fix: unmarshal additional disks (#613)

Issue #, if available:

*Description of changes:*

disks in the list format in lima override.yaml were not being
unmarshalled properly, causing a disk with the name "" to be mixed with
finch lima yaml, resulting in startup failure. This only occurs on inits
of a vm other than the very first init. init a vm the first time,
_output/lima/data/_config/override.yaml:

```yaml
additionalDisks:
    - name: finch
```

stop and remove the vm, then re-init:
```yaml
additionalDisks:
    - name: ""
    - name: finch
```

to fix, copy upstream logic from lima to use a custom unmarshaler for
the Disk type.

*Testing done:*

`make test-unit`

manual testing

- [x] I've reviewed the guidance in CONTRIBUTING.md


#### License Acceptance

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.

Signed-off-by: Gavin Inglis <[email protected]>

pkg/config/lima_config_applier.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"strings"
 
+	goyaml "github.com/goccy/go-yaml"
 	"github.com/lima-vm/lima/pkg/limayaml"
 	"github.com/spf13/afero"
 	"github.com/xorcare/pointer"
@@ -102,6 +103,12 @@ func (lca *limaConfigApplier) Apply(isInit bool) error {
 		return fmt.Errorf("failed to unmarshal the lima config file: %w", err)
 	}
 
+	// Unmarshall with custom unmarshaler for Disk:
+	// https://github.com/lima-vm/lima/blob/v0.17.2/pkg/limayaml/load.go#L16
+	if err := goyaml.UnmarshalWithOptions(b, &limaCfg, goyaml.DisallowDuplicateKey(), goyaml.CustomUnmarshaler[limayaml.Disk](unmarshalDisk)); err != nil {
+		return fmt.Errorf("failed to unmarshal the lima config file: %w", err)
+	}
+
 	limaCfg.CPUs = lca.cfg.CPUs
 	limaCfg.Memory = lca.cfg.Memory
 	limaCfg.Mounts = []limayaml.Mount{}
@@ -141,7 +148,7 @@ func (lca *limaConfigApplier) Apply(isInit bool) error {
 
 	toggleSnaphotters(&limaCfg, snapshotters)
 
-	if *lca.cfg.VMType != "wsl2" {
+	if *lca.cfg.VMType != "wsl2" && len(limaCfg.AdditionalDisks) == 0 {
 		limaCfg.AdditionalDisks = append(limaCfg.AdditionalDisks, limayaml.Disk{
 			Name: "finch",
 		})
@@ -244,3 +251,13 @@ func findWslDiskFormatScript(limaCfg *limayaml.LimaYAML) bool {
 
 	return hasWslDiskFormatScript
 }
+
+// https://github.com/lima-vm/lima/blob/v0.17.2/pkg/limayaml/load.go#L16
+func unmarshalDisk(dst *limayaml.Disk, b []byte) error {
+	var s string
+	if err := goyaml.Unmarshal(b, &s); err == nil {
+		*dst = limayaml.Disk{Name: s}
+		return nil
+	}
+	return goyaml.Unmarshal(b, dst)
+}