Migrate link-* tests to Python

tests/test_link.py

@@ -0,0 +1,922 @@
+import os
+import sys
+
+import pytest
+
+
+# Python 2.7 on Windows does not have an `os.symlink()` function.
+# PyPy on Windows raises NotImplementedError when `os.symlink()` is called.
+# Older Python 3 versions on Windows require admin rights to create symlinks.
+#
+# In addition, functions like `os.path.realpath()` on Windows Pythons < 3.8
+# do not resolve symlinks and directory junctions correctly,
+# and `shutil.rmtree()` will fail to delete directory junctions.
+#
+# For these reasons, if the tests are running on Windows with Python < 3.8
+# or with PyPy, the entire link test suite must be skipped.
+#
+if (
+    sys.platform[:5] == "win32"
+    and (sys.version_info < (3, 8) or "pypy" in sys.version.lower())
+):
+    reason = "It is impossible to perform link tests on this platform"
+    pytestmark = pytest.mark.skip(reason=reason)
+
+
+def test_link_canonicalization(home, dotfiles, run_dotbot):
+    """Verify links to symlinked destinations are canonical.
+
+    "Canonical", here, means that dotbot does not create symlinks
+    that point to intermediary symlinks.
+    """
+
+    dotfiles.write("f", "apple")
+    dotfiles.write_config([{"link": {"~/.f": {"path": "f"}}}])
+
+    # Point to the config file in a symlinked dotfiles directory.
+    dotfiles_symlink = os.path.join(home, "dotfiles-symlink")
+    os.symlink(dotfiles.directory, dotfiles_symlink)
+    config_file = os.path.join(dotfiles_symlink, os.path.basename(dotfiles.config_filename))
+    run_dotbot("-c", config_file, custom=True)
+
+    expected = os.path.join(dotfiles.directory, "f")
+    actual = os.readlink(os.path.abspath(os.path.expanduser("~/.f")))
+    if sys.platform[:5] == "win32" and actual.startswith("\\\\?\\"):
+        actual = actual[4:]
+    assert expected == actual
+
+
+@pytest.mark.parametrize("dst", ("~/.f", "~/f"))
+@pytest.mark.parametrize("include_force", (True, False))
+def test_link_default_source(root, home, dst, include_force, dotfiles, run_dotbot):
+    """Verify that default sources are calculated correctly.
+
+    This test includes verifying files with and without leading periods,
+    as well as verifying handling of None dict values.
+    """
+
+    dotfiles.write("f", "apple")
+    config = [
+        {
+            "link": {
+                dst: {"force": False} if include_force else None,
+            }
+        }
+    ]
+    dotfiles.write_config(config)
+    run_dotbot()
+
+    with open(os.path.abspath(os.path.expanduser(dst)), "r") as file:
+        assert file.read() == "apple"
+
+
+def test_link_environment_user_expansion_target(home, dotfiles, run_dotbot):
+    """Verify link expands user in target."""
+
+    src = "~/f"
+    target = "~/g"
+    with open(os.path.abspath(os.path.expanduser(src)), "w") as file:
+        file.write("apple")
+    dotfiles.write_config([{"link": {target: src}}])
+    run_dotbot()
+
+    with open(os.path.abspath(os.path.expanduser(target)), "r") as file:
+        assert file.read() == "apple"
+
+
+def test_link_environment_variable_expansion_source(monkeypatch, root, home, dotfiles, run_dotbot):
+    """Verify link expands environment variables in source."""
+
+    monkeypatch.setenv("APPLE", "h")
+    target = "~/.i"
+    src = "$APPLE"
+    dotfiles.write("h", "grape")
+    dotfiles.write_config([{"link": {target: src}}])
+    run_dotbot()
+
+    with open(os.path.abspath(os.path.expanduser(target)), "r") as file:
+        assert file.read() == "grape"
+
+
+def test_link_environment_variable_expansion_source_extended(monkeypatch, root, home, dotfiles, run_dotbot):
+    """Verify link expands environment variables in extended config syntax."""
