fix: handle StringFromCharset against empty charset and add Unit test for rand package

[richochetclementine1315]

What

Fixes a panic in StringFromCharset(n, charset) — it panicked with crypto/rand: argument to Int is <= 0 when called with an empty charset and n > 0, instead of returning an error the way its other failure paths already do. Also adds the first unit test coverage for pkg/util/rand, which previously had none.

Why

Closes #493

Changes

• pkg/util/rand/rand.go: guard against an empty charset before calling crypto/rand.Int, returning a descriptive error instead of panicking.
• pkg/util/rand/rand_test.go: table-driven tests for String and StringFromCharset, covering:
  • output length matches requested length across zero/single/short/long inputs
  • output characters all belong to the supplied/default charset
  • two calls with identical parameters produce different output
  • single-character charset behavior
  • empty-charset behavior — the case that previously panicked and now correctly returns an error

Testing

• go test ./pkg/util/rand/... -v — all cases pass, including the previously-panicking empty-charset case.
• go test ./... — full suite passes.

Notes

No behavior change for any existing valid input — String() and existing callers of StringFromCharset() with a non-empty charset are unaffected. This only changes behavior for the previously-panicking empty-charset edge case, and adds coverage that didn't exist before.

[github-actions]

👋 @richochetclementine1315

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[Copilot]

Pull request overview

This PR fixes a panic in pkg/util/rand.StringFromCharset when called with an empty charset (by returning an error instead) and introduces the first unit tests for the pkg/util/rand package to cover key behaviors and edge cases.

Changes:

• Add an input guard to prevent crypto/rand.Int from panicking on empty charset when n > 0.
• Add table-driven tests for String / StringFromCharset, including the previously panicking empty-charset case.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
pkg/util/rand/rand.go	Adds empty-charset validation to prevent a panic and return a descriptive error.
pkg/util/rand/rand_test.go	Introduces initial unit test coverage for string generation and charset constraints.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

pkg/util/rand/rand_test.go:108

• StringFromCharset now has an explicit negative-length error path. Add unit tests for negative n (both StringFromCharset and String) so this behavior doesn’t regress back to panicking on make([]byte, n).

func TestStringFromCharsetEmptyCharset(t *testing.T) {
	t.Parallel()

	got, err := StringFromCharset(5, "")
	if err == nil {

[richochetclementine1315]

@Vaishnav88sk @lbroudoux @yada @Harsh4902 requesting to review and suggest changes if needed

[Vaishnav88sk]

LGTM @Harsh4902

[Caesarsage]

+1 — verified the guards cover both reported panics: the empty-charset case, and via the n<0 check the String(-1) case from #359 (String delegates to StringFromCharset). One nit: gofmt the new guard lines (if n<0{). When this merges, #359, #493 and #360 can all close against it — #360 predates this with the same idea, so a credit mention there would be a kind touch.

[Harsh4902]

GTG

[github-actions]

🎉 @richochetclementine1315

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[richochetclementine1315]

Thankyou Everyone!!...Looking forward to making more meaningful and quality contributions at MicrocksCLI...