add initial SvnRunner.run_svn()

share/svi/lib/svi/svn_runner.rb

@@ -1,4 +1,91 @@
 module Svi
   module SvnRunner
+
+    # Exception class to indicate an error with executing svn.
+    class SvnExecError < RuntimeError; end
+
+    # Run Subversion and yield results linewise.
+    #
+    # @param subcommand [String, nil]
+    #   The svn subcommand to execute (e.g. "ls").
+    # @param args [Array<String>]
+    #   The svn subcommand arguments.
+    # @param options [Hash]
+    #   Optional arguments.
+    # @option options [Array<String>] :global_args
+    #   Global svn arguments to place before the subcommand.
+    #
+    # @yield [line]
+    #   If a block is given, each line that the Subversion command writes to
+    #   standard output will be yielded to the calling block.
+    # @yieldparam line [String]
+    #   Line of standard output.
+    # @return [String]
+    #   The standard output from svn.
+    # @raise [SvnExecError]
+    #   If the svn command errors out this exception is raised.
+    def run_svn(subcommand, args, options = {}, &block)
+      command = [
+        "svn",
+        *(options[:global_args] || []),
+        subcommand,
+        *args,
+      ].compact
+
+      # Create pipes for standard output and standard error.
+      stdout_rd, stdout_wr = IO.pipe
+      stderr_rd, stderr_wr = IO.pipe
+
+      # Launch the svn subprocess using the pipes.
+      spawn_options = {
+        out: stdout_wr,
+        err: stderr_wr,
+        close_others: true,
+      }
+      spawn_options[:in] = :close unless options[:allow_interactive]
+      svn_pid = Process.spawn(*command, spawn_options)
+
+      # Close write side of the pipes in the parent process.
+      stdout_wr.close
+      stderr_wr.close
+
+      stdout = ""
+      stderr = ""
+      stdout_yield = ""
+
+      loop do
+        so = stdout_rd.read_nonblock(exception: false)
+        if so.is_a?(String)
+          stdout += so
+          stdout_yield += so
+        end
+        se = stderr_rd.read_nonblock(exception: false)
+        if se.is_a?(String)
+          stderr += se
+        end
+        if so.nil? and se.nil?
+          break
+        end
+        if block
+          loop do
+            index = stdout_yield.index("\n")
+            break unless index
+            line = stdout_yield[0, index]
+            block[line]
+            stdout_yield = stdout_yield[index + 1, stdout_yield.size]
+          end
+        end
+        IO.select([stdout_rd, stderr_rd])
+      end
+
+      Process.waitpid(svn_pid)
+
+      if stderr != ""
+        raise SvnExecError.new(stderr)
+      end
+
+      stdout
+    end
+
   end
 end