class TracePoint

A class that provides the functionality of Kernel#set_trace_func in a well-structured Object-Oriented API.

Example

Use TracePoint to gather information specifically for exceptions:

trace = TracePoint.new(:raise) do |tp|
  p [tp.lineno, tp.event, tp.raised_exception]
end
#=> #<TracePoint:disabled>

trace.enable  #=> false

0 / 0
#=> [5, :raise, #<ZeroDivisionError: divided by 0>]

Events

If you don’t specify the types of events you want to listen for, TracePoint will include all available events.

Note: Do not depend on the current event set, as this list is subject to change. Instead, it is recommended to specify the types of events you want to use.

To filter what is traced, you can pass any number of the following as events:

:line : Execute an expression or statement on a new line.

:class : Start a class or module definition.

:end : Finish a class or module definition.

:call : Call a Ruby method.

:return : Return from a Ruby method.

:c_call : Call a C-language routine.

:c_return : Return from a C-language routine.

:raise : Raise an exception.

:rescue : Rescue an exception.

:b_call : Event hook at block entry.

:b_return : Event hook at block ending.

:a_call : Event hook at all calls (call, b_call, and c_call).

:a_return : Event hook at all returns (return, b_return, and c_return).

:thread_begin : Event hook at thread beginning.

:thread_end : Event hook at thread ending.

:fiber_switch : Event hook at fiber switch.

:script_compiled : New Ruby code compiled (with eval, load, or require).

Public Class Methods

allow_reentry

[T] () { (nil) → T } → T

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 191
def self.allow_reentry: [T] () { (nil) -> T } -> T

Generally, while a TracePoint callback is running, other registered callbacks are not called to avoid confusion from reentrance. This method allows reentrance within a given block. Use this method carefully to avoid infinite callback invocation.

If called when reentrance is already allowed, it raises a RuntimeError.

Example:

# Without reentry
# ---------------

line_handler = TracePoint.new(:line) do |tp|
  next if tp.path != __FILE__ # Only works in this file
  puts "Line handler"
  binding.eval("class C; end")
end.enable

class_handler = TracePoint.new(:class) do |tp|
  puts "Class handler"
end.enable

class B
end

# This script will print "Class handler" only once: when inside the :line
# handler, all other handlers are ignored.

# With reentry
# ------------

line_handler = TracePoint.new(:line) do |tp|
  next if tp.path != __FILE__ # Only works in this file
  next if (__LINE__..__LINE__+3).cover?(tp.lineno) # Prevent infinite calls
  puts "Line handler"
  TracePoint.allow_reentry { binding.eval("class C; end") }
end.enable

class_handler = TracePoint.new(:class) do |tp|
  puts "Class handler"
end.enable

class B
end

# This will print "Class handler" twice: inside the allow_reentry block in the :line
# handler, other handlers are enabled.

Note that the example shows the principal effect of the method, but its practical usage is for debugging libraries that sometimes require other libraries’ hooks to not be affected by the debugger being inside trace point handling. Precautions should be taken against infinite recursion in this case (note that we needed to filter out calls by itself from the :line handler, otherwise it would call itself infinitely).

new

(*_ToSym events) { (instance tp) → void } → instance

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 130
def self.new: (*_ToSym events) { (instance tp) -> void } -> instance

Returns a new TracePoint object, not enabled by default.

To activate the TracePoint object, use TracePoint#enable:

trace = TracePoint.new(:call) do |tp|
  p [tp.lineno, tp.defined_class, tp.method_id, tp.event]
end
#=> #<TracePoint:disabled>

trace.enable  #=> false

puts "Hello, TracePoint!"
# ...
# [48, IRB::Notifier::AbstractNotifier, :printf, :call]
# ...

To deactivate the trace, use TracePoint#disable.

trace.disable

See Events at TracePoint for possible events and more information.

A block must be given; otherwise, an ArgumentError is raised.

If the trace method isn’t supported for the given event(s) filter, a RuntimeError is raised.

TracePoint.trace(:line) do |tp|
  p tp.raised_exception
end
#=> RuntimeError: 'raised_exception' not supported by this event

If the trace method is called outside a block, a RuntimeError is raised.

TracePoint.trace(:line) do |tp|
  $tp = tp
end
$tp.lineno #=> access from outside (RuntimeError)

Access from other ractors, threads or fibers is forbidden. TracePoints are active per-ractor so if you enable a TracePoint in one ractor, other ractors will not be affected.

stat

() → untyped

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 204
def self.stat: () -> untyped

Returns internal information of TracePoint.

The contents of the returned value are implementation-specific and may change in the future.

This method is only for debugging TracePoint itself.

trace

(*_ToSym events) { (instance tp) → void } → instance

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 218
def self.trace: (*_ToSym events) { (instance tp) -> void } -> instance

A convenience method for TracePoint.new that activates the trace automatically.

trace = TracePoint.trace(:call) { |tp| [tp.lineno, tp.event] }
#=> #<TracePoint:enabled>

trace.enabled?  #=> true

Public Instance Methods

binding

() → Binding?

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 229
def binding: () -> Binding?

Returns the generated binding object from the event.

Note that for :c_call and :c_return events, the method returns nil, since C methods themselves do not have bindings.

callee_id

() → Symbol?