+
+    monkeypatch.setenv("APPLE", "h")
+    target = "~/.i"
+    src = "$APPLE"
+    dotfiles.write("h", "grape")
+    dotfiles.write_config([{"link": {target: {"path": src, "relink": True}}}])
+    run_dotbot()
+
+    with open(os.path.abspath(os.path.expanduser(target)), "r") as file:
+        assert file.read() == "grape"
+
+
+def test_link_environment_variable_expansion_target(monkeypatch, root, home, dotfiles, run_dotbot):
+    """Verify link expands environment variables in target.
+
+    If the variable doesn't exist, the "variable" must not be replaced.
+    """
+
+    monkeypatch.setenv("ORANGE", ".config")
+    monkeypatch.setenv("BANANA", "g")
+    monkeypatch.delenv("PEAR", raising=False)
+
+    dotfiles.write("f", "apple")
+    dotfiles.write("h", "grape")
+
+    config = [
+        {
+            "link": {
+                "~/${ORANGE}/$BANANA": {
+                    "path": "f",
+                    "create": True,
+                },
+                "~/$PEAR": "h",
+            }
+        }
+    ]
+    dotfiles.write_config(config)
+    run_dotbot()
+
+    with open(os.path.join(home, ".config", "g"), "r") as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, "$PEAR"), "r") as file:
+        assert file.read() == "grape"
+
+
+def test_link_environment_variable_unset(monkeypatch, root, home, dotfiles, run_dotbot):
+    """Verify link leaves unset environment variables."""
+
+    monkeypatch.delenv("ORANGE", raising=False)
+    dotfiles.write("$ORANGE", "apple")
+    dotfiles.write_config([{"link": {"~/f": "$ORANGE"}}])
+    run_dotbot()
+
+    with open(os.path.join(home, "f"), "r") as file:
+        assert file.read() == "apple"
+
+
+def test_link_force_leaves_when_nonexistent(root, home, dotfiles, run_dotbot):
+    """Verify force doesn't erase sources when targets are nonexistent."""
+
+    os.mkdir(os.path.join(home, "dir"))
+    open(os.path.join(home, "file"), "a").close()
+    config = [
+        {
+            "link": {
+                "~/dir": {"path": "dir", "force": True},
+                "~/file": {"path": "file", "force": True},
+            }
+        }
+    ]
+    dotfiles.write_config(config)
+    with pytest.raises(SystemExit):
+        run_dotbot()
+
+    assert os.path.isdir(os.path.join(home, "dir"))
+    assert os.path.isfile(os.path.join(home, "file"))
+
+
+def test_link_force_overwrite_symlink(home, dotfiles, run_dotbot):
+    """Verify force overwrites a symlinked directory."""
+
+    os.mkdir(os.path.join(home, "dir"))
+    dotfiles.write("dir/f")
+    os.symlink(home, os.path.join(home, ".dir"))
+
+    config = [{"link": {"~/.dir": {"path": "dir", "force": True}}}]
+    dotfiles.write_config(config)
+    run_dotbot()
+
+    assert os.path.isfile(os.path.join(home, ".dir", "f"))
+
+
+def test_link_glob_1(home, dotfiles, run_dotbot):
+    """Verify globbing works."""
+
+    dotfiles.write("bin/a", "apple")
+    dotfiles.write("bin/b", "banana")
+    dotfiles.write("bin/c", "cherry")
+    dotfiles.write_config([
+        {"defaults": {"link": {"glob": True, "create": True}}},
+        {"link": {"~/bin": "bin/*"}},
+    ])
+    run_dotbot()
+
+    with open(os.path.join(home, "bin", "a")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, "bin", "b")) as file:
+        assert file.read() == "banana"
+    with open(os.path.join(home, "bin", "c")) as file:
+        assert file.read() == "cherry"
+
+
+def test_link_glob_2(home, dotfiles, run_dotbot):
+    """Verify globbing works with a trailing slash in the source."""
+
+    dotfiles.write("bin/a", "apple")
+    dotfiles.write("bin/b", "banana")
+    dotfiles.write("bin/c", "cherry")
+    dotfiles.write_config([
+        {"defaults": {"link": {"glob": True, "create": True}}},
+        {"link": {"~/bin/": "bin/*"}},
+    ])
+    run_dotbot()
+
+    with open(os.path.join(home, "bin", "a")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, "bin", "b")) as file:
+        assert file.read() == "banana"
+    with open(os.path.join(home, "bin", "c")) as file:
+        assert file.read() == "cherry"
+
+
+def test_link_glob_3(home, dotfiles, run_dotbot):
+    """Verify globbing works with hidden ("period-prefixed") files."""
