Infer output type in uv export

crates/uv-cli/src/lib.rs

@@ -3764,8 +3764,11 @@ pub struct ExportArgs {
     /// The format to which `uv.lock` should be exported.
     ///
     /// Supports both `requirements.txt` and `pylock.toml` (PEP 751) output formats.
-    #[arg(long, value_enum, default_value_t = ExportFormat::default())]
-    pub format: ExportFormat,
+    ///
+    /// uv will infer the output format from the file extension of the output file, if
+    /// provided. Otherwise, defaults to `requirements.txt`.
+    #[arg(long, value_enum)]
+    pub format: Option<ExportFormat>,
 
     /// Export the entire workspace.
     ///

crates/uv-requirements/src/sources.rs

@@ -228,3 +228,9 @@ impl std::fmt::Display for RequirementsSource {
         }
     }
 }
+
+/// Returns `true` if a file name matches the `pylock.toml` pattern defined in PEP 751.
+#[allow(clippy::case_sensitive_file_extension_comparisons)]
+pub fn is_pylock_toml(file_name: &str) -> bool {
+    file_name.starts_with("pylock.") && file_name.ends_with(".toml")
+}

crates/uv/src/commands/project/export.rs

@@ -1,10 +1,10 @@
 use std::env;
+use std::ffi::OsStr;
+use std::path::{Path, PathBuf};
 
 use anyhow::{Context, Result};
 use itertools::Itertools;
 use owo_colors::OwoColorize;
-use std::path::{Path, PathBuf};
-use uv_settings::PythonInstallMirrors;
 
 use uv_cache::Cache;
 use uv_configuration::{
@@ -13,8 +13,10 @@ use uv_configuration::{
 };
 use uv_normalize::{DefaultGroups, PackageName};
 use uv_python::{PythonDownloads, PythonPreference, PythonRequest};
+use uv_requirements::is_pylock_toml;
 use uv_resolver::{PylockToml, RequirementsTxtExport};
 use uv_scripts::{Pep723ItemRef, Pep723Script};
+use uv_settings::PythonInstallMirrors;
 use uv_workspace::{DiscoveryOptions, MemberDiscovery, VirtualProject, Workspace, WorkspaceCache};
 
 use crate::commands::pip::loggers::DefaultResolveLogger;
@@ -51,7 +53,7 @@ impl<'lock> From<&'lock ExportTarget> for LockTarget<'lock> {
 #[allow(clippy::fn_params_excessive_bools)]
 pub(crate) async fn export(
     project_dir: &Path,
-    format: ExportFormat,
+    format: Option<ExportFormat>,
     all_packages: bool,
     package: Option<PackageName>,
     prune: Vec<PackageName>,
@@ -252,6 +254,26 @@ pub(crate) async fn export(
     // Write the resolved dependencies to the output channel.
     let mut writer = OutputWriter::new(!quiet || output_file.is_none(), output_file.as_deref());
 
+    // Determine the output format.
+    let format = format.unwrap_or_else(|| {
+        if output_file
+            .as_deref()
+            .and_then(Path::extension)
+            .is_some_and(|ext| ext.eq_ignore_ascii_case("txt"))
+        {
+            ExportFormat::RequirementsTxt
+        } else if output_file
+            .as_deref()
+            .and_then(Path::file_name)
+            .and_then(OsStr::to_str)
+            .is_some_and(is_pylock_toml)
+        {
+            ExportFormat::PylockToml
+        } else {
+            ExportFormat::RequirementsTxt
+        }
+    });
+
     // Generate the export.
     match format {
         ExportFormat::RequirementsTxt => {

crates/uv/src/settings.rs

@@ -1527,7 +1527,7 @@ impl TreeSettings {
 #[allow(clippy::struct_excessive_bools, dead_code)]
 #[derive(Debug, Clone)]
 pub(crate) struct ExportSettings {
-    pub(crate) format: ExportFormat,
+    pub(crate) format: Option<ExportFormat>,
     pub(crate) all_packages: bool,
     pub(crate) package: Option<PackageName>,
     pub(crate) prune: Vec<PackageName>,

