mod/modregistry: return empty list for Versions with invalid name

This fixes the module logic so that when there's a request
for a module that has a name that isn't OCI-compatible,
it will not even make the request to the module,
instead returning a "not found" error.

Signed-off-by: Roger Peppe <[email protected]>
Change-Id: Ie144e72181c05fa2f8d74a48210eb49ca9157b44
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1199212
Unity-Result: CUE porcuepine <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

cmd/cue/cmd/testdata/script/modtidy_badpath.txtar

@@ -5,17 +5,12 @@
 # might not return a 404 error, but some other kind of error.
 # The OCI proxy is one such registry.
 
-# TODO fix this so it works OK.
-! exec cue mod tidy
-cmp stderr want-stderr
+exec cue mod tidy
 
-# TODO enable these assertions.
-# cmp cue.mod/module.cue want-module
-# exec cue export
-# cmp stdout want-stdout
+cmp cue.mod/module.cue want-module
+exec cue export
+cmp stdout want-stdout
 
--- want-stderr --
-failed to resolve "test.example/foo/BarBaz": module test.example/foo/BarBaz: invalid OCI request: name invalid: invalid repository name
 -- want-module --
 module: "cue.example@v0"
 language: {

internal/mod/modload/testdata/tidy/badimportpath.txtar

@@ -3,7 +3,7 @@
 -- tidy-check-error --
 module is not tidy: missing dependency providing package x.com/Foo--bar@v0
 -- want --
-error: failed to resolve "x.com/Foo--bar@v0": cannot obtain versions for module "x.com/Foo--bar@v0": module x.com/Foo--bar@v0: invalid OCI request: name invalid: invalid repository name
+error: failed to resolve "x.com/Foo--bar@v0": cannot find module providing package x.com/Foo--bar@v0
 -- cue.mod/module.cue --
 language: version: "v0.8.0"
 module: "main.org@v0"

mod/modregistry/client.go

@@ -31,6 +31,7 @@ import (
 	"strings"
 
 	"cuelabs.dev/go/oci/ociregistry"
+	"cuelabs.dev/go/oci/ociregistry/ociref"
 	"cuelang.org/go/internal/mod/semver"
 	digest "github.com/opencontainers/go-digest"
 	specs "github.com/opencontainers/image-spec/specs-go"
@@ -173,7 +174,7 @@ func (c *Client) GetModuleWithManifest(m module.Version, contents []byte, mediaT
 // sorted in semver order.
 // If m has a major version suffix, only versions with that major version will
 // be returned.
-func (c *Client) ModuleVersions(ctx context.Context, m string) ([]string, error) {
+func (c *Client) ModuleVersions(ctx context.Context, m string) (_req []string, _err0 error) {
 	mpath, major, hasMajor := module.SplitPathVersion(m)
 	if !hasMajor {
 		mpath = m
@@ -186,6 +187,12 @@ func (c *Client) ModuleVersions(ctx context.Context, m string) ([]string, error)
 		return nil, err
 	}
 	versions := []string{}
+	if !ociref.IsValidRepository(loc.Repository) {
+		// If it's not a valid repository, it can't be used in an OCI
+		// request, so return an empty slice rather than the
+		// "invalid OCI request" error that a registry can return.
+		return nil, nil
+	}
 	// Note: do not use c.repoName because that always expects
 	// a module path with a major version.
 	iter := loc.Registry.Tags(ctx, loc.Repository, "")