Add `-o` flag for `export` command (#1035)

* Add `-o` flag for `export` command

The export command now prints to standard output by default.  To store the
output in a file, the new `-o <filename>` argument can be used.

* Fix code style

* Improve usage examples for `export` command

* Add missing import statement to exporter module

* Make Exporter class work w/ IO objects for output

* Fix test suite for `Exporter` utility class

README.md

@@ -546,6 +546,21 @@ This command locks (without installing) the dependencies specified in `pyproject
 poetry lock
 poetry lock
 ```
 ```
 
 
+### export
+
+This command exports the lock file to other formats.
+
+```bash
+poetry export -f requirements.txt > requirements.txt
+```
+
+#### Options
+
+* `--format (-f)`: the format to export to.  Currently, only
+  `requirements.txt` is supported.
+* `--output (-o)`: the name of the output file.  If omitted, print to standard
+  output.
+
 
 
 ## The `pyproject.toml` file
 ## The `pyproject.toml` file
 
 

docs/docs/cli.md

@@ -427,16 +427,21 @@ The new version should ideally be a valid semver string or a valid bump rule:
 
 
 This command exports the lock file to other formats.
 This command exports the lock file to other formats.
 
 
-If the lock file does not exist, it will be created automatically.
-
 ```bash
 ```bash
-poetry export -f requirements.txt
+poetry export -f requirements.txt > requirements.txt
 ```
 ```
 
 
 !!!note
 !!!note
 
 
     Only the `requirements.txt` format is currently supported.
     Only the `requirements.txt` format is currently supported.
 
 
+### Options
+
+* `--format (-f)`: the format to export to.  Currently, only
+  `requirements.txt` is supported.
+* `--output (-o)`: the name of the output file.  If omitted, print to standard
+  output.
+
 ## env
 ## env
 
 
 The `env` command regroups sub commands to interact with the virtualenvs
 The `env` command regroups sub commands to interact with the virtualenvs

poetry/console/commands/export.py

@@ -11,6 +11,7 @@ class ExportCommand(Command):
 
 
     options = [
     options = [
         option("format", "f", "Format to export to.", flag=False),
         option("format", "f", "Format to export to.", flag=False),
+        option("output", "o", "The name of the output file.", flag=False),
         option("without-hashes", None, "Exclude hashes from the exported file."),
         option("without-hashes", None, "Exclude hashes from the exported file."),
         option("dev", None, "Include development dependencies."),
         option("dev", None, "Include development dependencies."),
     ]
     ]
@@ -21,6 +22,8 @@ class ExportCommand(Command):
         if fmt not in Exporter.ACCEPTED_FORMATS:
         if fmt not in Exporter.ACCEPTED_FORMATS:
             raise ValueError("Invalid export format: {}".format(fmt))
             raise ValueError("Invalid export format: {}".format(fmt))
 
 
+        output = self.option("output")
+
         locker = self.poetry.locker
         locker = self.poetry.locker
         if not locker.is_locked():
         if not locker.is_locked():
             self.line("<comment>The lock file does not exist. Locking.</comment>")
             self.line("<comment>The lock file does not exist. Locking.</comment>")
@@ -48,6 +51,7 @@ class ExportCommand(Command):
         exporter.export(
         exporter.export(
             fmt,
             fmt,
             self.poetry.file.parent,
             self.poetry.file.parent,
+            output or self.io,
             with_hashes=not self.option("without-hashes"),
             with_hashes=not self.option("without-hashes"),
             dev=self.option("dev"),
             dev=self.option("dev"),
         )
         )

poetry/utils/exporter.py

+from typing import Optional
+
+from clikit.api.io import IO
+
 from poetry.packages.locker import Locker
 from poetry.packages.locker import Locker
 from poetry.utils._compat import Path
 from poetry.utils._compat import Path
 from poetry.utils._compat import decode
 from poetry.utils._compat import decode
@@ -14,19 +18,18 @@ class Exporter(object):
         self._lock = lock
         self._lock = lock
 
 
     def export(
     def export(
-        self, fmt, cwd, with_hashes=True, dev=False
-    ):  # type: (str, Path, bool, bool) -> None
+        self, fmt, cwd, output, with_hashes=True, dev=False
+    ):  # type: (str, Path, Union[IO, str], bool, bool) -> None
         if fmt not in self.ACCEPTED_FORMATS:
         if fmt not in self.ACCEPTED_FORMATS:
             raise ValueError("Invalid export format: {}".format(fmt))
             raise ValueError("Invalid export format: {}".format(fmt))
 
