Add show-config command to print resolved configuration

crates/karva/Cargo.toml

@@ -36,6 +36,7 @@ clap = { workspace = true, features = ["wrap_help", "string", "env"] }
 colored = { workspace = true }
 crossbeam-channel = { workspace = true }
 notify-debouncer-mini = { workspace = true }
+toml = { workspace = true }
 tracing = { workspace = true, features = ["release_max_level_debug"] }
 wild = { workspace = true }
 

crates/karva/src/commands/mod.rs

@@ -1,4 +1,5 @@
 pub mod cache;
+pub mod show_config;
 pub mod snapshot;
 pub mod test;
 pub mod version;

crates/karva/src/commands/show_config.rs

@@ -0,0 +1,46 @@
+use std::fmt::Write;
+
+use anyhow::{Context as _, Result};
+use karva_cli::ShowConfigCommand;
+use karva_logging::Printer;
+use karva_metadata::{Options, ProjectMetadata, ProjectOptionsOverrides};
+use karva_project::Project;
+use karva_project::path::absolute;
+use karva_python_semantic::current_python_version;
+
+use crate::ExitStatus;
+use crate::utils::cwd;
+
+pub fn show_config(args: ShowConfigCommand) -> Result<ExitStatus> {
+    let cwd = cwd().map_err(|_| {
+        anyhow::anyhow!(
+            "The current working directory contains non-Unicode characters. karva only supports Unicode paths."
+        )
+    })?;
+
+    let python_version = current_python_version();
+
+    let config_file = args.config_file.as_ref().map(|path| absolute(path, &cwd));
+
+    let mut project_metadata = if let Some(config_file) = &config_file {
+        ProjectMetadata::from_config_file(config_file.clone(), &cwd, python_version)?
+    } else {
+        ProjectMetadata::discover(&cwd, python_version)?
+    };
+
+    let overrides =
+        ProjectOptionsOverrides::new(config_file, Options::default()).with_profile(args.profile);
+    project_metadata
+        .apply_overrides(&overrides)
+        .map_err(|err| anyhow::anyhow!("{err}"))?;
+
+    let project = Project::from_metadata(project_metadata);
+
+    let serialized =
+        toml::to_string(project.settings()).context("failed to serialize configuration")?;
+
+    let mut stdout = Printer::default().stream_for_message().lock();
+    write!(stdout, "{serialized}")?;
+
+    Ok(ExitStatus::Success)
+}

crates/karva/src/lib.rs

@@ -45,6 +45,9 @@ fn run(f: impl FnOnce(Vec<OsString>) -> Vec<OsString>) -> anyhow::Result<ExitSta
         Command::Test(test_args) => commands::test::test(*test_args),
         Command::Snapshot(snapshot_args) => commands::snapshot::snapshot(snapshot_args),
         Command::Cache(cache_args) => commands::cache::cache(&cache_args),
+        Command::ShowConfig(show_config_args) => {
+            commands::show_config::show_config(show_config_args)
+        }
         Command::Version => commands::version::version().map(|()| ExitStatus::Success),
     }
 }

crates/karva/tests/it/basic.rs

@@ -2653,11 +2653,12 @@ fn test_no_subcommand_prints_help() {
     Usage: karva <COMMAND>
 
     Commands:
-      test      Run tests
-      snapshot  Manage snapshots created by `karva.assert_snapshot()`
-      cache     Manage the karva cache
-      version   Display Karva's version
-      help      Print this message or the help of the given subcommand(s)
+      test         Run tests
+      snapshot     Manage snapshots created by `karva.assert_snapshot()`
+      cache        Manage the karva cache
+      show-config  Print the resolved configuration karva would run with
+      version      Display Karva's version
+      help         Print this message or the help of the given subcommand(s)
 
     Options:
       -h, --help     Print help

crates/karva/tests/it/common/mod.rs

@@ -187,6 +187,12 @@ impl TestContext {
         command.arg("version").current_dir(self.root());
         command
     }
+
+    pub fn show_config(&self) -> Command {
+        let mut command = self.karva_command();
+        command.arg("show-config").current_dir(self.root());
+        command
+    }
 }
 
 impl Default for TestContext {

crates/karva/tests/it/main.rs

@@ -12,5 +12,6 @@ mod filterset;
 mod last_failed;
 mod partition;
 mod run_ignored;
+mod show_config;
 mod version;
 mod watch;