+
+    dotfiles.write("bin/.a", "dot-apple")
+    dotfiles.write("bin/.b", "dot-banana")
+    dotfiles.write("bin/.c", "dot-cherry")
+    dotfiles.write_config([
+        {"defaults": {"link": {"glob": True, "create": True}}},
+        {"link": {"~/bin/": "bin/.*"}},
+    ])
+    run_dotbot()
+
+    with open(os.path.join(home, "bin", ".a")) as file:
+        assert file.read() == "dot-apple"
+    with open(os.path.join(home, "bin", ".b")) as file:
+        assert file.read() == "dot-banana"
+    with open(os.path.join(home, "bin", ".c")) as file:
+        assert file.read() == "dot-cherry"
+
+
+def test_link_glob_4(home, dotfiles, run_dotbot):
+    """Verify globbing works at the root of the home and dotfiles directories."""
+
+    dotfiles.write(".a", "dot-apple")
+    dotfiles.write(".b", "dot-banana")
+    dotfiles.write(".c", "dot-cherry")
+    dotfiles.write_config([{
+        "link": {
+            "~": {
+                "path": ".*",
+                "glob": True,
+            },
+        },
+    }])
+    run_dotbot()
+
+    with open(os.path.join(home, ".a")) as file:
+        assert file.read() == "dot-apple"
+    with open(os.path.join(home, ".b")) as file:
+        assert file.read() == "dot-banana"
+    with open(os.path.join(home, ".c")) as file:
+        assert file.read() == "dot-cherry"
+
+
+@pytest.mark.parametrize("path", ("foo", "foo/"))
+def test_link_glob_ambiguous_failure(path, home, dotfiles, run_dotbot):
+    """Verify ambiguous link globbing fails."""
+
+    dotfiles.makedirs("foo")
+    dotfiles.write_config([{
+        "link": {
+            "~/foo/": {
+                "path": path,
+                "glob": True,
+            }
+        }
+    }])
+    with pytest.raises(SystemExit):
+        run_dotbot()
+    assert not os.path.exists(os.path.join(home, "foo"))
+
+
+def test_link_glob_ambiguous_success(home, dotfiles, run_dotbot):
+    """Verify the case where ambiguous link globbing succeeds."""
+
+    dotfiles.makedirs("foo")
+    dotfiles.write_config([{
+        "link": {
+            "~/foo": {
+                "path": "foo",
+                "glob": True,
+            }
+        }
+    }])
+    run_dotbot()
+    assert os.path.exists(os.path.join(home, "foo"))
+
+
+def test_link_glob_exclude_1(home, dotfiles, run_dotbot):
+    """Verify link globbing with an explicit exclusion."""
+
+    dotfiles.write("config/foo/a", "apple")
+    dotfiles.write("config/bar/b", "banana")
+    dotfiles.write("config/bar/c", "cherry")
+    dotfiles.write("config/baz/d", "donut")
+    dotfiles.write_config([
+        {
+            "defaults": {
+                "link": {
+                    "glob": True,
+                    "create": True,
+                },
+            },
+        },
+        {
+            "link": {
+                "~/.config/": {
+                    "path": "config/*",
+                    "exclude": ["config/baz"],
+                },
+            },
+        },
+    ])
+    run_dotbot()
+
+    assert not os.path.exists(os.path.join(home, ".config", "baz"))
+
+    assert not os.path.islink(os.path.join(home, ".config"))
+    assert os.path.islink(os.path.join(home, ".config", "foo"))
+    assert os.path.islink(os.path.join(home, ".config", "bar"))
+    with open(os.path.join(home, ".config", "foo", "a")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, ".config", "bar", "b")) as file:
+        assert file.read() == "banana"
+    with open(os.path.join(home, ".config", "bar", "c")) as file:
+        assert file.read() == "cherry"
+
+
+def test_link_glob_exclude_2(home, dotfiles, run_dotbot):
+    """Verify deep link globbing with a globbed exclusion."""
