command/add: introduce --editable option

This change allows for vcs/path dependencies to be installed with
`develop=true` configured.

docs/docs/cli.md

@@ -272,7 +272,14 @@ poetry add ../my-package/dist/my-package-0.1.0.tar.gz
 poetry add ../my-package/dist/my_package-0.1.0.whl
 ```
 
-If you want the dependency to be installed in editable mode you can specify it in the `pyproject.toml` file. It means that changes in the local directory will be reflected directly in environment.
+If you want the dependency to be installed in editable mode you can use the `--editable` option.
+
+```bash
+poetry add --editable ./my-package/
+poetry add --editable git+ssh://github.com/sdispater/pendulum.git#develop
+```
+
+Alternatively, you can specify it in the `pyproject.toml` file. It means that changes in the local directory will be reflected directly in environment.
 
 ```toml
 [tool.poetry.dependencies]
@@ -296,6 +303,7 @@ poetry add "git+https://github.com/pallets/flask.git@1.1.1[dotenv,dev]"
 ### Options
 
 * `--dev (-D)`: Add package as development dependency.
+* `--editable (-e)`: Add vcs/path dependencies as editable.
 * `--extras (-E)`: Extras to activate for the dependency. (multiple values allowed)
 * `--optional`: Add as an optional dependency.
 * `--python`: Python version for which the dependency must be installed.

poetry/console/commands/add.py

@@ -17,6 +17,7 @@ class AddCommand(InstallerCommand, InitCommand):
     arguments = [argument("name", "The packages to add.", multiple=True)]
     options = [
         option("dev", "D", "Add as a development dependency."),
+        option("editable", "e", "Add vcs/path dependencies as editable."),
         option(
             "extras",
             "E",
@@ -139,6 +140,19 @@ class AddCommand(InstallerCommand, InitCommand):
 
                 constraint["extras"] = self.option("extras")
 
+            if self.option("editable"):
+                if "git" in _constraint or "path" in _constraint:
+                    constraint["develop"] = True
+                else:
+                    self.line_error(
+                        "\n"
+                        "<error>Failed to add packages. "
+                        "Only vcs/path dependencies support editable installs. "
+                        f"<c1>{_constraint['name']}</c1> is neither."
+                    )
+                    self.line_error("\nNo changes were applied.")
+                    return 1
+
             if self.option("python"):
                 constraint["python"] = self.option("python")
 

tests/console/commands/test_add.py

@@ -50,6 +50,24 @@ Package operations: 1 install, 0 updates, 0 removals
     assert content["dependencies"]["cachy"] == "^0.2.0"
 
 
+def test_add_no_constraint_editable_error(app, repo, tester):
+    content = app.poetry.file.read()["tool"]["poetry"]
+
+    repo.add_package(get_package("cachy", "0.2.0"))
+
+    tester.execute("-e cachy")
+
+    expected = """
+Failed to add packages. Only vcs/path dependencies support editable installs. cachy is neither.
+
+No changes were applied.
+"""
+    assert 1 == tester.status_code
+    assert expected == tester.io.fetch_error()
+    assert 0 == tester.command.installer.executor.installations_count
+    assert content == app.poetry.file.read()["tool"]["poetry"]
+
+
 def test_add_equal_constraint(app, repo, tester):
     repo.add_package(get_package("cachy", "0.1.0"))
     repo.add_package(get_package("cachy", "0.2.0"))
@@ -243,13 +261,15 @@ Package operations: 4 installs, 0 updates, 0 removals
     }
 
 
-def test_add_git_ssh_constraint(app, repo, tester, tmp_venv):
+@pytest.mark.parametrize("editable", [False, True])
+def test_add_git_ssh_constraint(editable, app, repo, tester, tmp_venv):
     tester.command.set_env(tmp_venv)
 
     repo.add_package(get_package("pendulum", "1.4.4"))
     repo.add_package(get_package("cleo", "0.6.5"))
 
-    tester.execute("git+ssh://git@github.com/demo/demo.git@develop")
+    url = "git+ssh://git@github.com/demo/demo.git@develop"
+    tester.execute(f"{url}" if not editable else f"-e {url}")
 
     expected = """\
 
@@ -270,13 +290,19 @@ Package operations: 2 installs, 0 updates, 0 removals
     content = app.poetry.file.read()["tool"]["poetry"]
 
     assert "demo" in content["dependencies"]
-    assert content["dependencies"]["demo"] == {
+
+    expected = {
         "git": "ssh://git@github.com/demo/demo.git",
         "rev": "develop",
     }
+    if editable:
+        expected["develop"] = True
+
+    assert content["dependencies"]["demo"] == expected
 
 
-def test_add_directory_constraint(app, repo, tester, mocker):
+@pytest.mark.parametrize("editable", [False, True])
+def test_add_directory_constraint(editable, app, repo, tester, mocker):
     p = mocker.patch("pathlib.Path.cwd")
     p.return_value = Path(__file__).parent
 
@@ -284,7 +310,7 @@ def test_add_directory_constraint(app, repo, tester, mocker):
     repo.add_package(get_package("cleo", "0.6.5"))
 
     path = "../git/github.com/demo/demo"
-    tester.execute("{}".format(path))
+    tester.execute(f"{path}" if not editable else f"-e {path}")
 
     expected = """\
 
@@ -307,7 +333,12 @@ Package operations: 2 installs, 0 updates, 0 removals
     content = app.poetry.file.read()["tool"]["poetry"]
 
     assert "demo" in content["dependencies"]
-    assert content["dependencies"]["demo"] == {"path": "../git/github.com/demo/demo"}
+
+    expected = {"path": "../git/github.com/demo/demo"}
+    if editable:
+        expected["develop"] = True
+
+    assert content["dependencies"]["demo"] == expected
 
 
 def test_add_directory_with_poetry(app, repo, tester, mocker):