fix: do not allow empty items in deb.provides (#606)

Signed-off-by: Carlos A Becker <[email protected]>

Signed-off-by: Carlos A Becker <[email protected]>

deb/deb.go

@@ -788,7 +788,7 @@ Installed-Size: {{.InstalledSize}}
 {{- with .Info.Replaces}}
 Replaces: {{join .}}
 {{- end }}
-{{- with .Info.Provides}}
+{{- with nonEmpty .Info.Provides}}
 Provides: {{join .}}
 {{- end }}
 {{- with .Info.Depends}}
@@ -833,6 +833,17 @@ func writeControl(w io.Writer, data controlData) error {
 			ret := strings.ReplaceAll(strs, "\n", "\n ")
 			return strings.Trim(ret, " \n")
 		},
+		"nonEmpty": func(strs []string) []string {
+			var result []string
+			for _, s := range strs {
+				s := strings.TrimSpace(s)
+				if s == "" {
+					continue
+				}
+				result = append(result, s)
+			}
+			return result
+		},
 	})
 	return template.Must(tmpl.Parse(controlTemplate)).Execute(w, data)
 }

deb/deb_test.go

@@ -1397,3 +1397,19 @@ func TestGlob(t *testing.T) {
 		},
 	}), io.Discard))
 }
+
+func TestBadProvides(t *testing.T) {
+	var w bytes.Buffer
+	info := exampleInfo()
+	info.Provides = []string{"  "}
+	require.NoError(t, writeControl(&w, controlData{
+		Info: nfpm.WithDefaults(info),
+	}))
+	golden := "testdata/bad_provides.golden"
+	if *update {
+		require.NoError(t, os.WriteFile(golden, w.Bytes(), 0o600))
+	}
+	bts, err := os.ReadFile(golden) //nolint:gosec
+	require.NoError(t, err)
+	require.Equal(t, string(bts), w.String())
+}

deb/testdata/bad_provides.golden

@@ -0,0 +1,14 @@
+Package: foo
+Version: 1.0.0
+Section: default
+Priority: extra
+Architecture: amd64
+Maintainer: Carlos A Becker <[email protected]>
+Installed-Size: 0
+Replaces: svn
+Depends: bash
+Recommends: git
+Suggests: bash
+Conflicts: zsh
+Homepage: http://carlosbecker.com
+Description: Foo does things