fix: piped input on macOS and extension-less paths like <(cmd) (#30)

.github/workflows/ci.yml

@@ -21,6 +21,17 @@ jobs:
       - uses: dtolnay/rust-toolchain@stable
       - uses: Swatinem/rust-cache@v2
       - run: cargo test
+      # cargo test never opens a terminal, so it cannot see #30: with stdin piped,
+      # crossterm reads keys from /dev/tty, and on macOS that failed at startup.
+      # `script` provides the pty; the data comes down the pipe, `q` through the tty.
+      - name: Piped stdin smoke test
+        if: runner.os == 'macOS'
+        timeout-minutes: 2
+        run: |
+          cargo build
+          (sleep 5; printf q) | script -q /dev/null sh -c \
+            'stty rows 40 cols 120; cat tests/fixtures/orders.json | target/debug/datasight; echo $? > rc'
+          test "$(cat rc)" = 0
 
   clippy:
     name: Clippy

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 All notable changes to this project will be documented in this file.
 
+## [Unreleased]
+
+### Fixed
+- Piping data into datasight works on macOS (#30). Any piped input — `cat data.csv | datasight`, an HTTP response, anything — died at startup with `Failed to initialize input reader`: with stdin taken by the pipe, keys are read from `/dev/tty`, and the default event source waits on it through kqueue, which macOS does not support for terminals. crossterm's `use-dev-tty` feature reads the tty with a source that works there. CI now runs a piped-stdin smoke test on macOS inside a pty, since `cargo test` never opens a terminal and could not catch this.
+- `datasight <(cmd)` loads the data instead of failing with `Unsupported file format: .` A path without an extension (process substitution hands over `/dev/fd/N`) is now identified from its content, the same way stdin is: `[` is JSON, `{` is NDJSON, anything else is CSV.
+
 ## [0.10.0] - 2026-08-23
 
 ### Added

Cargo.toml

@@ -15,7 +15,7 @@ azure = ["dep:object_store", "object_store/azure", "dep:tokio"]
 aws   = ["dep:object_store", "object_store/aws",   "dep:tokio"]
 
 [dependencies]
-crossterm = { version = "0.29.0", features = ["osc52"] }
+crossterm = { version = "0.29.0", features = ["osc52", "use-dev-tty"] }
 ratatui = "0.30.0"
 polars = { version = "0.46", features = ["csv", "parquet", "lazy", "strings", "regex", "json", "temporal", "dtype-date", "dtype-datetime", "dtype-decimal", "dtype-duration", "dtype-time"] }
 clap = { version = "4", features = ["derive"] }

qa.sh

@@ -255,6 +255,11 @@ launch "cat tests/fixtures/orders.json | $BINARY"
 assert_contains "A/stdin-json" "order_id"
 quit
 
+# process substitution: the path is /dev/fd/N, no extension to dispatch on (#30)
+launch "$BINARY <(cat tests/fixtures/orders.json)"
+assert_contains "A/procsub-json" "order_id"
+quit
+
 # ── Suite B: Normal mode navigation ───────────────────────────────────────────
 echo ""
 echo "=== Suite B: Normal mode navigation ==="

src/main.rs

@@ -116,6 +116,9 @@ pub(crate) fn load_dataframe(
             .with_json_format(JsonFormat::Json)
             .finish()?,
         "ndjson" | "jsonl" => JsonLineReader::new(std::fs::File::open(file_path)?).finish()?,
+        // No extension to go on — e.g. `<(cmd)` hands us /dev/fd/63, a pipe that can
+        // only be read once — so sniff the content the same way stdin does.
+        "" => return parse_buf(std::fs::read(file_path)?, delimiter),
         _ => {
             if let Some(sep) = delimiter {
                 csv_options(sep)
@@ -547,6 +550,17 @@ mod tests {
         assert!(load_dataframe("tests/fixtures/orders.csv.bak", None).is_err());
     }
 
+    #[test]
+    fn test_no_extension_sniffs_content() {
+        // Stands in for `datasight <(cmd)`, whose /dev/fd/N path has no extension (#30).
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("orders");
+        std::fs::copy("tests/fixtures/orders.json", &path).unwrap();
+        let df = load_dataframe(path.to_str().unwrap(), None).expect("should sniff as JSON");
+        let expected = load_dataframe("tests/fixtures/orders.json", None).unwrap();
+        assert!(df.equals_missing(&expected));
+    }
+
     #[test]
     fn test_try_parse_date_columns_mm_dd_yyyy() {
         // Non-ISO date strings like "12/25/2022" are sorted lexicographically