eval ...
+cmp stderr dots.stderr
+
+# Patterns with a leading wildcard are not supported either,
+# as they could match any module ever published,
+# even though one valid package could be matched.
+! exec cue eval .../leaf
+cmp stderr dots-prefix.stderr
+exec cue eval ./alpha1/leaf
+stdout -count=1 '^self: "mod.com/alpha1/leaf"$'
+
+# A wildcard in the middle of a pattern, with the current module as a prefix
+# either as "dot" or as the full path.
+# TODO: Why does this succeed? What does the output mean? This seems broken.
+exec cue eval ./.../leaf
+cmp stderr dot-dots-middle.stderr
+! exec cue eval mod.com/.../leaf
+cmp stderr current-dots-middle.stderr
+
+# A wildcard in the middle of a pattern, with a dependency module as a prefix.
+! exec cue eval example.com/foo/.../bar
+cmp stderr external-dots-middle.stderr
+
+# Matching many external modules, which could mean registry requests.
+! exec cue eval example.com/...
+cmp stderr external-dots-multimod.stderr
+
+-- external.stderr --
+cue: "example.com/foo/..." matched no packages
+
+-- all.stderr --
+cue: "all" matched no packages
+
+-- cmd.stderr --
+cue: "cmd" matched no packages
+
+-- std.stderr --
+cue: "std" matched no packages
+
+-- dots.stderr --
+cue: "..." matched no packages
+
+-- dots-prefix.stderr --
+cue: ".../leaf" matched no packages
+
+-- dot-dots-middle.stderr --
+// mod.com@v0:root
+-- current-dots-middle.stderr --
+cue: "mod.com/.../leaf" matched no packages
+
+-- external-dots-middle.stderr --
+cue: "example.com/foo/.../bar" matched no packages
+
+-- external-dots-multimod.stderr --
+cue: "example.com/..." matched no packages
+
+-- cue.mod/module.cue --
+module: "mod.com"
+
+language: version: "v0.9.0"
+
+deps: "example.com/foo": v: "v0.0.1"
+-- root.cue --
+package root
+
+import "example.com/foo"
+
+foo.bar
+-- alpha1/leaf/leaf.cue --
+package leaf
+self: "mod.com/alpha1/leaf"
+-- beta1/leaf/leaf.cue --
+package leaf
+self: "mod.com/beta1/leaf"
+-- beta1/beta2/leaf/leaf.cue --
+package leaf
+self: "mod.com/beta1/beta2/leaf"
+-- _registry/example.com_foo_v0.0.1/cue.mod/module.cue --
+module: "example.com/foo@v0"
+language: version: "v0.8.0"
+
+-- _registry/example.com_foo_v0.0.1/foo.cue --
+package foo
+self: "example.com/foo"
+-- _registry/example.com_foo_v0.0.1/bar/bar.cue --
+package bar
+self: "example.com/foo/bar"