REPL shell mode for Windows

Introduce REPL shell mode on Windows.

Co-authored-by:    Mustafa M. <[email protected]>
Co-authored-by:    Jameson Nash <[email protected]>

base/Base.jl

@@ -174,8 +174,8 @@ include("iobuffer.jl")
 include("intfuncs.jl")
 include("strings/strings.jl")
 include("parse.jl")
-include("shell.jl")
 include("regex.jl")
+include("shell.jl")
 include("show.jl")
 include("arrayshow.jl")
 include("methodshow.jl")

base/client.jl

@@ -31,24 +31,26 @@ stackframe_lineinfo_color() = repl_color("JULIA_STACKFRAME_LINEINFO_COLOR", :bol
 stackframe_function_color() = repl_color("JULIA_STACKFRAME_FUNCTION_COLOR", :bold)
 
 function repl_cmd(cmd, out)
-    shell = shell_split(get(ENV, "JULIA_SHELL", get(ENV, "SHELL", "/bin/sh")))
+    shell_env = get(ENV, "JULIA_SHELL", nothing)
+    if shell_env === nothing || isempty(shell_env)
+        shell_env = Sys.iswindows() ? "cmd" : get(ENV, "SHELL", "/bin/sh")
+    end
+    shell = shell_split(shell_env)
     shell_name = Base.basename(shell[1])
+    Sys.iswindows() && (shell_name = lowercase(splitext(shell_name)[1])) # canonicalize for comparisons below
 
     # Immediately expand all arguments, so that typing e.g. ~/bin/foo works.
     cmd.exec .= expanduser.(cmd.exec)
+    isempty(cmd.exec) && throw(ArgumentError("no cmd to execute"))
 
-    if isempty(cmd.exec)
-        throw(ArgumentError("no cmd to execute"))
-    elseif cmd.exec[1] == "cd"
+    if cmd.exec[1] == "cd"
         new_oldpwd = pwd()
         if length(cmd.exec) > 2
             throw(ArgumentError("cd method only takes one argument"))
         elseif length(cmd.exec) == 2
             dir = cmd.exec[2]
             if dir == "-"
-                if !haskey(ENV, "OLDPWD")
-                    error("cd: OLDPWD not set")
-                end
+                !haskey(ENV, "OLDPWD") && error("cd: OLDPWD not set")
                 cd(ENV["OLDPWD"])
             else
                 @static if !Sys.iswindows()
@@ -66,19 +68,51 @@ function repl_cmd(cmd, out)
         ENV["OLDPWD"] = new_oldpwd
         println(out, pwd())
     else
-        @static if !Sys.iswindows()
+        local command
+        if Sys.iswindows()
+            if shell_name == "cmd"
+                _CMD_execute(cmd)
+            elseif shell_name in ("powershell", "pwsh")
+                _powershell_cmd(cmd)
+            elseif shell_name == "busybox"
+                command = `$shell sh -c $(shell_escape_posixly(cmd))`
+            else
+                command = `$shell $cmd`
+            end
+        else
             if shell_name == "fish"
                 shell_escape_cmd = "begin; $(shell_escape_posixly(cmd)); and true; end"
+            elseif shell_name == "pwsh"
+                _powershell_cmd(cmd)
             else
                 shell_escape_cmd = "($(shell_escape_posixly(cmd))) && true"
             end
-            cmd = `$shell -c $shell_escape_cmd`
+            command = `$shell -c $shell_escape_cmd`
         end
-        run(ignorestatus(cmd))
+        run(ignorestatus(command))
     end
     nothing
 end
 
+# process cmd's passed to CMD
+_CMD_execute(cmd) = Cmd(`$shell /c $(shell_escape_CMDly(shell_escape_winsomely(cmd)))`, windows_verbatim=true)
+
+function _powershell_execute(cmd)
+    # process cmd's passed to powershell
+    CommandType = nothing
+    try
+        CommandType = readchomp(`$shell -Command "Get-Command -- $(shell_escape_PWSH_cmdlet_ly(cmd.exec[1])) | Select-Object -ExpandProperty CommandType"`)
+    catch
+    end
+    # TODO: while CommandType == "Alias"; CommandType = ...; end
+    if CommandType == "Application"
+        command = Cmd(`$shell -Command "& $(shell_escape_PWSHly(shell_escape_winsomely(cmd)))"`)
+    else # handle Function and Cmdlet # TODO: what is the proper handling for the other types (ExternalScript, Script, Workflow, Configuration, and Filter)
+        command = Cmd(`$shell -Command "& $(shell_escape_PWSH_cmdlet_ly(cmd))"`)
+    end
+    return command
+end
+
 # deprecated function--preserved for DocTests.jl
 function ip_matches_func(ip, func::Symbol)
     for fr in StackTraces.lookup(ip)

base/cmd.jl

@@ -98,12 +98,10 @@ end
 hash(x::AndCmds, h::UInt) = hash(x.a, hash(x.b, h))
 ==(x::AndCmds, y::AndCmds) = x.a == y.a && x.b == y.b
 
-shell_escape(cmd::Cmd; special::AbstractString="") =
-    shell_escape(cmd.exec..., special=special)
-shell_escape_posixly(cmd::Cmd) =
-    shell_escape_posixly(cmd.exec...)
-shell_escape_winsomely(cmd::Cmd) =
-    shell_escape_winsomely(cmd.exec...)
+shell_escape(cmd::Cmd; special::AbstractString="") = shell_escape(cmd.exec..., special=special)
+shell_escape_posixly(cmd::Cmd) = shell_escape_posixly(cmd.exec...)
+shell_escape_winsomely(cmd::Cmd) = shell_escape_winsomely(cmd.exec...)
+shell_escape_PWSH_cmdlet_ly(cmd::Cmd) = shell_escape_PWSH_cmdlet_ly(cmd.exec...)
 
