Add binary body formatting to the logging feature

Binary request bodies (IO/Enumerable sources and binary-encoded strings)
and binary-encoded response bodies are now formatted instead of dumped
raw, preventing unreadable log output when transferring files.

Add `Request::Body#loggable?` and `Response::Body#loggable?` predicates
to detect inspectable body content, and a `binary_formatter` option on
the Logging feature with three modes:
* `:stats` (default) — logs "BINARY DATA (N bytes)"
* `:base64` — logs base64-encoded content with byte count
* `Proc` — custom formatting via a callable

Closes #784.

Author: sferik

CHANGELOG.md

@@ -27,6 +27,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   per RFC 3986. Supports chaining (`HTTP.base_uri("https://api.example.com/v1")
   .get("users")`), and integrates with `persistent` connections by deriving the
   host when omitted (#519, #512, #493)
+- `Request::Body#loggable?` and `Response::Body#loggable?` predicates, and a
+  `binary_formatter` option for the logging feature. Binary bodies
+  (IO/Enumerable request sources, binary-encoded request strings, and
+  binary-encoded responses) are now formatted instead of dumped raw,
+  preventing unreadable log output when transferring files like images or
+  audio. Available formatters: `:stats` (default, logs byte count),
+  `:base64` (logs base64-encoded content), or a custom `Proc`. Invalid
+  formatter values raise `ArgumentError` (#784)
 - `Feature#on_request` and `Feature#around_request` lifecycle hooks, called
   before/around each request attempt (including retries), for per-attempt side
   effects like instrumentation spans and circuit breakers (#826)

lib/http/features/logging.rb

@@ -9,6 +9,17 @@ module Features
     #
     #    HTTP.use(logging: {logger: Logger.new(STDOUT)}).get("https://example.com/")
     #
+    # Binary bodies (IO/Enumerable request sources and binary-encoded
+    # responses) are formatted using the +binary_formatter+ option instead
+    # of being dumped raw. Available formatters:
+    #
+    # - +:stats+ (default) — logs <tt>BINARY DATA (N bytes)</tt>
+    # - +:base64+ — logs <tt>BINARY DATA (N bytes)\n<base64></tt>
+    # - +Proc+ — calls the proc with the raw binary string
+    #
+    # @example Custom binary formatter
+    #    HTTP.use(logging: {logger: Logger.new(STDOUT), binary_formatter: :base64})
+    #
     class Logging < Feature
       HTTP::Options.register_feature(:logging, self)
 
@@ -39,12 +50,17 @@ class NullLogger
       # @example
       #   Logging.new(logger: Logger.new(STDOUT))
       #
+      # @example With binary formatter
+      #   Logging.new(logger: Logger.new(STDOUT), binary_formatter: :base64)
+      #
       # @param logger [#info, #debug] logger instance
+      # @param binary_formatter [:stats, :base64, #call] how to log binary bodies
       # @return [Logging]
       # @api public
-      def initialize(logger: NullLogger.new)
+      def initialize(logger: NullLogger.new, binary_formatter: :stats)
         super()
         @logger = logger
+        @binary_formatter = validate_binary_formatter!(binary_formatter)
       end
 
       # Logs and returns the request
@@ -57,7 +73,7 @@ def initialize(logger: NullLogger.new)
       # @api public
       def wrap_request(request)
         logger.info { "> #{request.verb.to_s.upcase} #{request.uri}" }
-        logger.debug { "#{stringify_headers(request.headers)}\n\n#{request.body.source}" }
+        log_request_details(request)
 
         request
       end
@@ -83,11 +99,43 @@ def wrap_response(response)
 
       private
 
+      # Validate and return the binary_formatter option
+      # @return [:stats, :base64, #call]
+      # @raise [ArgumentError] if the formatter is not a valid option
+      # @api private
+      def validate_binary_formatter!(formatter)
+        return formatter if formatter == :stats || formatter == :base64 || formatter.respond_to?(:call)
+
+        raise ArgumentError,
+              "binary_formatter must be :stats, :base64, or a callable " \
+              "(got #{formatter.inspect})"
+      end
+
+      # Log request headers and body (when loggable)
+      # @return [void]
+      # @api private
+      def log_request_details(request)
+        headers = stringify_headers(request.headers)
+        if request.body.loggable?
+          source = request.body.source
+          body = source.encoding == Encoding::BINARY ? format_binary(source) : source # steep:ignore
+          logger.debug { "#{headers}\n\n#{body}" }
+        else
+          logger.debug { headers }
+        end
+      end
+
       # Log response with body inline (for non-streaming string bodies)
       # @return [HTTP::Response]
       # @api private
       def log_response_body_inline(response)
-        logger.debug { "#{stringify_headers(response.headers)}\n\n#{response.body}" }
+        body    = response.body
+        headers = stringify_headers(response.headers)
+        if body.respond_to?(:encoding) && body.encoding == Encoding::BINARY # steep:ignore
+          logger.debug { "#{headers}\n\n#{format_binary(body)}" } # steep:ignore
+        else
+          logger.debug { "#{headers}\n\n#{body}" }
+        end
         response
       end
 