+
+    dotfiles.write("config/foo/a", "apple")
+    dotfiles.write("config/bar/b", "banana")
+    dotfiles.write("config/bar/c", "cherry")
+    dotfiles.write("config/baz/d", "donut")
+    dotfiles.write("config/baz/buzz/e", "egg")
+    dotfiles.write_config([
+        {
+            "defaults": {
+                "link": {
+                    "glob": True,
+                    "create": True,
+                },
+            },
+        },
+        {
+            "link": {
+                "~/.config/": {
+                    "path": "config/*/*",
+                    "exclude": ["config/baz/*"],
+                },
+            },
+        },
+    ])
+    run_dotbot()
+
+    assert not os.path.exists(os.path.join(home, ".config", "baz"))
+
+    assert not os.path.islink(os.path.join(home, ".config"))
+    assert not os.path.islink(os.path.join(home, ".config", "foo"))
+    assert not os.path.islink(os.path.join(home, ".config", "bar"))
+    assert os.path.islink(os.path.join(home, ".config", "foo", "a"))
+    with open(os.path.join(home, ".config", "foo", "a")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, ".config", "bar", "b")) as file:
+        assert file.read() == "banana"
+    with open(os.path.join(home, ".config", "bar", "c")) as file:
+        assert file.read() == "cherry"
+
+
+def test_link_glob_exclude_3(home, dotfiles, run_dotbot):
+    """Verify deep link globbing with an explicit exclusion."""
+
+    dotfiles.write("config/foo/a", "apple")
+    dotfiles.write("config/bar/b", "banana")
+    dotfiles.write("config/bar/c", "cherry")
+    dotfiles.write("config/baz/d", "donut")
+    dotfiles.write("config/baz/buzz/e", "egg")
+    dotfiles.write("config/baz/bizz/g", "grape")
+    dotfiles.write_config([
+        {
+            "defaults": {
+                "link": {
+                    "glob": True,
+                    "create": True,
+                },
+            },
+        },
+        {
+            "link": {
+                "~/.config/": {
+                    "path": "config/*/*",
+                    "exclude": ["config/baz/buzz"],
+                },
+            },
+        },
+    ])
+    run_dotbot()
+
+    assert not os.path.exists(os.path.join(home, ".config", "baz", "buzz"))
+
+    assert not os.path.islink(os.path.join(home, ".config"))
+    assert not os.path.islink(os.path.join(home, ".config", "foo"))
+    assert not os.path.islink(os.path.join(home, ".config", "bar"))
+    assert not os.path.islink(os.path.join(home, ".config", "baz"))
+    assert os.path.islink(os.path.join(home, ".config", "baz", "bizz"))
+    assert os.path.islink(os.path.join(home, ".config", "foo", "a"))
+    with open(os.path.join(home, ".config", "foo", "a")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, ".config", "bar", "b")) as file:
+        assert file.read() == "banana"
+    with open(os.path.join(home, ".config", "bar", "c")) as file:
+        assert file.read() == "cherry"
+    with open(os.path.join(home, ".config", "baz", "d")) as file:
+        assert file.read() == "donut"
+    with open(os.path.join(home, ".config", "baz", "bizz", "g")) as file:
+        assert file.read() == "grape"
+
+
+def test_link_glob_exclude_4(home, dotfiles, run_dotbot):
+    """Verify deep link globbing with multiple globbed exclusions."""
+
+    dotfiles.write("config/foo/a", "apple")
+    dotfiles.write("config/bar/b", "banana")
+    dotfiles.write("config/bar/c", "cherry")
+    dotfiles.write("config/baz/d", "donut")
+    dotfiles.write("config/baz/buzz/e", "egg")
+    dotfiles.write("config/baz/bizz/g", "grape")
+    dotfiles.write("config/fiz/f", "fig")
+    dotfiles.write_config([
+        {
+            "defaults": {
+                "link": {
+                    "glob": True,
+                    "create": True,
+                },
+            },
+        },
+        {
+            "link": {
+                "~/.config/": {
+                    "path": "config/*/*",
+                    "exclude": ["config/baz/*", "config/fiz/*"],
+                },
+            },
+        },
+    ])
+    run_dotbot()
+
+    assert not os.path.exists(os.path.join(home, ".config", "baz"))
+    assert not os.path.exists(os.path.join(home, ".config", "fiz"))
+
+    assert not os.path.islink(os.path.join(home, ".config"))
+    assert not os.path.islink(os.path.join(home, ".config", "foo"))
+    assert not os.path.islink(os.path.join(home, ".config", "bar"))
+    assert os.path.islink(os.path.join(home, ".config", "foo", "a"))
+    with open(os.path.join(home, ".config", "foo", "a")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, ".config", "bar", "b")) as file:
+        assert file.read() == "banana"
+    with open(os.path.join(home, ".config", "bar", "c")) as file:
+        assert file.read() == "cherry"
+
+
+def test_link_glob_multi_star(home, dotfiles, run_dotbot):
+    """Verify link globbing with deep-nested stars."""
