RFC: remove repl prompt prefix before parsing

NEWS.md

@@ -4,6 +4,13 @@ Julia v0.6.0 Release Notes
 New language features
 ---------------------
 
+  * The REPL now supports something called *prompt pasting*.
+    This activates when pasting text that starts with `julia> ` into the REPL.
+    In that case, only expressions starting with `julia> ` are parsed, the rest are removed.
+    This makes it possible to paste a chunk of code that has been copied from a REPL session
+    without having to scrub away prompts and outputs.
+    This can be disabled or enabled at will with `Base.REPL.enable_promptpaste(::Bool)`.
+
 Language changes
 ----------------
 

base/REPL.jl

@@ -36,6 +36,8 @@ abstract AbstractREPL
 
 answer_color(::AbstractREPL) = ""
 
+const JULIA_PROMPT = "julia> "
+
 type REPLBackend
     "channel for AST"
     repl_channel::Channel
@@ -207,7 +209,7 @@ function run_frontend(repl::BasicREPL, backend::REPLBackendRef)
     hit_eof = false
     while true
         Base.reseteof(repl.terminal)
-        write(repl.terminal, "julia> ")
+        write(repl.terminal, JULIA_PROMPT)
         line = ""
         ast = nothing
         interrupted = false
@@ -692,6 +694,9 @@ end
 repl_filename(repl, hp::REPLHistoryProvider) = "REPL[$(length(hp.history)-hp.start_idx)]"
 repl_filename(repl, hp) = "REPL"
 
+const JL_PROMT_PASTE = Ref(true)
+enable_promtpaste(v::Bool) = JL_PROMT_PASTE[] = v
+
 function setup_interface(repl::LineEditREPL; hascolor = repl.hascolor, extra_repl_keymap = Dict{Any,Any}[])
     ###
     #
@@ -723,7 +728,7 @@ function setup_interface(repl::LineEditREPL; hascolor = repl.hascolor, extra_rep
     replc = REPLCompletionProvider(repl)
 
     # Set up the main Julia prompt
-    julia_prompt = Prompt("julia> ";
+    julia_prompt = Prompt(JULIA_PROMPT;
         # Copy colors from the prompt object
         prompt_prefix = hascolor ? repl.prompt_color : "",
         prompt_suffix = hascolor ?
@@ -837,7 +842,29 @@ function setup_interface(repl::LineEditREPL; hascolor = repl.hascolor, extra_rep
             input = takebuf_string(sbuffer)
             oldpos = start(input)
             firstline = true
+            isprompt_paste = false
             while !done(input, oldpos) # loop until all lines have been executed
+                if JL_PROMT_PASTE[]
+                    # Check if the next statement starts with "julia> ", in that case
+                    # skip it. But first skip whitespace
+                    while input[oldpos] in ('\n', ' ', '\t')
+                        oldpos = nextind(input, oldpos)
+                        oldpos >= sizeof(input) && return
+                    end
+                    # Check if input line starts with "julia> ", remove it if we are in prompt paste mode
+                    jl_prompt_len = 7
+                     if (firstline || isprompt_paste) && (oldpos + jl_prompt_len <= sizeof(input) && input[oldpos:oldpos+jl_prompt_len-1] == JULIA_PROMPT)
+                        isprompt_paste = true
+                        oldpos += jl_prompt_len
+                    # If we are prompt pasting and current statement does not begin with julia> , skip to next line
+                    elseif isprompt_paste
+                        while input[oldpos] != '\n'
+                            oldpos = nextind(input, oldpos)
+                            oldpos >= sizeof(input) && return
+                        end
+                        continue
+                    end
+                end
                 ast, pos = Base.syntax_deprecation_warnings(false) do
                     Base.parse(input, oldpos, raise=false)
                 end

doc/manual/interacting-with-julia.rst

@@ -42,6 +42,13 @@ There are a number useful features unique to interactive work. In addition to sh
     julia> ans
     "12"
 
+In Julia mode, the REPL supports something called *prompt pasting*. This activates when pasting text that starts with ``julia> `` into the REPL.
+In that case, only expressions starting with ``julia> `` are parsed, others are removed.
+This makes it is possible to paste a chunk of code that has been copied from a REPL session without having to scrub away prompts and outputs.
+This feature is enabled by default but can be disabled or enabled at will with ``Base.REPL.enable_promptpaste(::Bool)``.
+If it is enabled, you can try it out by pasting the code block above this paragraph straight into the REPL.
+This feature does not work on the standard Windows command prompt due to its limitation at detecting when a paste occurs.
+
 Help mode
 ~~~~~~~~~
 

test/repl.jl

@@ -397,6 +397,66 @@ begin
     # Try entering search mode while in custom repl mode
     LineEdit.enter_search(s, custom_histp, true)
 end
+
+# Test removal of prompt in bracket pasting
+begin
+    stdin_write, stdout_read, stderr_read, repl = fake_repl()
+
+    repl.interface = REPL.setup_interface(repl)
+    repl_mode = repl.interface.modes[1]
+    shell_mode = repl.interface.modes[2]
+    help_mode = repl.interface.modes[3]
+
+    repltask = @async begin
+        Base.REPL.run_repl(repl)
+    end
+
+    c = Condition()
+
+    sendrepl2(cmd) = write(stdin_write,"$cmd\n notify(c)\n")
+
+    # Test removal of prefix in single statement paste
+    sendrepl2("\e[200~julia> A = 2\e[201~\n")
+    wait(c)
+    @test A == 2
+
+    # Test removal of prefix in multiple statement paste
+    sendrepl2("""\e[200~
+            julia> type T17599; a::Int; end
+
+            julia> function foo(julia)
+            julia> 3
+                end
+
+                    julia> A = 3\e[201~
+             """)
+    wait(c)
+    @test A == 3
+    @test foo(4)
+    @test T17599(3).a == 3
+    @test !foo(2)
+
+    sendrepl2("""\e[200~
+            julia> goo(x) = x + 1
+            error()
+
+            julia> A = 4
+            4\e[201~
+             """)
+    wait(c)
+    @test A == 4
+    @test goo(4) == 5
+
+    # Test prefix removal only active in bracket paste mode
+    sendrepl2("julia = 4\n julia> 3 && (A = 1)\n")
+    wait(c)
+    @test A == 1
+
+    # Close repl
+    write(stdin_write, '\x04')
+    wait(repltask)
+end
+
 # Simple non-standard REPL tests
 if !is_windows() || Sys.windows_version() >= Sys.WINDOWS_VISTA_VER
     stdin_write, stdout_read, stdout_read, repl = fake_repl()