[easy][bugs] Fix 2 package input bugs (#991)

## Summary

Fixes 2 bugs:

* Avoid triple slashes that can make comparing urls break when adding
flakes (this was affecting correct removal of profile packages and also
detecting that they were already installed)
* Fix package validation for non-versioned packages (They should use nix
search instead of new search service)

## How was it tested?

* `devbox add sqlite3`  showed error and was not added to devbox.json
* In examples/flake/php added and removed packages and confirmed profile
remained in sync.

Author: mikeland73

internal/nix/input.go

@@ -27,8 +27,9 @@ type Input struct {
 func InputFromString(s string, l lock.Locker) *Input {
 	u, _ := url.Parse(s)
 	if u.Path == "" && u.Opaque != "" && u.Scheme == "path" {
-		u.Path = filepath.Join(l.ProjectDir(), u.Opaque)
-		u.Opaque = ""
+		// This normalizes url paths to be absolute. It also ensures all
+		// path urls have a single slash (instead of possibly 3 slashes)
+		u, _ = url.Parse("path:" + filepath.Join(l.ProjectDir(), u.Opaque))
 	}
 	return &Input{*u, l}
 }
@@ -136,19 +137,18 @@ func (i *Input) PackageAttributePath() (string, error) {
 				strings.Join(lo.Keys(infos), ", ")
 		}
 		return "", usererr.New(
-			"Flake \"%s\" is ambiguous. %s",
+			"Package \"%s\" is ambiguous. %s",
 			i.String(),
 			outputs,
 		)
 	}
 
-	return "", usererr.New("Flake \"%s\" was not found", i.String())
+	return "", usererr.New("Package \"%s\" was not found", i.String())
 }
 
 func (i *Input) urlWithoutFragment() string {
 	u := i.URL // get copy
 	u.Fragment = ""
-	// This will produce urls with extra slashes after the scheme, but that's ok
 	return u.String()
 }
 
@@ -161,7 +161,7 @@ func (i *Input) hash() string {
 }
 
 func (i *Input) validateExists() (bool, error) {
-	if i.IsDevboxPackage() {
+	if i.isVersioned() {
 		version := i.version()
 		if version == "" && i.isVersioned() {
 			return false, usererr.New("No version specified for %q.", i.Path)

internal/nix/input_test.go

@@ -29,16 +29,16 @@ func TestInput(t *testing.T) {
 		{
 			pkg:                "path:path/to/my-flake#my-package",
 			isFlake:            true,
-			name:               "my-flake-c7758d",
-			urlWithoutFragment: "path://" + filepath.Join(projectDir, "path/to/my-flake"),
-			urlForInput:        "path://" + filepath.Join(projectDir, "path/to/my-flake"),
+			name:               "my-flake-eaedce",
+			urlWithoutFragment: "path:" + filepath.Join(projectDir, "path/to/my-flake"),
+			urlForInput:        "path:" + filepath.Join(projectDir, "path/to/my-flake"),
 		},
 		{
 			pkg:                "path:.#my-package",
 			isFlake:            true,
-			name:               "my-project-744eaa",
-			urlWithoutFragment: "path://" + projectDir,
-			urlForInput:        "path://" + projectDir,
+			name:               "my-project-bbeb05",
+			urlWithoutFragment: "path:" + projectDir,
+			urlForInput:        "path:" + projectDir,
 		},
 		{
 			pkg:                "path:/tmp/my-project/path/to/my-flake#my-package",