Add configurable port and browser behavior for autobuild

CONTRIBUTING.md

@@ -249,6 +249,14 @@ Alternatively, to automatically rebuild the docs when changes occur, you can inv
 nox -s autobuild
 ```
 
+By default, this serves docs on port ``8000`` and opens your default browser.
+You can customize this behavior with environment variables:
+
+```shell
+SPYDER_DOCS_AUTOBUILD_PORT=8765 nox -s autobuild
+SPYDER_DOCS_AUTOBUILD_OPEN_BROWSER=0 nox -s autobuild
+```
+
 You can also pass your own custom [Sphinx build options](https://www.sphinx-doc.org/en/master/man/sphinx-build.html) after a ``--`` separator which are added to the default set.
 For example, to rebuild just the install guide and FAQ in verbose mode with the ``dirhtml`` builder (our noxfile automatically prepends the source directory for you, so typing the full relative path is optional):
 

noxfile.py

@@ -46,6 +46,9 @@
 
 SERVE_IP = "127.0.0.1"
 SERVE_PORT = 5000
+AUTOBUILD_PORT = 8000
+AUTOBUILD_PORT_ENV_VAR = "SPYDER_DOCS_AUTOBUILD_PORT"
+AUTOBUILD_OPEN_BROWSER_ENV_VAR = "SPYDER_DOCS_AUTOBUILD_OPEN_BROWSER"
 
 LINT_INVOCATION = ("prek",)
 
@@ -130,6 +133,14 @@ def process_filenames(filenames, source_dir=SOURCE_DIR):
     return filenames
 
 
+def env_var_to_bool(var_name, *, default):
+    """Convert an environment variable to bool with common false values."""
+    value = os.environ.get(var_name)
+    if value is None:
+        return default
+    return value.strip().lower() not in {"0", "false", "no", "off"}
+
+
 def extract_option_values(options, option_names, *, split_csv=False):
     """Extract particular option values from a sequence of options."""
     option_values = []
@@ -431,17 +442,26 @@ def _autodocs(session):
     """Use Sphinx-Autobuild to rebuild the project and open in browser."""
     session.install("sphinx-autobuild")
 
+    autobuild_port = os.environ.get(
+        AUTOBUILD_PORT_ENV_VAR, str(AUTOBUILD_PORT)
+    )
+    open_browser = env_var_to_bool(
+        AUTOBUILD_OPEN_BROWSER_ENV_VAR, default=True
+    )
+    autobuild_invocation = [
+        "sphinx-autobuild",
+        f"--port={autobuild_port}",
+        f"--watch={SOURCE_DIR}",
+    ]
+    if open_browser:
+        autobuild_invocation.append("--open-browser")
+
     with tempfile.TemporaryDirectory() as destination:
         sphinx_invocation = construct_sphinx_invocation(
             posargs=session.posargs[1:],
             build_dir=destination,
             extra_options=["-a"],
-            build_invocation=[
-                "sphinx-autobuild",
-                "--port=0",
-                f"--watch={SOURCE_DIR}",
-                "--open-browser",
-            ],
+            build_invocation=autobuild_invocation,
         )
         session.run(*sphinx_invocation)