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 237
def callee_id: () -> Symbol?

Returns the called name of the method being called.

defined_class

() → (Class | Module)?

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 277
def defined_class: () -> (Class | Module)?

Returns the class or module of the method being called.

class C; def foo; end; end
trace = TracePoint.new(:call) do |tp|
  p tp.defined_class #=> C
end.enable do
  C.new.foo
end

If the method is defined by a module, then that module is returned.

module M; def foo; end; end
class C; include M; end
trace = TracePoint.new(:call) do |tp|
  p tp.defined_class #=> M
end.enable do
  C.new.foo
end

Note: defined_class returns the singleton class.

The 6th block parameter of Kernel#set_trace_func passes the original class attached by the singleton class.

This is a difference between Kernel#set_trace_func and TracePoint.

class C; def self.foo; end; end
trace = TracePoint.new(:call) do |tp|
  p tp.defined_class #=> #<Class:C>
end.enable do
  C.foo
end

disable

() → bool
[T] () { () → T } → T

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 311
def disable: () -> bool
             | [T] () { () -> T } -> T

Deactivates the trace.

Returns true if the trace was enabled. Returns false if the trace was disabled.

trace.enabled?  #=> true
trace.disable   #=> true (previous status)
trace.enabled?  #=> false
trace.disable   #=> false

If a block is given, the trace will only be disabled within the scope of the block.

trace.enabled?  #=> true

trace.disable do
  trace.enabled?
  # Only disabled for this block
end

trace.enabled?  #=> true

Note: You cannot access event hooks within the block.

trace.disable { p tp.lineno }
#=> RuntimeError: access from outside

enable

(?target: Method | UnboundMethod | RubyVM::InstructionSequence | Proc | nil, ?target_line: int?, ?target_thread: Thread | :default | nil) → bool
[T] (?target: Method | UnboundMethod | RubyVM::InstructionSequence | Proc | nil, ?target_line: int?, ?target_thread: Thread | :default | nil) { () → T } → T

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 370
def enable: (?target: Method | UnboundMethod | RubyVM::InstructionSequence | Proc | nil, ?target_line: int?, ?target_thread: Thread | :default | nil) -> bool
            | [T] (?target: Method | UnboundMethod | RubyVM::InstructionSequence | Proc | nil, ?target_line: int?, ?target_thread: Thread | :default | nil) { () -> T } -> T

Activates the trace.

Returns true if the trace was enabled. Returns false if the trace was disabled.

trace.enabled?  #=> false
trace.enable    #=> false (previous state)
                #   trace is enabled
trace.enabled?  #=> true
trace.enable    #=> true (previous state)
                #   trace is still enabled

If a block is given, the trace will only be enabled during the block execution. If target and target_line are both nil, then target_thread will default to the current thread if a block is given.

trace.enabled?  #=> false

trace.enable do
  trace.enabled?
  # Only enabled for this block and thread
end

trace.enabled?  #=> false

The target, target_line, and target_thread parameters are used to limit tracing to specified code objects. target should be a code object for which RubyVM::InstructionSequence.of will return an instruction sequence.

t = TracePoint.new(:line) { |tp| p tp }

def m1
  p 1
end

def m2
  p 2
end

t.enable(target: method(:m1))

m1
# Prints #<TracePoint:line test.rb:4 in `m1'>
m2
# Prints nothing

Note: You cannot access event hooks within the enable block.

trace.enable { p tp.lineno }
#=> RuntimeError: access from outside

enabled?

() → bool

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 379
def enabled?: () -> bool

Returns the current status of the trace.

eval_script

() → String?

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 470
def eval_script: () -> String?

Returns the compiled source code (String) from eval methods on the :script_compiled event. If loaded from a file, it returns nil.

event

() → ::Symbol

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 389
def event: () -> ::Symbol

Returns the type of event.

See Events at TracePoint for more information.

inspect

() → String

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 397
def inspect: () -> String

Returns a string containing a human-readable TracePoint status.

instruction_sequence

() → RubyVM::InstructionSequence

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 482
def instruction_sequence: () -> RubyVM::InstructionSequence

Returns the compiled instruction sequence represented by a RubyVM::InstructionSequence instance on the :script_compiled event.

Note that this method is CRuby-specific.

lineno

() → Integer

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 405
def lineno: () -> Integer

Returns the line number of the event.

method_id

() → Symbol?

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 413
def method_id: () -> Symbol?

Returns the name at the definition of the method being called.

parameters

() → Method::param_types?

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 430
def parameters: () -> Method::param_types?

Returns the parameter definitions of the method or block that the current hook belongs to. The format is the same as for Method#parameters.

path

() → String

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 421
def path: () -> String

Returns the path of the file being executed.

raised_exception

() → Exception

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 439
def raised_exception: () -> Exception

Returns the exception raised on the :raise event or rescued on the :rescue event.

return_value

() → untyped

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 448
def return_value: () -> untyped

Returns the return value from :return, :c_return, and :b_return events.

self

() → untyped

Source

# File vendor/bundle/ruby/4.0.0/gems/rbs-4.0.3/core/trace_point.rbs, line 461
def self: () -> untyped

Returns the trace object during the event.

Similar to the following, but it returns the correct object (the method receiver) for :c_call and :c_return events:

trace.binding.eval('self')