process.spawn: add stdio options and environment variables

.seal/guided_tour.luau

@@ -127,8 +127,7 @@ type SpawningChildProcesses = {}; local back: TableOfContents do
 		args = { "--version" }
 	}
 
-	print(if result.ok then result.stdout
-          else result.stderr)
+	print(if result.ok then result.stdout else result.stderr)
 	-- if you want to assume your process run attempt succeeded (and error otherwise), use :unwrap()
 	local stdout = result:unwrap()
 
@@ -142,7 +141,7 @@ type SpawningChildProcesses = {}; local back: TableOfContents do
 	local handle = process.spawn {
 		program = `seal eval '{waiting_src}'`,
 		shell = if env.os == "Windows" then "pwsh" else "sh"
-	}
+	} :: process.PipedChild
 
 	local text = ""
 	while handle:alive() do

.seal/typedefs/std/process.luau

@@ -29,7 +29,7 @@
     local child = process.spawn({
         program = "someutil --watch",
         shell = "sh",
-    })
+    }) :: process.PipedChild
 
     for line in child.stdout:lines() do
         local thing_changed = line:match("([%w]+) changed!")
@@ -97,25 +97,30 @@ export type process = {
     shell: (command: string) -> RunResult,
     --[=[
     Spawns a long-running process in a non-blocking manner, returns a `ChildProcess` that contains handles to the spawned process' stdout, stderr, and stdin.
+
+    There are three primary usecases for `process.spawn`:
+    1. Listening to the output of a long-running process.
+    2. Running another program in the background while your program does work.
+    3. Launching multiple instances of the same program in parallel.
 
     ## Usage
 
-    A long-running program you want to listen to.
+    Listen to the output of a long-running process:
 
     ```luau
     local process = require("@std/process")
     local child = process.spawn({
         program = "someutil --watch",
         shell = "sh",
-    })
+    }) :: process.PipedChild
 
     for line in child.stdout:lines() do
         local thing_changed = line:match("([%w]+) changed!")
         print(`Change detected: {thing_changed}`)
     end
     ```
 
-    Run multiple processes at the same time to finish faster.
+    Run multiple processes at the same time to finish faster:
 
     For example, `markdownlint-cli2` takes about 0.3 seconds to fix a file, so if you have 20+ files, and you
     fix each file one-at-a-time with `process.run`, it'll take 6+ seconds to do all files.
@@ -125,14 +130,14 @@ export type process = {
 
     ```luau
     local paths: { string } = get_files()
-    -- make a threadpool to keep track of what files are finished
-    local handles: { [string]: process.ThreadHandle } = {}
+    -- make a childpool to keep track of what files are finished
+    local handles: { [string]: process.PipedChild } = {}
 
     for _, path in paths do
         local handle = process.spawn {
             program = "markdownlint-cli2",
             args = { "--fix", path }
-        }
+        } :: process.PipedChild
         handles[path] = handle
     end
 
@@ -148,10 +153,6 @@ export type process = {
     ```
     ]=]
     spawn: (options: SpawnOptions) -> ChildProcess,
-    --[=[
-        Doesn't work.
-    ]=]
-    setexitcallback: ((number) -> ()) -> (),
     --[=[
         Immediately terminate the current program with exit `code`.
 
