Start to Add WASM Support Again (#14418)

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# Description
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The [nushell/demo](https://github.com/nushell/demo) project successfully
demonstrated running Nushell in the browser using WASM. However, the
current version of Nushell cannot be easily built for the
`wasm32-unknown-unknown` target, the default for `wasm-bindgen`.

This PR introduces initial support for the `wasm32-unknown-unknown`
target by disabling OS-dependent features such as filesystem access, IO,
and platform/system-specific functionality. This separation is achieved
using a new `os` feature in the following crates:

 - `nu-cmd-lang`
 - `nu-command`
 - `nu-engine`
 - `nu-protocol`

The `os` feature includes all functionality that interacts with an
operating system. It is enabled by default, but can be disabled using
`--no-default-features`. All crates that depend on these core crates now
use `--no-default-features` to allow compilation for WASM.

To demonstrate compatibility, the following script builds all crates
expected to work with WASM. Direct user interaction, running external
commands, working with plugins, and features requiring `openssl` are out
of scope for now due to their complexity or reliance on C libraries,
which are difficult to compile and link in a WASM environment.

```nushell
[ # compatible crates
	"nu-cmd-base",
	"nu-cmd-extra",
	"nu-cmd-lang",
	"nu-color-config",
	"nu-command",
	"nu-derive-value",
	"nu-engine",
	"nu-glob",
	"nu-json",
	"nu-parser",
	"nu-path",
	"nu-pretty-hex",
	"nu-protocol",
	"nu-std",
	"nu-system",
	"nu-table",
	"nu-term-grid",
	"nu-utils",
	"nuon"
] | each {cargo build -p $in --target wasm32-unknown-unknown --no-default-features}
```

## Caveats
This PR has a few caveats:
1. **`miette` and `terminal-size` Dependency Issue**
`miette` depends on `terminal-size`, which uses `rustix` when the target
is not Windows. However, `rustix` requires `std::os::unix`, which is
unavailable in WASM. To address this, I opened a
[PR](https://github.com/eminence/terminal-size/pull/68) for
`terminal-size` to conditionally compile `rustix` only when the target
is Unix. For now, the `Cargo.toml` includes patches to:
    - Use my forked version of `terminal-size`.
- ~~Use an unreleased version of `miette` that depends on
`terminal-size@0.4`.~~

These patches are temporary and can be removed once the upstream changes
are merged and released.

2. **Test Output Adjustments**
Due to the slight bump in the `miette` version, one test required
adjustments to accommodate minor formatting changes in the error output,
such as shifted newlines.

# User-Facing Changes
<!-- List of all changes that impact the user experience here. This
helps us keep track of breaking changes. -->
This shouldn't break anything but allows using some crates for targeting
`wasm32-unknown-unknown` to revive the demo page eventually.

# Tests + Formatting
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- `cargo test --workspace` to check that all tests pass (on Windows make
sure to [enable developer
mode](https://learn.microsoft.com/en-us/windows/apps/get-started/developer-mode-features-and-debugging))
- `cargo run -- -c "use toolkit.nu; toolkit test stdlib"` to run the
tests for the standard library

> **Note**
> from `nushell` you can also use the `toolkit` as follows
> ```bash
> use toolkit.nu # or use an `env_change` hook to activate it
automatically
> toolkit check pr
> ```
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- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

I did not add any extra tests, I just checked that compiling works, also
when using the host target but unselecting the `os` feature.

# After Submitting
<!-- If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.
-->
~~Breaking the wasm support can be easily done by adding some `use`s or
by adding a new dependency, we should definitely add some CI that also
at least builds against wasm to make sure that building for it keep
working.~~
I added a job to build wasm.