 
         getattr(self, "_export_{}".format(fmt.replace(".", "_")))(
         getattr(self, "_export_{}".format(fmt.replace(".", "_")))(
-            cwd, with_hashes=with_hashes, dev=dev
+            cwd, output, with_hashes=with_hashes, dev=dev
         )
         )
 
 
     def _export_requirements_txt(
     def _export_requirements_txt(
-        self, cwd, with_hashes=True, dev=False
-    ):  # type: (Path, bool, bool) -> None
-        filepath = cwd / "requirements.txt"
+        self, cwd, output, with_hashes=True, dev=False
+    ):  # type: (Path, Union[IO, str], bool, bool) -> None
         content = ""
         content = ""
 
 
         for package in sorted(
         for package in sorted(
@@ -59,5 +62,15 @@ class Exporter(object):
             line += "\n"
             line += "\n"
             content += line
             content += line
 
 
-        with filepath.open("w", encoding="utf-8") as f:
-            f.write(decode(content))
+        self._output(content, cwd, output)
+
+    def _output(
+        self, content, cwd, output
+    ):  # type: (str, Path, Union[IO, str]) -> None
+        decoded = decode(content)
+        try:
+            output.write(decoded)
+        except AttributeError:
+            filepath = cwd / output
+            with filepath.open("w", encoding="utf-8") as f:
+                f.write(decoded)

tests/console/commands/test_export.py

@@ -69,7 +69,7 @@ def test_export_exports_requirements_txt_file_locks_if_no_lock_file(app, repo):
 
 
     repo.add_package(get_package("foo", "1.0.0"))
     repo.add_package(get_package("foo", "1.0.0"))
 
 
-    tester.execute("--format requirements.txt")
+    tester.execute("--format requirements.txt --output requirements.txt")
 
 
     requirements = app.poetry.file.parent / "requirements.txt"
     requirements = app.poetry.file.parent / "requirements.txt"
     assert requirements.exists()
     assert requirements.exists()
@@ -99,7 +99,7 @@ def test_export_exports_requirements_txt_uses_lock_file(app, repo):
     command = app.find("export")
     command = app.find("export")
     tester = CommandTester(command)
     tester = CommandTester(command)
 
 
-    tester.execute("--format requirements.txt")
+    tester.execute("--format requirements.txt --output requirements.txt")
 
 
     requirements = app.poetry.file.parent / "requirements.txt"
     requirements = app.poetry.file.parent / "requirements.txt"
     assert requirements.exists()
     assert requirements.exists()
@@ -131,3 +131,24 @@ def test_export_fails_on_invalid_format(app, repo):
 
 
     with pytest.raises(ValueError):
     with pytest.raises(ValueError):
         tester.execute("--format invalid")
         tester.execute("--format invalid")
+
+
+def test_export_prints_to_stdout_by_default(app, repo):
+    repo.add_package(get_package("foo", "1.0.0"))
+
+    command = app.find("lock")
+    tester = CommandTester(command)
+    tester.execute()
+
+    assert app.poetry.locker.lock.exists()
+
+    command = app.find("export")
+    tester = CommandTester(command)
+
+    tester.execute("--format requirements.txt")
+
+    expected = """\
+foo==1.0.0
+"""
+
+    assert expected == tester.io.fetch_output()

tests/utils/test_exporter.py

+import sys
+
 import pytest
 import pytest
 
 
 from poetry.packages import Locker as BaseLocker
 from poetry.packages import Locker as BaseLocker
@@ -61,7 +63,7 @@ def test_exporter_can_export_requirements_txt_with_standard_packages(tmp_dir, lo
     )
     )
     exporter = Exporter(locker)
     exporter = Exporter(locker)
 
 
-    exporter.export("requirements.txt", Path(tmp_dir))
+    exporter.export("requirements.txt", Path(tmp_dir), "requirements.txt")
 
 
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
         content = f.read()
         content = f.read()
@@ -104,7 +106,7 @@ def test_exporter_can_export_requirements_txt_with_standard_packages_and_hashes(
     )
     )
     exporter = Exporter(locker)
     exporter = Exporter(locker)
 