crates/karva/tests/it/show_config.rs

@@ -0,0 +1,190 @@
+use insta_cmd::assert_cmd_snapshot;
+
+use crate::common::TestContext;
+
+#[test]
+fn show_config_default_profile() {
+    let context = TestContext::default();
+
+    assert_cmd_snapshot!(context.show_config(), @r#"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    [src]
+    respect-ignore-files = true
+    include = []
+
+    [terminal]
+    output-format = "full"
+    show-python-output = false
+    status-level = "pass"
+    final-status-level = "pass"
+
+    [test]
+    test-function-prefix = "test"
+    try-import-fixtures = false
+    retry = 0
+    no-tests = "auto"
+
+    [coverage]
+    sources = []
+    report = "term"
+
+    ----- stderr -----
+    "#);
+}
+
+#[test]
+fn show_config_resolves_pyproject_options() {
+    let context = TestContext::with_file(
+        "pyproject.toml",
+        r#"
+[tool.karva.profile.default.test]
+test-function-prefix = "check"
+fail-fast = true
+
+[tool.karva.profile.default.terminal]
+output-format = "concise"
+"#,
+    );
+
+    assert_cmd_snapshot!(context.show_config(), @r#"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    [src]
+    respect-ignore-files = true
+    include = []
+
+    [terminal]
+    output-format = "concise"
+    show-python-output = false
+    status-level = "pass"
+    final-status-level = "pass"
+
+    [test]
+    test-function-prefix = "check"
+    max-fail = 1
+    try-import-fixtures = false
+    retry = 0
+    no-tests = "auto"
+
+    [coverage]
+    sources = []
+    report = "term"
+
+    ----- stderr -----
+    "#);
+}
+
+#[test]
+fn show_config_named_profile_layers_over_default() {
+    let context = TestContext::with_file(
+        "karva.toml",
+        r#"
+[profile.default.test]
+test-function-prefix = "check"
+
+[profile.ci.test]
+retry = 3
+
+[profile.ci.terminal]
+output-format = "concise"
+"#,
+    );
+
+    assert_cmd_snapshot!(context.show_config().args(["--profile", "ci"]), @r#"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    [src]
+    respect-ignore-files = true
+    include = []
+
+    [terminal]
+    output-format = "concise"
+    show-python-output = false
+    status-level = "pass"
+    final-status-level = "pass"
+
+    [test]
+    test-function-prefix = "check"
+    try-import-fixtures = false
+    retry = 3
+    no-tests = "auto"
+
+    [coverage]
+    sources = []
+    report = "term"
+
+    ----- stderr -----
+    "#);
+}
+
+#[test]
+fn show_config_emits_set_timeouts_and_coverage() {
+    let context = TestContext::with_file(
+        "karva.toml",
+        r#"
+[profile.default.test]
+slow-timeout = 0.5
+timeout = 120
+
+[profile.default.coverage]
+sources = ["src"]
+report = "term-missing"
+fail-under = 90
+"#,
+    );
+
+    assert_cmd_snapshot!(context.show_config(), @r#"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    [src]
+    respect-ignore-files = true
+    include = []
+
+    [terminal]
+    output-format = "full"
+    show-python-output = false
+    status-level = "pass"
+    final-status-level = "pass"
+
+    [test]
+    test-function-prefix = "test"
+    try-import-fixtures = false
+    retry = 0
+    no-tests = "auto"
+    slow-timeout = 0.5
+    timeout = 120.0
+
+    [coverage]
+    sources = ["src"]
+    report = "term-missing"
+    fail-under = 90.0
+
+    ----- stderr -----
+    "#);
+}
+
+#[test]
+fn show_config_unknown_profile_errors() {
+    let context = TestContext::with_file(
+        "karva.toml",
+        r"
+[profile.ci.test]
+retry = 3
+",
+    );
+
+    assert_cmd_snapshot!(context.show_config().args(["--profile", "bogus"]), @r"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    Karva failed
+      Cause: profile `bogus` is not defined in configuration (available: ci, default)
+    ");
+}

crates/karva_cli/src/lib.rs

@@ -5,13 +5,15 @@ use clap::builder::styling::{AnsiColor, Effects};
 mod cache;
 mod enums;
 mod partition;
+mod show_config;
 mod snapshot;
 mod test;
 mod verbosity;
 
 pub use cache::{CacheAction, CacheCommand};
 pub use enums::{CovReport, NoTests, OutputFormat, RunIgnored};
 pub use partition::PartitionSelection;
+pub use show_config::ShowConfigCommand;
 pub use snapshot::{
     SnapshotAction, SnapshotCommand, SnapshotDeleteArgs, SnapshotFilterArgs, SnapshotPruneArgs,
 };
@@ -44,6 +46,9 @@ pub enum Command {
     /// Manage the karva cache.
     Cache(CacheCommand),
 
+    /// Print the resolved configuration karva would run with.
+    ShowConfig(ShowConfigCommand),
+
     /// Display Karva's version
     Version,
 }

crates/karva_cli/src/show_config.rs

@@ -0,0 +1,31 @@
+use camino::Utf8PathBuf;
+use clap::Parser;
+
+/// Print the resolved configuration karva would run with.
+///
+/// Resolves the same settings the test runner builds — defaults layered with
+/// `karva.toml` / `pyproject.toml` and any selected profile — and prints them
+/// as TOML.
+#[derive(Debug, Parser)]
+pub struct ShowConfigCommand {
+    /// The path to a `karva.toml` file to use for configuration.
+    #[arg(
+        long,
+        env = "KARVA_CONFIG_FILE",
+        value_name = "PATH",
+        help_heading = "Config options"
+    )]
+    pub config_file: Option<Utf8PathBuf>,
+
+    /// Configuration profile to resolve.
+    ///
+    /// Defaults to `default`.
+    #[arg(
+        short = 'P',
+        long,
+        env = "KARVA_PROFILE",
+        value_name = "NAME",
+        help_heading = "Config options"
+    )]
+    pub profile: Option<String>,
+}

crates/karva_metadata/src/max_fail.rs

@@ -48,6 +48,15 @@ impl MaxFail {
         self.0.is_some()
     }
 
+    /// Returns `true` when no failure limit is configured.
+    ///
+    /// `MaxFail::unlimited()` wraps `None`, which serializers like TOML
+    /// cannot represent — this is exposed primarily so `serde`'s
+    /// `skip_serializing_if` can omit the field.
+    pub fn is_unlimited(&self) -> bool {
+        self.0.is_none()
+    }
+
     /// Returns `true` when the configuration would stop after a single failure.
     ///
     /// This is how the legacy `--fail-fast` boolean is surfaced internally.