@@ -110,10 +158,25 @@ def logged_response_options(response)
       # @return [HTTP::Response::Body]
       # @api private
       def logged_body(body)
-        stream = BodyLogger.new(body.instance_variable_get(:@stream), logger)
+        formatter = body.loggable? ? nil : method(:format_binary) # steep:ignore
+        stream = BodyLogger.new(body.instance_variable_get(:@stream), logger, formatter: formatter) # steep:ignore
         Response::Body.new(stream, encoding: body.encoding)
       end
 
+      # Format binary data according to the configured binary_formatter
+      # @return [String]
+      # @api private
+      def format_binary(data)
+        case @binary_formatter
+        when :stats
+          format("BINARY DATA (%d bytes)", data.bytesize)
+        when :base64
+          format("BINARY DATA (%d bytes)\n%s", data.bytesize, [data].pack("m0"))
+        else
+          @binary_formatter.call(data) # steep:ignore
+        end
+      end
+
       # Convert headers to a string representation
       # @return [String]
       # @api private
@@ -139,12 +202,14 @@ class BodyLogger
         #
         # @param stream [#readpartial] the stream to wrap
         # @param logger [#debug] the logger instance
+        # @param formatter [#call, nil] optional formatter for each chunk
         # @return [BodyLogger]
         # @api public
-        def initialize(stream, logger)
+        def initialize(stream, logger, formatter: nil)
           @stream = stream
           @connection = stream.respond_to?(:connection) ? stream.connection : stream
           @logger = logger
+          @formatter = formatter
         end
 
         # Read a chunk from the underlying stream and log it
@@ -157,7 +222,7 @@ def initialize(stream, logger)
         # @api public
         def readpartial(*)
           chunk = @stream.readpartial(*)
-          @logger.debug { chunk }
+          @logger.debug { @formatter ? @formatter.call(chunk) : chunk } # steep:ignore
           chunk
         end
       end

lib/http/request/body.rb

@@ -37,6 +37,24 @@ def empty?
         @source.nil?
       end
 
+      # Whether the body content can be accessed for logging
+      #
+      # Returns true for String sources (the content can be inspected).
+      # Returns false for IO streams and Enumerables (which cannot be
+      # read without consuming them), and for nil bodies.
+      #
+      # The logging feature checks the string encoding separately to
+      # decide whether to log the content as text or format it as binary.
+      #
+      # @example
+      #   body.loggable? # => true
+      #
+      # @return [Boolean]
+      # @api public
+      def loggable?
+        @source.is_a?(String)
+      end
+
       # Returns size for the "Content-Length" header
       #
       # @example

lib/http/response/body.rb

@@ -115,6 +115,20 @@ def stream!
         @streaming = true
       end
 
+      # Whether the body content is suitable for logging
+      #
+      # Returns true when the body encoding is not binary. Binary responses
+      # (images, audio, compressed data) produce unreadable log output.
+      #
+      # @example
+      #   body.loggable? # => true
+      #
+      # @return [Boolean]
+      # @api public
+      def loggable?
+        @encoding != Encoding::BINARY
+      end
+
       # Easier to interpret string inspect
       #
       # @example

sig/http.rbs

@@ -395,21 +395,28 @@ module HTTP
 
       attr_reader logger: untyped
 
-      def initialize: (?logger: untyped) -> void
+      @binary_formatter: :stats | :base64 | ^(String) -> String
+
+      def initialize: (?logger: untyped, ?binary_formatter: :stats | :base64 | ^(String) -> String) -> void
       def wrap_request: (Request request) -> Request
       def wrap_response: (Response response) -> Response
 
       private
 
+      def validate_binary_formatter!: (:stats | :base64 | ^(String) -> String formatter) -> (:stats | :base64 | ^(String) -> String)
+      def log_request_details: (Request request) -> void
       def log_response_body_inline: (Response response) -> Response
       def logged_response_options: (Response response) -> Hash[Symbol, untyped]
       def logged_body: (Response::Body body) -> Response::Body
+      def format_binary: (String data) -> String
       def stringify_headers: (Headers headers) -> String
 
       class BodyLogger
         attr_reader connection: untyped
 
-        def initialize: (untyped stream, untyped logger) -> void
+        @formatter: (^(String) -> String)?
+
+        def initialize: (untyped stream, untyped logger, ?formatter: (^(String) -> String)?) -> void
         def readpartial: (?Integer size, ?String? outbuf) -> String
       end
     end
@@ -741,6 +748,7 @@ module HTTP
 
       def initialize: (untyped source) -> void
       def empty?: () -> bool
+      def loggable?: () -> bool
       def size: () -> Integer
       def each: () { (String) -> void } -> self
              | () -> Enumerator[String, self]
@@ -881,6 +889,7 @@ module HTTP
       def to_s: () -> untyped
       alias to_str to_s
       def stream!: () -> untyped
+      def loggable?: () -> bool
       def inspect: () -> String
 
       private