jmsperu opened a new pull request, #152:
URL: https://github.com/apache/cloudstack-go/pull/152
Fixes #103.
### Problem
The generated `Get<Entity>ID` / `Get<Entity>ByID` helpers index the result
slice at `[0]` as soon as `Count == 1`, without checking that the slice is
actually non-empty:
```go
if l.Count == 1 {
return l.VirtualMachinesMetrics[0].Id, l.Count, nil
}
```
When the backend reports `count >= 1` but returns an empty list — a
count/slice mismatch that occurs e.g. on the metrics APIs — this panics:
```
panic: runtime error: index out of range [0] with length 0
```
This is the panic reported in #103 (it surfaced via CAPC calling
`GetVirtualMachinesMetricID`). As @rajeshvenkata suggested in the issue, the
helper should check the slice before accessing it.
### Fix
The helpers are generated, so the root-cause fix is in the generator
template (`generate/generate.go`, both the `Get<Entity>ID` and
`Get<Entity>ByID` emitters). A length guard is emitted before the `[0]` access,
returning the same `No match found` error already used for the `count == 0`
case. The guard is then applied to the generated helpers — **additive only**
(212 guards across 64 files; no other lines change), so the diff stays
reviewable and a future regeneration reproduces it.
### Test
Adds `test/GetMetricIDRegression_test.go`, a self-contained regression test
that serves `{"count":1,"virtualmachine":[]}` and asserts
`GetVirtualMachinesMetricID` returns an error rather than panicking. It
**panics on the unpatched code** (reproducing #103) and **passes with the
guard**.
### Verification
- `go build ./...` — clean
- `go test ./test/ -run
TestGetVirtualMachinesMetricIDEmptyListWithNonZeroCount` — passes (and fails
with the exact `index out of range [0]` panic when the guard is reverted)
### Note
The count/empty-list mismatch this guards against is the same family as the
metrics JSON-tag issues (#135/#136, PR #137): when a response key does not
match the struct tag, `count` parses but the slice is `nil`. This guard makes
the helpers robust to that regardless of root cause.
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