crates/uv/tests/it/export.rs

@@ -3923,3 +3923,156 @@ fn pep_751_sdist_url_subdirectory() -> Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn pep_751_infer_output_format() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["anyio==3.7.0"]
+
+        [build-system]
+        requires = ["setuptools>=42"]
+        build-backend = "setuptools.build_meta"
+        "#,
+    )?;
+
+    context.lock().assert().success();
+
+    uv_snapshot!(context.filters(), context.export().arg("-o").arg("requirements.txt"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv export --cache-dir [CACHE_DIR] -o requirements.txt
+    -e .
+    anyio==3.7.0 \
+        --hash=sha256:275d9973793619a5374e1c89a4f4ad3f4b0a5510a2b5b939444bee8f4c4d37ce \
+        --hash=sha256:eddca883c4175f14df8aedce21054bfca3adb70ffe76a9f607aef9d7fa2ea7f0
+        # via project
+    idna==3.6 \
+        --hash=sha256:9ecdbbd083b06798ae1e86adcbfe8ab1479cf864e4ee30fe4e46a003d12491ca \
+        --hash=sha256:c05567e9c24a6b9faaa835c4821bad0590fbb9d5779e7caa6e1cc4978e7eb24f
+        # via anyio
+    sniffio==1.3.1 \
+        --hash=sha256:2f6da418d1f1e0fddd844478f41680e794e6051915791a034ff65e5f100525a2 \
+        --hash=sha256:f4324edc670a0f49750a81b895f35c3adb843cca46f0530f79fc1babb23789dc
+        # via anyio
+
+    ----- stderr -----
+    Resolved 4 packages in [TIME]
+    ");
+
+    uv_snapshot!(context.filters(), context.export().arg("-o").arg("pylock.toml"), @r#"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv export --cache-dir [CACHE_DIR] -o pylock.toml
+    lock-version = "1.0"
+    created-by = "uv"
+    requires-python = ">=3.12"
+
+    [[packages]]
+    name = "anyio"
+    version = "3.7.0"
+    index = "https://pypi.org/simple"
+    sdist = { url = "https://files.pythonhosted.org/packages/c6/b3/fefbf7e78ab3b805dec67d698dc18dd505af7a18a8dd08868c9b4fa736b5/anyio-3.7.0.tar.gz", upload-time = 2023-05-27T11:12:46Z, size = 142737, hashes = { sha256 = "275d9973793619a5374e1c89a4f4ad3f4b0a5510a2b5b939444bee8f4c4d37ce" } }
+    wheels = [{ url = "https://files.pythonhosted.org/packages/68/fe/7ce1926952c8a403b35029e194555558514b365ad77d75125f521a2bec62/anyio-3.7.0-py3-none-any.whl", upload-time = 2023-05-27T11:12:44Z, size = 80873, hashes = { sha256 = "eddca883c4175f14df8aedce21054bfca3adb70ffe76a9f607aef9d7fa2ea7f0" } }]
+
+    [[packages]]
+    name = "idna"
+    version = "3.6"
+    index = "https://pypi.org/simple"
+    sdist = { url = "https://files.pythonhosted.org/packages/bf/3f/ea4b9117521a1e9c50344b909be7886dd00a519552724809bb1f486986c2/idna-3.6.tar.gz", upload-time = 2023-11-25T15:40:54Z, size = 175426, hashes = { sha256 = "9ecdbbd083b06798ae1e86adcbfe8ab1479cf864e4ee30fe4e46a003d12491ca" } }
+    wheels = [{ url = "https://files.pythonhosted.org/packages/c2/e7/a82b05cf63a603df6e68d59ae6a68bf5064484a0718ea5033660af4b54a9/idna-3.6-py3-none-any.whl", upload-time = 2023-11-25T15:40:52Z, size = 61567, hashes = { sha256 = "c05567e9c24a6b9faaa835c4821bad0590fbb9d5779e7caa6e1cc4978e7eb24f" } }]
+
+    [[packages]]
+    name = "project"
+    version = "0.1.0"
+    directory = { path = ".", editable = true }
+
+    [[packages]]
+    name = "sniffio"
+    version = "1.3.1"
+    index = "https://pypi.org/simple"
+    sdist = { url = "https://files.pythonhosted.org/packages/a2/87/a6771e1546d97e7e041b6ae58d80074f81b7d5121207425c964ddf5cfdbd/sniffio-1.3.1.tar.gz", upload-time = 2024-02-25T23:20:04Z, size = 20372, hashes = { sha256 = "f4324edc670a0f49750a81b895f35c3adb843cca46f0530f79fc1babb23789dc" } }
+    wheels = [{ url = "https://files.pythonhosted.org/packages/e9/44/75a9c9421471a6c4805dbf2356f7c181a29c1879239abab1ea2cc8f38b40/sniffio-1.3.1-py3-none-any.whl", upload-time = 2024-02-25T23:20:01Z, size = 10235, hashes = { sha256 = "2f6da418d1f1e0fddd844478f41680e794e6051915791a034ff65e5f100525a2" } }]
+
+    ----- stderr -----
+    Resolved 4 packages in [TIME]
+    "#);
+
