Limit number of candidates for executables

This change ensures that the first match of an executable in the path
is retured instead of a list of candidates. This prevents a CDI spec,
for example, from containing multiple entries for a single executable
(e.g. nvidia-smi).

Signed-off-by: Evan Lezar <elezar@nvidia.com>

internal/lookup/executable.go

@@ -41,6 +41,7 @@ func newExecutableLocator(logger *log.Logger, root string, paths ...string) *exe
 		WithRoot(root),
 		WithSearchPaths(paths...),
 		WithFilter(assertExecutable),
+		WithCount(1),
 	)
 
 	l := executable{

internal/lookup/file.go

@@ -31,6 +31,7 @@ type file struct {
 	root     string
 	prefixes []string
 	filter   func(string) error
+	count    int
 }
 
 // Option defines a function for passing options to the NewFileLocator() call
@@ -65,6 +66,13 @@ func WithFilter(assert func(string) error) Option {
 	}
 }
 
+// WithCount sets the maximum number of candidates to discover
+func WithCount(count int) Option {
+	return func(f *file) {
+		f.count = count
+	}
+}
+
 // NewFileLocator creates a Locator that can be used to find files with the specified options.
 func NewFileLocator(opts ...Option) Locator {
 	return newFileLocator(opts...)
@@ -126,6 +134,8 @@ var _ Locator = (*file)(nil)
 // All prefixes are searched and any matching candidates are returned. If no matches are found, an error is returned.
 func (p file) Locate(pattern string) ([]string, error) {
 	var filenames []string
+
+visit:
 	for _, prefix := range p.prefixes {
 		pathPattern := filepath.Join(prefix, pattern)
 		candidates, err := filepath.Glob(pathPattern)
@@ -141,8 +151,13 @@ func (p file) Locate(pattern string) ([]string, error) {
 				continue
 			}
 			filenames = append(filenames, candidate)
+			if p.count > 0 && len(filenames) == p.count {
+				p.logger.Debugf("Found %d candidates; ignoring further candidates", len(filenames))
+				break visit
 			}
 		}
+	}
+
 	if len(filenames) == 0 {
 		return nil, fmt.Errorf("pattern %v not found", pattern)
 	}