go-delve/delve · error

invalid Filter pattern: %v

Error message

invalid Filter pattern: %v

What it means

ListPackagesBuildInfo throws this when the optional Filter field is not a valid Go regular expression. The handler compiles in.Filter with regexp.Compile before filtering packages, and compilation failure is reported with the underlying regexp error.

Source

Thrown at service/rpc2/server.go:966

	Filter       string // if not empty, returns only packages matching the regexp.
}

// ListPackagesBuildInfoOut holds the return values of ListPackagesBuildInfo.
type ListPackagesBuildInfoOut struct {
	List []api.PackageBuildInfo
}

// ListPackagesBuildInfo returns the list of packages used by the program along with
// the directory where each package was compiled and optionally the list of
// files constituting the package.
// Note that the directory path is a best guess and may be wrong is a tool
// other than cmd/go is used to perform the build.
func (s *RPCServer) ListPackagesBuildInfo(in ListPackagesBuildInfoIn, out *ListPackagesBuildInfoOut) error {
	var pattern *regexp.Regexp
	if in.Filter != "" {
		p, err := regexp.Compile(in.Filter)
		if err != nil {
			return fmt.Errorf("invalid Filter pattern: %v", err)
		}
		pattern = p
	}
	pkgs := s.debugger.ListPackagesBuildInfo(in.IncludeFiles)
	out.List = make([]api.PackageBuildInfo, 0, len(pkgs))
	for _, pkg := range pkgs {
		if pattern != nil && !pattern.MatchString(pkg.ImportPath) {
			continue
		}
		var files []string

		if len(pkg.Files) > 0 {
			files = make([]string, 0, len(pkg.Files))
			for file := range pkg.Files {
				files = append(files, file)
			}
		}

View on GitHub (pinned to a23773e6c3)

Solutions

1. Validate the pattern with regexp.Compile before sending it over RPC and surface the error locally
2. Convert glob patterns to regexp syntax: '*' -> '.*', escape '.' as '\\.'
3. Escape user-supplied substrings with regexp.QuoteMeta when the intent is literal matching
4. Remember Go uses RE2: remove PCRE-only constructs like backreferences or lookaheads

Example fix

// before
_, err := client.ListPackagesBuildInfo(rpc2.ListPackagesBuildInfoIn{Filter: "pkg/(net|http"}) // unbalanced paren
// after
if _, cerr := regexp.Compile("pkg/(net|http)"); cerr != nil {
    return cerr // fail fast client-side
}
_, err := client.ListPackagesBuildInfo(rpc2.ListPackagesBuildInfoIn{Filter: "pkg/(net|http)"})

func validFilter(f string) error {
    if f == "" { return nil }
    _, err := regexp.Compile(f)
    return err
}
// call: if err := validFilter(in.Filter); err != nil { return err }

_, err := client.ListPackagesBuildInfo(rpc2.ListPackagesBuildInfoIn{Filter: pattern})
if err != nil && strings.Contains(err.Error(), "invalid Filter pattern") {
    return fmt.Errorf("bad --filter regexp: %w", err)
}

When it happens

Trigger: Calling RPCClient.ListPackagesBuildInfo with ListPackagesBuildInfoIn.Filter set to a syntactically invalid regexp, e.g. unbalanced parentheses '(' , a dangling '*' as the first character, or a bad escape like '\q'.

Common situations: Users typing glob-style filters ('pkg/*' instead of 'pkg/.*') into tooling that passes them straight through as regexps; programmatically-built filters where user input is interpolated unescaped; patterns copied from grep/sed with syntax Go's RE2 rejects (e.g. backreferences).

Related errors

• mismatched length in addrs and addrpid
• can not call function with nil ReturnInfoLoadConfig
• channel filter can not be negated
• count == 0 not allowed with a channel filter
• channel filter without eval scope

AI-assisted analysis of go-delve/delve@a23773e6c3 (2026-08-31). Data as JSON: /api/errors/c61a0580c6fdb6bf. Report an issue: GitHub.