class Git::SystemCallGuard

Convert ‘SystemCallError` raised by the gem’s own filesystem calls to {Git::Error}

The gem promises to raise only ‘ArgumentError` or a subclass of {Git::Error}. Filesystem calls such as `File.read`, `Dir.chdir`, or `Tempfile.create` can raise a bare `SystemCallError` (`Errno::ENOENT`, `Errno::EACCES`, and so on). Wrapping those calls in {.call} keeps the promise: the `SystemCallError` is re-raised as a {Git::Error} with the original error available as `cause`.

Helpers that yield to caller-supplied blocks must not relabel errors raised by the caller’s own code. {#unguarded} marks that region so a ‘SystemCallError` raised inside it propagates unchanged.

@example Guard a single filesystem call

content = Git::SystemCallGuard.call('Failed to read the gitdir pointer file') do
  File.read(path)
end

@example Guard setup and cleanup but not the caller’s block

def with_tempfile(&block)
  Git::SystemCallGuard.call('Failed to create a temporary file') do |guard|
    Tempfile.create do |file|
      guard.unguarded { block.call(file) }
    end
  end
end

@api private

Public Class Methods

call (message, &)

Source

# File lib/git/system_call_guard.rb, line 50
def self.call(message, &)
  new.call(message, &)
end

Run the block, converting any ‘SystemCallError` it raises to {Git::Error}

@param message [String] prefix for the {Git::Error} message

@return [Object] the value returned by the block

@raise [Git::Error] if the block raises a ‘SystemCallError` outside an

unguarded region

@yield [guard] the guarded region

@yieldparam guard [Git::SystemCallGuard] use {#unguarded} to exempt a region

@yieldreturn [Object] returned as the method’s return value

Public Instance Methods

call (message) { |self| ... }

Source

# File lib/git/system_call_guard.rb, line 68
def call(message)
  yield self
rescue SystemCallError => e
  raise if e.equal?(@unguarded_error)

  raise Git::Error, "#{message}: #{e.message}"
end

Run the block, converting any ‘SystemCallError` it raises to {Git::Error}

@param (see .call)

@return (see .call)

@raise (see .call)

@yield (see .call)

@yieldparam (see .call)

@yieldreturn (see .call)

unguarded () { || ... }

Source

# File lib/git/system_call_guard.rb, line 88
def unguarded
  yield
rescue SystemCallError => e
  @unguarded_error = e
  raise
end

Run the block with ‘SystemCallError` conversion suspended

If the block raises a ‘SystemCallError`, the enclosing {#call} re-raises that same error unchanged. Any other `SystemCallError` reaching {#call}, including one raised while unwinding from the block’s error, is converted.

@return [Object] the value returned by the block

@yield the region exempt from conversion

@yieldreturn [Object] returned as the method’s return value