 
-    exporter.export("requirements.txt", Path(tmp_dir))
+    exporter.export("requirements.txt", Path(tmp_dir), "requirements.txt")
 
 
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
         content = f.read()
         content = f.read()
@@ -149,7 +151,9 @@ def test_exporter_can_export_requirements_txt_with_standard_packages_and_hashes_
     )
     )
     exporter = Exporter(locker)
     exporter = Exporter(locker)
 
 
-    exporter.export("requirements.txt", Path(tmp_dir), with_hashes=False)
+    exporter.export(
+        "requirements.txt", Path(tmp_dir), "requirements.txt", with_hashes=False
+    )
 
 
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
         content = f.read()
         content = f.read()
@@ -192,7 +196,7 @@ def test_exporter_exports_requirements_txt_without_dev_packages_by_default(
     )
     )
     exporter = Exporter(locker)
     exporter = Exporter(locker)
 
 
-    exporter.export("requirements.txt", Path(tmp_dir))
+    exporter.export("requirements.txt", Path(tmp_dir), "requirements.txt")
 
 
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
         content = f.read()
         content = f.read()
@@ -235,7 +239,7 @@ def test_exporter_exports_requirements_txt_with_dev_packages_if_opted_in(
     )
     )
     exporter = Exporter(locker)
     exporter = Exporter(locker)
 
 
-    exporter.export("requirements.txt", Path(tmp_dir), dev=True)
+    exporter.export("requirements.txt", Path(tmp_dir), "requirements.txt", dev=True)
 
 
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
         content = f.read()
         content = f.read()
@@ -276,7 +280,7 @@ def test_exporter_can_export_requirements_txt_with_git_packages(tmp_dir, locker)
     )
     )
     exporter = Exporter(locker)
     exporter = Exporter(locker)
 
 
-    exporter.export("requirements.txt", Path(tmp_dir))
+    exporter.export("requirements.txt", Path(tmp_dir), "requirements.txt")
 
 
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
         content = f.read()
         content = f.read()
@@ -310,7 +314,7 @@ def test_exporter_can_export_requirements_txt_with_directory_packages(tmp_dir, l
     )
     )
     exporter = Exporter(locker)
     exporter = Exporter(locker)
 
 
-    exporter.export("requirements.txt", Path(tmp_dir))
+    exporter.export("requirements.txt", Path(tmp_dir), "requirements.txt")
 
 
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
         content = f.read()
         content = f.read()
@@ -344,7 +348,7 @@ def test_exporter_can_export_requirements_txt_with_file_packages(tmp_dir, locker
     )
     )
     exporter = Exporter(locker)
     exporter = Exporter(locker)
 
 
-    exporter.export("requirements.txt", Path(tmp_dir))
+    exporter.export("requirements.txt", Path(tmp_dir), "requirements.txt")
 
 
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
         content = f.read()
         content = f.read()
@@ -389,7 +393,7 @@ def test_exporter_exports_requirements_txt_with_legacy_packages(tmp_dir, locker)
     )
     )
     exporter = Exporter(locker)
     exporter = Exporter(locker)
 
 
-    exporter.export("requirements.txt", Path(tmp_dir), dev=True)
+    exporter.export("requirements.txt", Path(tmp_dir), "requirements.txt", dev=True)
 
 
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
     with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
         content = f.read()
         content = f.read()
@@ -403,3 +407,42 @@ foo==1.2.3 \\
 """
 """
 
 
     assert expected == content
     assert expected == content
+
+
+def test_exporter_exports_requirements_txt_to_standard_output(tmp_dir, locker, capsys):
+    locker.mock_lock_data(
+        {
+            "package": [
+                {
+                    "name": "foo",
+                    "version": "1.2.3",
+                    "category": "main",
+                    "optional": False,
+                    "python-versions": "*",
+                },
+                {
+                    "name": "bar",
+                    "version": "4.5.6",
+                    "category": "main",
+                    "optional": False,
+                    "python-versions": "*",
+                },
+            ],
+            "metadata": {
+                "python-versions": "*",
+                "content-hash": "123456789",
+                "hashes": {"foo": [], "bar": []},
+            },
+        }
+    )
+    exporter = Exporter(locker)
+
+    exporter.export("requirements.txt", Path(tmp_dir), sys.stdout)
+
+    out, err = capsys.readouterr()
+    expected = """\
+bar==4.5.6
+foo==1.2.3
+"""
+
+    assert out == expected