+    uv_snapshot!(context.filters(), context.export().arg("-o").arg("pylock.dev.toml"), @r#"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv export --cache-dir [CACHE_DIR] -o pylock.dev.toml
+    lock-version = "1.0"
+    created-by = "uv"
+    requires-python = ">=3.12"
+
+    [[packages]]
+    name = "anyio"
+    version = "3.7.0"
+    index = "https://pypi.org/simple"
+    sdist = { url = "https://files.pythonhosted.org/packages/c6/b3/fefbf7e78ab3b805dec67d698dc18dd505af7a18a8dd08868c9b4fa736b5/anyio-3.7.0.tar.gz", upload-time = 2023-05-27T11:12:46Z, size = 142737, hashes = { sha256 = "275d9973793619a5374e1c89a4f4ad3f4b0a5510a2b5b939444bee8f4c4d37ce" } }
+    wheels = [{ url = "https://files.pythonhosted.org/packages/68/fe/7ce1926952c8a403b35029e194555558514b365ad77d75125f521a2bec62/anyio-3.7.0-py3-none-any.whl", upload-time = 2023-05-27T11:12:44Z, size = 80873, hashes = { sha256 = "eddca883c4175f14df8aedce21054bfca3adb70ffe76a9f607aef9d7fa2ea7f0" } }]
+
+    [[packages]]
+    name = "idna"
+    version = "3.6"
+    index = "https://pypi.org/simple"
+    sdist = { url = "https://files.pythonhosted.org/packages/bf/3f/ea4b9117521a1e9c50344b909be7886dd00a519552724809bb1f486986c2/idna-3.6.tar.gz", upload-time = 2023-11-25T15:40:54Z, size = 175426, hashes = { sha256 = "9ecdbbd083b06798ae1e86adcbfe8ab1479cf864e4ee30fe4e46a003d12491ca" } }
+    wheels = [{ url = "https://files.pythonhosted.org/packages/c2/e7/a82b05cf63a603df6e68d59ae6a68bf5064484a0718ea5033660af4b54a9/idna-3.6-py3-none-any.whl", upload-time = 2023-11-25T15:40:52Z, size = 61567, hashes = { sha256 = "c05567e9c24a6b9faaa835c4821bad0590fbb9d5779e7caa6e1cc4978e7eb24f" } }]
+
+    [[packages]]
+    name = "project"
+    version = "0.1.0"
+    directory = { path = ".", editable = true }
+
+    [[packages]]
+    name = "sniffio"
+    version = "1.3.1"
+    index = "https://pypi.org/simple"
+    sdist = { url = "https://files.pythonhosted.org/packages/a2/87/a6771e1546d97e7e041b6ae58d80074f81b7d5121207425c964ddf5cfdbd/sniffio-1.3.1.tar.gz", upload-time = 2024-02-25T23:20:04Z, size = 20372, hashes = { sha256 = "f4324edc670a0f49750a81b895f35c3adb843cca46f0530f79fc1babb23789dc" } }
+    wheels = [{ url = "https://files.pythonhosted.org/packages/e9/44/75a9c9421471a6c4805dbf2356f7c181a29c1879239abab1ea2cc8f38b40/sniffio-1.3.1-py3-none-any.whl", upload-time = 2024-02-25T23:20:01Z, size = 10235, hashes = { sha256 = "2f6da418d1f1e0fddd844478f41680e794e6051915791a034ff65e5f100525a2" } }]
+
+    ----- stderr -----
+    Resolved 4 packages in [TIME]
+    "#);
+
+    // TODO(charlie): Error on `pyproject.toml`. Right now, it's treated as `requirements.txt`.
+    uv_snapshot!(context.filters(), context.export().arg("-o").arg("pyproject.toml"), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv export --cache-dir [CACHE_DIR] -o pyproject.toml
+    -e .
+    anyio==3.7.0 \
+        --hash=sha256:275d9973793619a5374e1c89a4f4ad3f4b0a5510a2b5b939444bee8f4c4d37ce \
+        --hash=sha256:eddca883c4175f14df8aedce21054bfca3adb70ffe76a9f607aef9d7fa2ea7f0
+        # via project
+    idna==3.6 \
+        --hash=sha256:9ecdbbd083b06798ae1e86adcbfe8ab1479cf864e4ee30fe4e46a003d12491ca \
+        --hash=sha256:c05567e9c24a6b9faaa835c4821bad0590fbb9d5779e7caa6e1cc4978e7eb24f
+        # via anyio
+    sniffio==1.3.1 \
+        --hash=sha256:2f6da418d1f1e0fddd844478f41680e794e6051915791a034ff65e5f100525a2 \
+        --hash=sha256:f4324edc670a0f49750a81b895f35c3adb843cca46f0530f79fc1babb23789dc
+        # via anyio
+
+    ----- stderr -----
+    Resolved 4 packages in [TIME]
+    ");
+
+    Ok(())
+}

docs/reference/cli.md

@@ -2332,7 +2332,8 @@ uv export [OPTIONS]
 
 <p>Supports both <code>requirements.txt</code> and <code>pylock.toml</code> (PEP 751) output formats.</p>
 
-<p>[default: requirements.txt]</p>
+<p>uv will infer the output format from the file extension of the output file, if provided. Otherwise, defaults to <code>requirements.txt</code>.</p>
+
 <p>Possible values:</p>
 
 <ul>