@@ -193,26 +194,97 @@ export type Err = {
     stderr: string,
 }
 
+export type Stdio = "Pipe" | "Inherit" | "Ignore"
+
+--[=[
+    Options for `process.run`; implicitly added to `process.shell` as well.
+]=]
 export type RunOptions = {
+    --- the program you want to run, must be available in $PATH or be an absolute path to an executable
     program: string,
     --- an optional list of arguments to pass into the program; on Windows, you should use this instead of trying to pass whitespace-separated arguments in `program`
     args: { string }?,
-    --- specify a shell to run the program with; otherwise runs it as a bare process with no shell
-    shell: string?,
+    --[=[
+        Specify a shell to run `program` with; if unspecified or nil, 
+        defaults to running it as a bare process with no shell (behavior may differ on Windows vs. Unix-like).
+
+        If `shell == true`, performs some magic (like checking `$SHELL`) to try and figure out
+        what your current shell is, defaulting to WindowsPowerShell on Windows and `sh` on Unix-like.
+
+        Be careful with shell escapes w/ user-provided values; can be a security risk.
+    ]=]
+    shell: (true | string)?,
     --- path to the the working directory you want your command to execute in, defaults to your shell's cwd
     cwd: string?,
+    --[=[
+        Control whether the child process reads and writes to its own terminal (`"Pipe"`) or
+        to the terminal you're running *seal* in (`"Inherit"`).
+
+        By default, stdio is *piped*; this means the process reads and writes from separate
+        stdin, stdout, and stderr streams that you can read once the process completes.
+
+        If you want everything the process says to be displayed on your terminal (and not
+        read from the process programmatically), use `"Inherit"`.
+
+        If you want anything the process says to get ignored (redirected to `/dev/null`), use `"Ignore"`.
+
+        This field `stdio` can be either a string (if you want all streams to share the same behavior)
+        or a table (if you want different per-stream behavior).
+    ]=]
+    stdio: {
+        stdout: Stdio?,
+        stderr: Stdio?,
+        stdin: Stdio?,
+    }? | Stdio?,
+    --[=[
+        Override environment variables of the spawned `ChildProcess`.
+        By default, the spawned process inherits its environment from the current process;
+        so all environment variables visible to *seal* will be visible to it unless removed or cleared.
+
+        - To clear *all* environment variables for the spawned `ChildProcess` so
+        that the spawned process does not inherit from *seal*'s environment, set `env.clear = true`.
+        - To add additional environment variables, define a map of them (`{ [string]: string }`)
+        in `env.add`.
+        - To prevent specific environment variables from being inherited 
+        by the child process, list them in `env.remove`.
+
+        The order is clear, add, remove (so clearing the environment doesn't prevent variables from being
+        added).
+
+        ## Errors
+
+        - if you pass a table to `env` without keys `clear`, `add`, and/or `remove`.
+        - if `env.add` is present and isn't `{ [string]: string }` 
+        - if `env.remove` is present and isn't `{ string }`.
+    ]=]
+    env: {
+        clear: boolean?,
+        add: {
+            [string]: string
+        }?,
+        remove: { string }?,
+    }?
 }
 
 export type SpawnOptions = {
     --- the program you want to run, must be available in $PATH or be an absolute path to an executable
     program: string,
     --- an optional list of arguments to pass into the program; on Windows, you should use this instead of trying to pass whitespace-separated arguments in `program`
     args: { string }?,
-    shell: string?,
+    --[=[
+        Specify a shell to run `program` with; if unspecified or nil, 
+        defaults to running it as a bare process with no shell (behavior may differ on Windows vs. Unix-like).
+
+        If `shell == true`, performs some magic (like checking `$SHELL`) to try and figure out
+        what your current shell is, defaulting to WindowsPowerShell on Windows and `sh` on Unix-like.
+
+        Be careful with shell escapes w/ user-provided values; can be a security risk.
+    ]=]
+    shell: (true | string)?,
     --- path to the the working directory you want your command to execute in, defaults to your shell's cwd
     cwd: string?,
     --[=[
-        A `ChildProcessStream` captures incoming bytes from your `ChildProcess`' output streams (either stdout or stderr),
+        A `ChildProcessStream` captures incoming bytes from a `ChildProcess`' output stream (either stdout or stderr),
         and caches them in its `inner` buffer. Each stream is spawned in a separate Rust thread to facilitate
         consistently nonblocking, dependable reads, allowing most `ChildProcess.stream:read` methods to be fully nonblocking unless
         specifically requested otherwise.
@@ -243,11 +315,60 @@ export type SpawnOptions = {
         stdout_capacity: number?,
         --- inner buffer capacity of `ChildProcess.stderr`, default 1024
         stderr_capacity: number?,
-        --- what side of stdout should be truncated when full? defaults to "front"
-        stdout_truncate: ("front" | "back")?,
-        --- what side of stderr should be truncated when full? defaults to "front"
-        stderr_truncate: ("front" | "back")?,
+        --- what side of stdout should be truncated when full? defaults to "Front"
+        stdout_truncate: ("Front" | "Back")?,
+        --- what side of stderr should be truncated when full? defaults to "Front"
+        stderr_truncate: ("Front" | "Back")?,
     }?,
+    --[=[
+        Control whether the child process reads and writes to its own terminal (`"Pipe"`) or
+        to the terminal you're running *seal* in (`"Inherit"`).
+
+        By default, the child process's stdio is *piped*; this means the process
+        reads and writes from separate stdin, stdout, and stderr streams that you 
+        can access through the `ChildProcessStream` API.
+
+        If you want everything the process says to be displayed on your terminal (and not
+        read from the process programmatically), use `"Inherit"`.
+
+        If you want anything the `ChildProcess` says to get ignored (redirected to `/dev/null`), use `"Ignore"`.
+
+        This field `stdio` can be either a string (if you want all streams to share the same behavior)
+        or a table (if you want different per-stream behavior).
+    ]=]
+    stdio: {
+        stdout: Stdio?,
+        stderr: Stdio?,
+        stdin: Stdio?,
+    }? | Stdio?,
+    --[=[
+        Override environment variables of the spawned `ChildProcess`.
+        By default, the spawned process inherits its environment from the current process;
+        so all environment variables visible to *seal* will be visible to it unless removed or cleared.
+
+        - To clear *all* environment variables for the spawned `ChildProcess` so
+        that the spawned process does not inherit from *seal*'s environment, set `env.clear = true`.
+        - To add additional environment variables, define a map of them (`{ [string]: string }`)
+        in `env.add`.
+        - To prevent specific environment variables from being inherited 
+        by the child process, list them in `env.remove`.
+
+        The order is clear, add, remove (so clearing the environment doesn't prevent variables from being
+        added).
+
+        ## Errors
+
+        - if you pass a table to `env` without keys `clear`, `add`, and/or `remove`.
+        - if `env.add` is present and isn't `{ [string]: string }` 
+        - if `env.remove` is present and isn't `{ string }`.
+    ]=]
+    env: {
+        clear: boolean?,
+        add: {
+            [string]: string
+        }?,
+        remove: { string }?,
+    }?
 }
 --- Represents the stdout and stderr streams of a `ChildProcess`, both ran in parallel threads
 --- and streamed for nonblocking behavior.
@@ -433,7 +554,7 @@ export type ChildProcessStream = setmetatable<{
         local child = process.spawn({
             program = "someutil --watch",
             shell = "sh",
-        })
+        }) :: process.PipedChild
 