+
+    dotfiles.write("config/foo/a", "apple")
+    dotfiles.write("config/bar/b", "banana")
+    dotfiles.write("config/bar/c", "cherry")
+    dotfiles.write_config([
+        {"defaults": {"link": {"glob": True, "create": True}}},
+        {"link": {"~/.config/": "config/*/*"}},
+    ])
+    run_dotbot()
+
+    assert not os.path.islink(os.path.join(home, ".config"))
+    assert not os.path.islink(os.path.join(home, ".config", "foo"))
+    assert not os.path.islink(os.path.join(home, ".config", "bar"))
+    assert os.path.islink(os.path.join(home, ".config", "foo", "a"))
+    with open(os.path.join(home, ".config", "foo", "a")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, ".config", "bar", "b")) as file:
+        assert file.read() == "banana"
+    with open(os.path.join(home, ".config", "bar", "c")) as file:
+        assert file.read() == "cherry"
+
+
+@pytest.mark.parametrize(
+    "pattern, expect_file",
+    (
+        ("conf/*", lambda fruit: fruit),
+        ("conf/.*", lambda fruit: "." + fruit),
+        ("conf/[bc]*", lambda fruit: fruit if fruit[0] in "bc" else None),
+        ("conf/*e", lambda fruit: fruit if fruit[-1] == "e" else None),
+        ("conf/??r*", lambda fruit: fruit if fruit[2] == "r" else None),
+    )
+)
+def test_link_glob_patterns(pattern, expect_file, home, dotfiles, run_dotbot):
+    """Verify link glob pattern matching."""
+
+    fruits = ["apple", "apricot", "banana", "cherry", "currant", "cantalope"]
+    [dotfiles.write("conf/" + fruit, fruit) for fruit in fruits]
+    [dotfiles.write("conf/." + fruit, "dot-" + fruit) for fruit in fruits]
+    dotfiles.write_config([
+        {"defaults": {"link": {"glob": True, "create": True}}},
+        {"link": {"~/globtest": pattern}},
+    ])
+    run_dotbot()
+
+    for fruit in fruits:
+        if expect_file(fruit) is None:
+            assert not os.path.exists(os.path.join(home, "globtest", fruit))
+            assert not os.path.exists(os.path.join(home, "globtest", "." + fruit))
+        elif "." in expect_file(fruit):
+            assert not os.path.islink(os.path.join(home, "globtest", fruit))
+            assert os.path.islink(os.path.join(home, "globtest", "." + fruit))
+        else:  # "." not in expect_file(fruit)
+            assert os.path.islink(os.path.join(home, "globtest", fruit))
+            assert not os.path.islink(os.path.join(home, "globtest", "." + fruit))
+
+
+@pytest.mark.skipif(
+    "sys.version_info < (3, 5)",
+    reason="Python 3.5 required for ** globbing",
+)
+def test_link_glob_recursive(home, dotfiles, run_dotbot):
+    """Verify recursive link globbing and exclusions."""
