shortnames: error if there's no alias and no search registries

When a short-name could not be resolved to an alias and if there's no
unqualified-search registry, throw an error.

Reported-in: github.com/containers/podman/issues/8573
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

pkg/shortnames/shortnames.go

@@ -225,9 +225,8 @@ func (c *PullCandidate) Record() error {
 // Note that tags and digests are stripped from the specified name before
 // looking up an alias. Stripped off tags and digests are later on appended to
 // all candidates.  If neither tag nor digest is specified, candidates are
-// normalized with the "latest" tag. PullCandidates in the returned value may
-// be empty if there is no matching alias and no unqualified-search registries
-// are configured.
+// normalized with the "latest" tag.  An error is returned if there is no
+// matching alias and no unqualified-search registries are configured.
 //
 // Note that callers *must* call `(PullCandidate).Record` after a returned
 // item has been pulled successfully; this callback will record a new
@@ -312,6 +311,10 @@ func Resolve(ctx *types.SystemContext, name string) (*Resolved, error) {
 	if err != nil {
 		return nil, err
 	}
+	// Error out if there's no matching alias and no search registries.
+	if len(unqualifiedSearchRegistries) == 0 {
+		return nil, errors.Errorf("short-name %q did not resolve to an alias and no unqualified-search registries are defined in %q", name, usrConfig)
+	}
 	resolved.originDescription = usrConfig
 
 	for _, reg := range unqualifiedSearchRegistries {
@@ -331,10 +334,8 @@ func Resolve(ctx *types.SystemContext, name string) (*Resolved, error) {
 		return resolved, nil
 	}
 
-	// If we have only one candidate, there's no ambiguity. In case of an
-	// empty candidate slices, callers can implement custom logic or raise
-	// an error.
-	if len(resolved.PullCandidates) <= 1 {
+	// If we have only one candidate, there's no ambiguity.
+	if len(resolved.PullCandidates) == 1 {
 		return resolved, nil
 	}
 

pkg/shortnames/shortnames_test.go

@@ -141,12 +141,11 @@ func TestResolve(t *testing.T) {
 		assert.False(t, resolved.PullCandidates[0].record)
 	}
 
-	// Non-existent should return an empty slice as no search registries
-	// are configured in the config.
+	// Non-existent should return an error as no search registries are
+	// configured in the config.
 	resolved, err := Resolve(sys, "dontexist")
-	require.NoError(t, err)
-	require.NotNil(t, resolved)
-	require.Len(t, resolved.PullCandidates, 0)
+	require.Error(t, err)
+	require.Nil(t, resolved)
 
 	// An empty name is not valid.
 	resolved, err = Resolve(sys, "")
@@ -354,23 +353,23 @@ func TestResolveWithVaryingShortNameModes(t *testing.T) {
 		{"testdata/one-reg.conf", types.ShortNameModePermissive, "repo/image", false, 1},
 		{"testdata/two-reg.conf", types.ShortNameModePermissive, "repo/image", false, 1},
 		// Permisive + no match -> search (no tty)
-		{"testdata/no-reg.conf", types.ShortNameModePermissive, "donotexist", false, 0},
+		{"testdata/no-reg.conf", types.ShortNameModePermissive, "donotexist", true, 0},
 		{"testdata/one-reg.conf", types.ShortNameModePermissive, "donotexist", false, 1},
 		{"testdata/two-reg.conf", types.ShortNameModePermissive, "donotexist", false, 2},
 		// Disabled + match -> return alias
 		{"testdata/no-reg.conf", types.ShortNameModeDisabled, "repo/image", false, 1},
 		{"testdata/one-reg.conf", types.ShortNameModeDisabled, "repo/image", false, 1},
 		{"testdata/two-reg.conf", types.ShortNameModeDisabled, "repo/image", false, 1},
 		// Disabled + no match -> search
-		{"testdata/no-reg.conf", types.ShortNameModeDisabled, "donotexist", false, 0},
+		{"testdata/no-reg.conf", types.ShortNameModeDisabled, "donotexist", true, 0},
 		{"testdata/one-reg.conf", types.ShortNameModeDisabled, "donotexist", false, 1},
 		{"testdata/two-reg.conf", types.ShortNameModeDisabled, "donotexist", false, 2},
 		// Enforcing + match -> return alias
 		{"testdata/no-reg.conf", types.ShortNameModeEnforcing, "repo/image", false, 1},
 		{"testdata/one-reg.conf", types.ShortNameModeEnforcing, "repo/image", false, 1},
 		{"testdata/two-reg.conf", types.ShortNameModeEnforcing, "repo/image", false, 1},
 		// Enforcing + no match -> error if search regs > 1 and no tty
-		{"testdata/no-reg.conf", types.ShortNameModeEnforcing, "donotexist", false, 0},
+		{"testdata/no-reg.conf", types.ShortNameModeEnforcing, "donotexist", true, 0},
 		{"testdata/one-reg.conf", types.ShortNameModeEnforcing, "donotexist", false, 1},
 		{"testdata/two-reg.conf", types.ShortNameModeEnforcing, "donotexist", true, 0},
 	}