         for line in child.stdout:lines() do
             local thing_changed = line:match("([%w]+) changed!")
@@ -450,9 +571,11 @@ export type ChildProcessStream = setmetatable<{
             shell = "sh",
         }
 
-        local next_line = child.stdout:lines()
-        local first_line = next_line()
-        local second_line = next_line()
+        if child.stdout then
+            local next_line = child.stdout:lines()
+            local first_line = next_line()
+            local second_line = next_line()
+        end
         ```
     ]=]
     lines: (self: ChildProcessStream, timeout: number?) -> (() -> string),
@@ -495,19 +618,42 @@ type ChildProcessStdin = {
         ```luau
         local child = process.spawn {
             program = "python3",
-            args = { "-" },
+            args = { "-" }, -- allows python3 to accept source code from stdin
         }
+        assert(child.stdin ~= nil, "stdin is piped")
+
         child.stdin:write(PYTHON_SRC)
-        child.stdin:close()
+        child.stdin:close() -- send EOF to python so it evaluates the source code
         ```
     ]=]
     close: (self: ChildProcessStdin) -> (),
 }
 
+--[=[
+    A handle to a child process created by `process.spawn`, with optional handles
+    to the child's stdout, stderr, and stdin output/input streams.
+
+    By default, stdout, stderr, and stdin are piped; cast the result of `process.spawn` to
+    `process.PipedChild` to reflect this.
+]=]
 export type ChildProcess = {
+    --- The process id (`pid`) of the spawned `ChildProcess`
+    id: number,
+    alive: (self: ChildProcess | PipedChild) -> boolean,
+    kill: (self: ChildProcess | PipedChild) -> (),
+    stdout: ChildProcessStream?,
+    stderr: ChildProcessStream?,
+    stdin: ChildProcessStdin?,
+}
+
+--[=[
+    Default kind of `ChildProcess` created by `process.spawn` pipes for stdout, stderr, and stdin.
+]=]
+export type PipedChild = {
+    --- The process id (`pid`) of the spawned `ChildProcess`
     id: number,
-    alive: (self: ChildProcess) -> boolean,
-    kill: (self: ChildProcess) -> (),
+    alive: (self: ChildProcess | PipedChild) -> boolean,
+    kill: (self: ChildProcess | PipedChild) -> (),
     stdout: ChildProcessStream,
     stderr: ChildProcessStream,
     stdin: ChildProcessStdin,

.vscode/settings.json

@@ -34,4 +34,5 @@
   },
   "luau-lsp.inlayHints.variableTypes": false,
   "luau-lsp.plugin.enabled": false,
+  "stylua.disableVersionCheck": true,
 }