+
+    dotfiles.write("config/foo/bar/a", "apple")
+    dotfiles.write("config/foo/bar/b", "banana")
+    dotfiles.write("config/foo/bar/c", "cherry")
+    dotfiles.write_config([
+        {"defaults": {"link": {"glob": True, "create": True}}},
+        {"link": {"~/.config/": {"path": "config/**", "exclude": ["config/**/b"]}}},
+    ])
+    run_dotbot()
+
+    assert not os.path.islink(os.path.join(home, ".config"))
+    assert not os.path.islink(os.path.join(home, ".config", "foo"))
+    assert not os.path.islink(os.path.join(home, ".config", "foo", "bar"))
+    assert os.path.islink(os.path.join(home, ".config", "foo", "bar", "a"))
+    assert not os.path.exists(os.path.join(home, ".config", "foo", "bar", "b"))
+    assert os.path.islink(os.path.join(home, ".config", "foo", "bar", "c"))
+    with open(os.path.join(home, ".config", "foo", "bar", "a")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, ".config", "foo", "bar", "c")) as file:
+        assert file.read() == "cherry"
+
+
+@pytest.mark.skipif(
+    "sys.platform[:5] == 'win32'",
+    reason="These if commands won't run on Windows",
+)
+def test_link_if(home, dotfiles, run_dotbot):
+    """Verify 'if' directives are checked when linking."""
+
+    os.mkdir(os.path.join(home, "d"))
+    dotfiles.write("f", "apple")
+    dotfiles.write_config([{
+        "link": {
+            "~/.f": {"path": "f", "if": "true"},
+            "~/.g": {"path": "f", "if": "false"},
+            "~/.h": {"path": "f", "if": "[ -d ~/d ]"},
+            "~/.i": {"path": "f", "if": "badcommand"},
+        },
+    }])
+    run_dotbot()
+
+    assert not os.path.exists(os.path.join(home, ".g"))
+    assert not os.path.exists(os.path.join(home, ".i"))
+    with open(os.path.join(home, ".f")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, ".h")) as file:
+        assert file.read() == "apple"
+
+
+@pytest.mark.skipif(
+    "sys.platform[:5] == 'win32'",
+    reason="These if commands won't run on Windows.",
+)
+def test_link_if_defaults(home, dotfiles, run_dotbot):
+    """Verify 'if' directive defaults are checked when linking."""
+
+    os.mkdir(os.path.join(home, "d"))
+    dotfiles.write("f", "apple")
+    dotfiles.write_config([
+        {
+            "defaults": {
+                "link": {
+                    "if": "false",
+                },
+            },
+        },
+        {
+            "link": {
+                "~/.j": {"path": "f", "if": "true"},
+                "~/.k": {"path": "f"},  # default is false
+            },
+        },
+    ])
+    run_dotbot()
+
+    assert not os.path.exists(os.path.join(home, ".k"))
+    with open(os.path.join(home, ".j")) as file:
+        assert file.read() == "apple"
+
+
+@pytest.mark.skipif(
+    "sys.platform[:5] != 'win32'",
+    reason="These if commands only run on Windows.",
+)
+def test_link_if_windows(home, dotfiles, run_dotbot):
+    """Verify 'if' directives are checked when linking (Windows only)."""
+
+    os.mkdir(os.path.join(home, "d"))
+    dotfiles.write("f", "apple")
+    dotfiles.write_config([{
+        "link": {
+            "~/.f": {"path": "f", "if": 'cmd /c "exit 0"'},
+            "~/.g": {"path": "f", "if": 'cmd /c "exit 1"'},
+            "~/.h": {"path": "f", "if": 'cmd /c "dir %USERPROFILE%\\d'},
+            "~/.i": {"path": "f", "if": 'cmd /c "badcommand"'},
+        },
+    }])
+    run_dotbot()
+
+    assert not os.path.exists(os.path.join(home, ".g"))
+    assert not os.path.exists(os.path.join(home, ".i"))
+    with open(os.path.join(home, ".f")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, ".h")) as file:
+        assert file.read() == "apple"
+
+
+@pytest.mark.skipif(
+    "sys.platform[:5] != 'win32'",
+    reason="These if commands only run on Windows",
+)
+def test_link_if_defaults_windows(home, dotfiles, run_dotbot):
+    """Verify 'if' directive defaults are checked when linking (Windows only)."""