---------

Co-authored-by: Ian Manske <ian.manske@pm.me>

crates/nu-command/src/env/config/config_.rs

@@ -1,4 +1,6 @@
-use nu_engine::{command_prelude::*, get_full_help};
+use nu_cmd_base::util::get_editor;
+use nu_engine::{command_prelude::*, env_to_strings, get_full_help};
+use nu_system::ForegroundChild;
 
 #[derive(Clone)]
 pub struct ConfigMeta;
@@ -36,3 +38,79 @@ impl Command for ConfigMeta {
         vec!["options", "setup"]
     }
 }
+
+#[cfg(not(feature = "os"))]
+pub(super) fn start_editor(
+    _: &'static str,
+    _: &EngineState,
+    _: &mut Stack,
+    call: &Call,
+) -> Result<PipelineData, ShellError> {
+    Err(ShellError::DisabledOsSupport {
+        msg: "Running external commands is not available without OS support.".to_string(),
+        span: Some(call.head),
+    })
+}
+
+#[cfg(feature = "os")]
+pub(super) fn start_editor(
+    config_path: &'static str,
+    engine_state: &EngineState,
+    stack: &mut Stack,
+    call: &Call,
+) -> Result<PipelineData, ShellError> {
+    // Find the editor executable.
+    let (editor_name, editor_args) = get_editor(engine_state, stack, call.head)?;
+    let paths = nu_engine::env::path_str(engine_state, stack, call.head)?;
+    let cwd = engine_state.cwd(Some(stack))?;
+    let editor_executable =
+        crate::which(&editor_name, &paths, cwd.as_ref()).ok_or(ShellError::ExternalCommand {
+            label: format!("`{editor_name}` not found"),
+            help: "Failed to find the editor executable".into(),
+            span: call.head,
+        })?;
+
+    let Some(config_path) = engine_state.get_config_path(config_path) else {
+        return Err(ShellError::GenericError {
+            error: format!("Could not find $nu.{config_path}"),
+            msg: format!("Could not find $nu.{config_path}"),
+            span: None,
+            help: None,
+            inner: vec![],
+        });
+    };
+    let config_path = config_path.to_string_lossy().to_string();
+
+    // Create the command.
+    let mut command = std::process::Command::new(editor_executable);
+
+    // Configure PWD.
+    command.current_dir(cwd);
+
+    // Configure environment variables.
+    let envs = env_to_strings(engine_state, stack)?;
+    command.env_clear();
+    command.envs(envs);
+
+    // Configure args.
+    command.arg(config_path);
+    command.args(editor_args);
+
+    // Spawn the child process. On Unix, also put the child process to
+    // foreground if we're in an interactive session.
+    #[cfg(windows)]
+    let child = ForegroundChild::spawn(command)?;
+    #[cfg(unix)]
+    let child = ForegroundChild::spawn(
+        command,
+        engine_state.is_interactive,
+        &engine_state.pipeline_externals_state,
+    )?;
+
+    // Wrap the output into a `PipelineData::ByteStream`.
+    let child = nu_protocol::process::ChildProcess::new(child, None, false, call.head)?;
+    Ok(PipelineData::ByteStream(
+        ByteStream::child(child, call.head),
+        None,
+    ))
+}

crates/nu-command/src/env/config/config_env.rs

@@ -1,7 +1,4 @@
-use nu_cmd_base::util::get_editor;
-use nu_engine::{command_prelude::*, env_to_strings};
-use nu_protocol::{process::ChildProcess, ByteStream};
-use nu_system::ForegroundChild;
+use nu_engine::command_prelude::*;
 
 #[derive(Clone)]
 pub struct ConfigEnv;
@@ -81,60 +78,6 @@ impl Command for ConfigEnv {
             return Ok(Value::string(nu_utils::get_sample_env(), head).into_pipeline_data());
         }
 