 function show(io::IO, cmd::Cmd)
     print_env = cmd.env !== nothing

base/shell.jl

@@ -292,7 +292,7 @@ end
 
 
 """
-     shell_escaped_winsomely(args::Union{Cmd,AbstractString...})::String
+     shell_escaped_winsomely(args::Union{Cmd,AbstractString...}) -> String
 
 Convert the collection of strings `args` into single string suitable for passing as the argument
 string for a Windows command line. Windows passes the entire command line as a single string to
@@ -312,3 +312,69 @@ julia> println(shell_escaped_winsomely("A B\\", "C"))
 """
 shell_escape_winsomely(args::AbstractString...) =
     sprint(print_shell_escaped_winsomely, args..., sizehint=(sum(length, args)) + 3*length(args))
+
+function print_shell_escaped_CMDly(io::IO, arg::AbstractString)
+    any(c -> c in ('\r', '\n'), arg) && throw(ArgumentError("Encountered unsupported character by CMD."))
+    # include " so to avoid toggling behavior of ^
+    arg = replace(arg, r"[%!^\"<>&|]" => s"^\0")
+    print(io, arg)
+end
+
+"""
+     shell_escape_CMDly(arg::AbstractString) -> String
+
+The unexported `shell_escape_CMDly` function takes a string and escapes any special characters
+in such a way that it is safe to pass it as an argument to some `CMD.exe`. This may be useful
+in concert with the `windows_verbatim` flag to [`Cmd`](@ref) when constructing process
+pipelines.
+
+See also [`shell_escape_PWSHly`](@ref).
+
+# Example
+```jldoctest
+julia> println(shell_escape_CMDly("\"A B\\\" & C"))
+^"A B\\^" ^& C
+
+!important
+    Due to a peculiar behavior of the CMD, each command after a literal `|` character
+    (indicating a command pipeline) must have `shell_escape_CMDly` applied twice. For example:
+    ```
+    to_print = "All for 1 & 1 for all!"
+    run(Cmd(Cmd(["cmd /c \"break | echo \$(shell_escape_CMDly(shell_escape_CMDly(to_print)))"]), windows_verbatim=true))
+    ```
+"""
+shell_escape_CMDly(arg::AbstractString) = sprint(print_shell_escaped_CMDly, arg)
+
+function print_shell_escaped_PWSHly(io::IO, arg::AbstractString)
+    # escape several characters that usually have special meaning
+    arg = replace(arg, r"[`\"\$#;|><&(){}=]" => s"`\0")
+    # escape special control chars
+    arg = replace(replace(replace(arg, '\r' => "`r"), '\t' => "`t"), '\t' => "`t")
+    print(io, arg)
+end
+
+"""
+     shell_escape_PWSHly(arg::AbstractString) -> String
+
+Escapes special characters so they can be appropriately used with PowerShell.
+
+See also [`shell_escape_CMDly`](@ref).
+"""
+shell_escape_PWSHly(arg::AbstractString) = sprint(print_shell_escaped_PWSHly, arg)
+
+function print_shell_escaped_PWSH_cmdlet_ly(io::IO, args::AbstractString...)
+    # often the shortest way to escape a powershell string is to double any single quotes and then wrap the whole thing in single quotes
+    # (alternatively, we could prefix all the non-word characters with a back-tick and replace newlines with `r and `n)
+    # but skip the escaping for common cases we always know are safe (e.g. so that named parameters are typically still interpreted correctly)
+    isword(c::AbstractChar) = '0' <= c <= '9' || 'a' <= c <= 'z' || 'A' <= c <= 'Z' || c == '_' || c == '\\' || c == ':' || c == '/' || c == '-'
+    join(io, (all(isword, arg) ? arg : string("'", replace(arg, "'" => "''"), "'") for arg in args), " ")
+end
+
+"""
+    shell_escape_PWSH_cmdlet_ly(args::AbstractString...) -> String
+
+Escapes special characters so they can be appropriately used with a PowerShell cmdlet (such as `echo`).
+
+See also [`shell_escape_PWSHly`](@ref) and [`shell_escape_winsomely`](@ref).
+"""
+shell_escape_PWSH_cmdlet_ly(args::AbstractString...) = sprint(print_shell_escaped_PWSH_cmdlet_ly, args...)

doc/src/manual/environment-variables.md

@@ -168,10 +168,9 @@ The absolute path of the shell with which Julia should execute external commands
 (via `Base.repl_cmd()`). Defaults to the environment variable `$SHELL`, and
 falls back to `/bin/sh` if `$SHELL` is unset.
 
-!!! note
-
-    On Windows, this environment variable is ignored, and external commands are
-    executed directly.
+On Windows, `$JULIA_SHELL` can be set to `cmd`, `powershell`, `busybox` or `""`.
+If set to `""` external commands are executed directly. Defaults to `cmd` if
+`$JULIA_SHELL` is not set.
 
 ### `JULIA_EDITOR`
 

stdlib/REPL/docs/src/index.md

@@ -103,6 +103,7 @@ julia> ; # upon typing ;, the prompt changes (in place) to: shell>
 shell> echo hello
 hello
 ```
+See `JULIA_SHELL` in the Environment Variables section of the Julia manual.
 
 ### Search modes