+
+    os.mkdir(os.path.join(home, "d"))
+    dotfiles.write("f", "apple")
+    dotfiles.write_config([
+        {
+            "defaults": {
+                "link": {
+                    "if": 'cmd /c "exit 1"',
+                },
+            },
+        },
+        {
+            "link": {
+                "~/.j": {"path": "f", "if": 'cmd /c "exit 0"'},
+                "~/.k": {"path": "f"},  # default is false
+            },
+        },
+    ])
+    run_dotbot()
+
+    assert not os.path.exists(os.path.join(home, ".k"))
+    with open(os.path.join(home, ".j")) as file:
+        assert file.read() == "apple"
+
+
+@pytest.mark.parametrize("ignore_missing", (True, False))
+def test_link_ignore_missing(ignore_missing, home, dotfiles, run_dotbot):
+    """Verify link 'ignore_missing' is respected when the target is missing."""
+
+    dotfiles.write_config([{
+        "link": {
+            "~/missing_link": {
+                "path": "missing",
+                "ignore-missing": ignore_missing,
+            },
+        },
+    }])
+
+    if ignore_missing:
+        run_dotbot()
+        assert os.path.islink(os.path.join(home, "missing_link"))
+    else:
+        with pytest.raises(SystemExit):
+            run_dotbot()
+
+
+def test_link_leaves_file(home, dotfiles, run_dotbot):
+    """Verify relink does not overwrite file."""
+
+    dotfiles.write("f", "apple")
+    with open(os.path.join(home, ".f"), "w") as file:
+        file.write("grape")
+    dotfiles.write_config([{"link": {"~/.f": "f"}}])
+    with pytest.raises(SystemExit):
+        run_dotbot()
+
+    with open(os.path.join(home, ".f"), "r") as file:
+        assert file.read() == "grape"
+
+
+@pytest.mark.parametrize("key", ("canonicalize-path", "canonicalize"))
+def test_link_no_canonicalize(key, home, dotfiles, run_dotbot):
+    """Verify link canonicalization can be disabled."""
+
+    dotfiles.write("f", "apple")
+    dotfiles.write_config([
+        {"defaults": {"link": {key: False}}},
+        {"link": {"~/.f": {"path": "f"}}}
+    ])
+    try:
+        os.symlink(
+            dotfiles.directory,
+            os.path.join(home, "dotfiles-symlink"),
+            target_is_directory=True,
+        )
+    except TypeError:
+        # Python 2 compatibility:
+        # target_is_directory is only consistently available after Python 3.3.
+        os.symlink(
+            dotfiles.directory,
+            os.path.join(home, "dotfiles-symlink"),
+        )
+    run_dotbot(
+        "-c",
+        os.path.join(home, "dotfiles-symlink", os.path.basename(dotfiles.config_filename)),
+        custom=True,
+    )
+    assert "dotfiles-symlink" in os.readlink(os.path.join(home, ".f"))
+
+
+def test_link_prefix(home, dotfiles, run_dotbot):
+    """Verify link prefixes are prepended."""
+
+    dotfiles.write("conf/a", "apple")
+    dotfiles.write("conf/b", "banana")
+    dotfiles.write("conf/c", "cherry")
+    dotfiles.write_config([{
+        "link": {
+            "~/": {
+                "glob": True,
+                "path": "conf/*",
+                "prefix": ".",
+            },
+        },
+    }])
+    run_dotbot()
+    with open(os.path.join(home, ".a")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, ".b")) as file:
+        assert file.read() == "banana"
+    with open(os.path.join(home, ".c")) as file:
+        assert file.read() == "cherry"
+
+
+def test_link_relative(home, dotfiles, run_dotbot):
+    """Test relative linking works."""