-        // Find the editor executable.
-        let (editor_name, editor_args) = get_editor(engine_state, stack, call.head)?;
-        let paths = nu_engine::env::path_str(engine_state, stack, call.head)?;
-        let cwd = engine_state.cwd(Some(stack))?;
-        let editor_executable = crate::which(&editor_name, &paths, cwd.as_ref()).ok_or(
-            ShellError::ExternalCommand {
-                label: format!("`{editor_name}` not found"),
-                help: "Failed to find the editor executable".into(),
-                span: call.head,
-            },
-        )?;
-
-        let Some(env_path) = engine_state.get_config_path("env-path") else {
-            return Err(ShellError::GenericError {
-                error: "Could not find $nu.env-path".into(),
-                msg: "Could not find $nu.env-path".into(),
-                span: None,
-                help: None,
-                inner: vec![],
-            });
-        };
-        let env_path = env_path.to_string_lossy().to_string();
-
-        // Create the command.
-        let mut command = std::process::Command::new(editor_executable);
-
-        // Configure PWD.
-        command.current_dir(cwd);
-
-        // Configure environment variables.
-        let envs = env_to_strings(engine_state, stack)?;
-        command.env_clear();
-        command.envs(envs);
-
-        // Configure args.
-        command.arg(env_path);
-        command.args(editor_args);
-
-        // Spawn the child process. On Unix, also put the child process to
-        // foreground if we're in an interactive session.
-        #[cfg(windows)]
-        let child = ForegroundChild::spawn(command)?;
-        #[cfg(unix)]
-        let child = ForegroundChild::spawn(
-            command,
-            engine_state.is_interactive,
-            &engine_state.pipeline_externals_state,
-        )?;
-
-        // Wrap the output into a `PipelineData::ByteStream`.
-        let child = ChildProcess::new(child, None, false, call.head)?;
-        Ok(PipelineData::ByteStream(
-            ByteStream::child(child, call.head),
-            None,
-        ))
+        super::config_::start_editor("env-path", engine_state, stack, call)
     }
 }

crates/nu-command/src/env/config/config_nu.rs

@@ -1,7 +1,4 @@
-use nu_cmd_base::util::get_editor;
-use nu_engine::{command_prelude::*, env_to_strings};
-use nu_protocol::{process::ChildProcess, ByteStream};
-use nu_system::ForegroundChild;
+use nu_engine::command_prelude::*;
 
 #[derive(Clone)]
 pub struct ConfigNu;
@@ -83,60 +80,6 @@ impl Command for ConfigNu {
             return Ok(Value::string(nu_utils::get_sample_config(), head).into_pipeline_data());
         }
 
-        // Find the editor executable.
-        let (editor_name, editor_args) = get_editor(engine_state, stack, call.head)?;
-        let paths = nu_engine::env::path_str(engine_state, stack, call.head)?;
-        let cwd = engine_state.cwd(Some(stack))?;
-        let editor_executable = crate::which(&editor_name, &paths, cwd.as_ref()).ok_or(
-            ShellError::ExternalCommand {
-                label: format!("`{editor_name}` not found"),
-                help: "Failed to find the editor executable".into(),
-                span: call.head,
-            },
-        )?;
-
-        let Some(config_path) = engine_state.get_config_path("config-path") else {
-            return Err(ShellError::GenericError {
-                error: "Could not find $nu.config-path".into(),
-                msg: "Could not find $nu.config-path".into(),
-                span: None,
-                help: None,
-                inner: vec![],
-            });
-        };
-        let config_path = config_path.to_string_lossy().to_string();
-
-        // Create the command.
-        let mut command = std::process::Command::new(editor_executable);
-
-        // Configure PWD.
-        command.current_dir(cwd);
-
-        // Configure environment variables.
-        let envs = env_to_strings(engine_state, stack)?;
-        command.env_clear();
-        command.envs(envs);
-
-        // Configure args.
-        command.arg(config_path);
-        command.args(editor_args);
-
-        // Spawn the child process. On Unix, also put the child process to
-        // foreground if we're in an interactive session.
-        #[cfg(windows)]
-        let child = ForegroundChild::spawn(command)?;
-        #[cfg(unix)]
-        let child = ForegroundChild::spawn(
-            command,
-            engine_state.is_interactive,
-            &engine_state.pipeline_externals_state,
-        )?;
-
-        // Wrap the output into a `PipelineData::ByteStream`.
-        let child = ChildProcess::new(child, None, false, call.head)?;
-        Ok(PipelineData::ByteStream(
-            ByteStream::child(child, call.head),
-            None,
-        ))
+        super::config_::start_editor("config-path", engine_state, stack, call)
     }
 }