Defer isatty in the adapter til needed (bytecodealliance#7544)

This commit slims down the default WASI interfaces needed by the adapter by deferring the need to infer whether a stdio stream is a tty until it's requested.
alexcrichton · Nov 15, 2023 · e74b5c9 · e74b5c9
1 parent 82c3e0a
commit e74b5c9
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Showing 2 changed files with 22 additions and 28 deletions.
diff --git a/crates/wasi-preview1-component-adapter/src/descriptors.rs b/crates/wasi-preview1-component-adapter/src/descriptors.rs
@@ -94,22 +94,29 @@ impl Streams {
 
 pub enum StreamType {
     /// Streams for implementing stdio.
-    Stdio(IsATTY),
+    Stdio(Stdio),
 
     /// Streaming data with a file.
     File(File),
 }
 
-pub enum IsATTY {
-    Yes,
-    No,
+pub enum Stdio {
+    Stdin,
+    Stdout,
+    Stderr,
 }
 
-impl IsATTY {
+impl Stdio {
     pub fn filetype(&self) -> wasi::Filetype {
-        match self {
-            IsATTY::Yes => wasi::FILETYPE_CHARACTER_DEVICE,
-            IsATTY::No => wasi::FILETYPE_UNKNOWN,
+        let is_terminal = match self {
+            Stdio::Stdin => terminal_stdin::get_terminal_stdin().is_some(),
+            Stdio::Stdout => terminal_stdout::get_terminal_stdout().is_some(),
+            Stdio::Stderr => terminal_stderr::get_terminal_stderr().is_some(),
+        };
+        if is_terminal {
+            wasi::FILETYPE_CHARACTER_DEVICE
+        } else {
+            wasi::FILETYPE_UNKNOWN
         }
     }
 }
@@ -138,19 +145,6 @@ impl Descriptors {
             preopens: Cell::new(None),
         };
 
-        let stdin_isatty = match terminal_stdin::get_terminal_stdin() {
-            Some(_) => IsATTY::Yes,
-            None => IsATTY::No,
-        };
-        let stdout_isatty = match terminal_stdout::get_terminal_stdout() {
-            Some(_) => IsATTY::Yes,
-            None => IsATTY::No,
-        };
-        let stderr_isatty = match terminal_stderr::get_terminal_stderr() {
-            Some(_) => IsATTY::Yes,
-            None => IsATTY::No,
-        };
-
         fn new_once<T>(val: T) -> OnceCell<T> {
             let cell = OnceCell::new();
             let _ = cell.set(val);
@@ -160,19 +154,19 @@ impl Descriptors {
         d.push(Descriptor::Streams(Streams {
             input: new_once(stdin::get_stdin()),
             output: OnceCell::new(),
-            type_: StreamType::Stdio(stdin_isatty),
+            type_: StreamType::Stdio(Stdio::Stdin),
         }))
         .trapping_unwrap();
         d.push(Descriptor::Streams(Streams {
             input: OnceCell::new(),
             output: new_once(stdout::get_stdout()),
-            type_: StreamType::Stdio(stdout_isatty),
+            type_: StreamType::Stdio(Stdio::Stdout),
         }))
         .trapping_unwrap();
         d.push(Descriptor::Streams(Streams {
             input: OnceCell::new(),
             output: new_once(stderr::get_stderr()),
-            type_: StreamType::Stdio(stderr_isatty),
+            type_: StreamType::Stdio(Stdio::Stderr),
         }))
         .trapping_unwrap();
 

diff --git a/crates/wasi-preview1-component-adapter/src/lib.rs b/crates/wasi-preview1-component-adapter/src/lib.rs
@@ -568,7 +568,7 @@ pub unsafe extern "C" fn fd_fdstat_get(fd: Fd, stat: *mut Fdstat) -> Errno {
             Descriptor::Streams(Streams {
                 input,
                 output,
-                type_: StreamType::Stdio(isatty),
+                type_: StreamType::Stdio(stdio),
             }) => {
                 let fs_flags = 0;
                 let mut fs_rights_base = 0;
@@ -580,7 +580,7 @@ pub unsafe extern "C" fn fd_fdstat_get(fd: Fd, stat: *mut Fdstat) -> Errno {
                 }
                 let fs_rights_inheriting = fs_rights_base;
                 stat.write(Fdstat {
-                    fs_filetype: isatty.filetype(),
+                    fs_filetype: stdio.filetype(),
                     fs_flags,
                     fs_rights_base,
                     fs_rights_inheriting,
@@ -663,13 +663,13 @@ pub unsafe extern "C" fn fd_filestat_get(fd: Fd, buf: *mut Filestat) -> Errno {
             }
             // Stdio is all zero fields, except for filetype character device
             Descriptor::Streams(Streams {
-                type_: StreamType::Stdio(isatty),
+                type_: StreamType::Stdio(stdio),
                 ..
             }) => {
                 *buf = Filestat {
                     dev: 0,
                     ino: 0,
-                    filetype: isatty.filetype(),
+                    filetype: stdio.filetype(),
                     nlink: 0,
                     size: 0,
                     atim: 0,