+
+    dotfiles.write("f", "apple")
+    dotfiles.write("d/e", "grape")
+    dotfiles.write_config([{
+        "link": {
+            "~/.f": {
+                "path": "f",
+            },
+            "~/.frel": {
+                "path": "f",
+                "relative": True,
+            },
+            "~/nested/.frel": {
+                "path": "f",
+                "relative": True,
+                "create": True,
+            },
+            "~/.d": {
+                "path": "d",
+                "relative": True,
+            },
+        },
+    }])
+    run_dotbot()
+
+    f = os.readlink(os.path.join(home, ".f"))
+    if sys.platform[:5] == "win32" and f.startswith("\\\\?\\"):
+        f = f[4:]
+    assert f == os.path.join(dotfiles.directory, "f")
+
+    frel = os.readlink(os.path.join(home, ".frel"))
+    if sys.platform[:5] == "win32" and frel.startswith("\\\\?\\"):
+        frel = frel[4:]
+    assert frel == os.path.normpath("../../dotfiles/f")
+
+    nested_frel = os.readlink(os.path.join(home, "nested", ".frel"))
+    if sys.platform[:5] == "win32" and nested_frel.startswith("\\\\?\\"):
+        nested_frel = nested_frel[4:]
+    assert nested_frel == os.path.normpath("../../../dotfiles/f")
+
+    d = os.readlink(os.path.join(home, ".d"))
+    if sys.platform[:5] == "win32" and d.startswith("\\\\?\\"):
+        d = d[4:]
+    assert d == os.path.normpath("../../dotfiles/d")
+
+    with open(os.path.join(home, ".f")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, ".frel")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, "nested", ".frel")) as file:
+        assert file.read() == "apple"
+    with open(os.path.join(home, ".d", "e")) as file:
+        assert file.read() == "grape"
+
+
+def test_link_relink_leaves_file(home, dotfiles, run_dotbot):
+    """Verify relink does not overwrite file."""
+
+    dotfiles.write("f", "apple")
+    with open(os.path.join(home, ".f"), "w") as file:
+        file.write("grape")
+    dotfiles.write_config([{"link": {"~/.f": {"path": "f", "relink": True}}}])
+    with pytest.raises(SystemExit):
+        run_dotbot()
+    with open(os.path.join(home, ".f"), "r") as file:
+        assert file.read() == "grape"
+
+
+def test_link_relink_overwrite_symlink(home, dotfiles, run_dotbot):
+    """Verify relink overwrites symlinks."""
+
+    dotfiles.write("f", "apple")
+    with open(os.path.join(home, "f"), "w") as file:
+        file.write("grape")
+    os.symlink(os.path.join(home, "f"), os.path.join(home, ".f"))
+    dotfiles.write_config([{"link": {"~/.f": {"path": "f", "relink": True}}}])
+    run_dotbot()
+    with open(os.path.join(home, ".f"), "r") as file:
+        assert file.read() == "apple"
+
+
+def test_link_relink_relative_leaves_file(home, dotfiles, run_dotbot):
+    """Verify relink relative does not incorrectly relink file."""
+
+    dotfiles.write("f", "apple")
+    with open(os.path.join(home, ".f"), "w") as file:
+        file.write("grape")
+    config = [{
+        "link": {
+            "~/.folder/f": {
+                "path": "f",
+                "create": True,
+                "relative": True,
+            },
+        },
+    }]
+    dotfiles.write_config(config)
+    run_dotbot()
+
+    mtime = os.stat(os.path.join(home, ".folder", "f")).st_mtime
+
+    config[0]["link"]["~/.folder/f"]["relink"] = True
+    dotfiles.write_config(config)
+    run_dotbot()
+
+    new_mtime = os.stat(os.path.join(home, ".folder", "f")).st_mtime
+    assert mtime == new_mtime
+
+
+def test_link_defaults_1(home, dotfiles, run_dotbot):
+    """Verify that link doesn't overwrite non-dotfiles links by default."""
+
+    with open(os.path.join(home, "f"), "w") as file:
+        file.write("grape")
+    os.symlink(os.path.join(home, "f"), os.path.join(home, ".f"))
+    dotfiles.write("f", "apple")
+    dotfiles.write_config([{
+        "link": {"~/.f": "f"},
+    }])
+    with pytest.raises(SystemExit):
+        run_dotbot()
+
+    with open(os.path.join(home, ".f"), "r") as file:
+        assert file.read() == "grape"
+
+
+def test_link_defaults_2(home, dotfiles, run_dotbot):
+    """Verify that explicit link defaults override the implicit default."""
+
+    with open(os.path.join(home, "f"), "w") as file:
+        file.write("grape")
+    os.symlink(os.path.join(home, "f"), os.path.join(home, ".f"))
+    dotfiles.write("f", "apple")
+    dotfiles.write_config([
+        {"defaults": {"link": {"relink": True}}},
+        {"link": {"~/.f": "f"}},
+    ])
+    run_dotbot()
+
+    with open(os.path.join(home, ".f"), "r") as file:
+        assert file.read() == "apple"