Refactor context loading using execution event listener

execution.py deals with all execution logic. But cli.py, an outsider
module, may be interested in some events. For instance, when a user
changes their base URL using `cd`, we should reload the context from the
filesystem. This commit implements "execution event listener" to do such a
thing.

http_prompt/cli.py

@@ -15,7 +15,7 @@
 from . import config
 from .completer import HttpPromptCompleter
 from .context import Context
-from .contextio import load_context, save_context
+from .contextio import load_context, save_context, url_to_context_filename
 from .execution import execute
 from .lexer import HttpPromptLexer
 
@@ -30,6 +30,19 @@ def fix_incomplete_url(url):
     return url
 
 
+class ExecutionListener(object):
+
+    def url_changed(self, old_url, context):
+        # Load context from disk if base URL is changed
+        old_filename = url_to_context_filename(old_url)
+        new_filename = url_to_context_filename(context.url)
+        if old_filename != new_filename:
+            load_context(context)
+
+    def context_changed(self, context):
+        save_context(context)
+
+
 @click.command(context_settings=dict(
     ignore_unknown_options=True,
 ))
@@ -69,9 +82,10 @@ def cli(url, http_options):
     else:
         style = style_from_pygments(style)
 
+    listener = ExecutionListener()
+
     # Execute default HTTPie options
-    execute(' '.join(http_options), context)
-    save_context(context)
+    execute(' '.join(http_options), context, listener=listener)
 
     while True:
         try:
@@ -80,8 +94,7 @@ def cli(url, http_options):
         except EOFError:
             break  # Control-D pressed
         else:
-            execute(text, context)
-            save_context(context)
+            execute(text, context, listener=listener)
             if context.should_exit:
                 break
 

http_prompt/context.py

@@ -87,4 +87,4 @@ def json_obj(self):
         return obj
 
     def load_from_json_obj(self, json_obj):
-        self.__dict__ = deepcopy(json_obj)
+        self.__dict__.update(deepcopy(json_obj))

http_prompt/contextio.py

@@ -8,11 +8,14 @@
 from . import xdg
 
 
+# Don't save these attributes of a Context object
+EXCLUDED_ATTRS = ['url', 'should_exit']
+
 # Don't save these HTTPie options to avoid collision with user config file
 EXCLUDED_OPTIONS = ['--style']
 
 
-def _url_to_filename(url):
+def url_to_context_filename(url):
     r = urlparse(url)
     host = r.hostname
     port = r.port
@@ -24,7 +27,7 @@ def _url_to_filename(url):
 def load_context(context):
     """Load a Context object in place from user data directory."""
     dir_path = xdg.get_data_dir('context')
-    filename = _url_to_filename(context.url)
+    filename = url_to_context_filename(context.url)
     file_path = os.path.join(dir_path, filename)
     if os.path.exists(file_path):
         with open(file_path) as f:
@@ -36,10 +39,13 @@ def load_context(context):
 def save_context(context):
     """Save a Context object to user data directory."""
     dir_path = xdg.get_data_dir('context')
-    filename = _url_to_filename(context.url)
+    filename = url_to_context_filename(context.url)
     file_path = os.path.join(dir_path, filename)
     json_obj = context.json_obj()
 
+    for name in EXCLUDED_ATTRS:
+        json_obj.pop(name, None)
+
     options = json_obj['options']
     for name in EXCLUDED_OPTIONS:
         options.pop(name, None)

http_prompt/execution.py

@@ -113,16 +113,27 @@ def generate_cmds_with_explanations(summary, cmds):
     return text
 
 
+class DummyExecutionListener(object):
+
+    def url_changed(self, old_url, context):
+        pass
+
+    def context_changed(self, context):
+        pass
+
+
 class ExecutionVisitor(NodeVisitor):
 
-    def __init__(self, context):
+    def __init__(self, context, listener=None):
         super(ExecutionVisitor, self).__init__()
         self.context = context
 
         self.context_override = Context(context.url)
         self.method = None
         self.tool = None
 
+        self.listener = listener if listener else DummyExecutionListener()
+
     def visit_method(self, node, children):
         self.method = node.text
         return node
@@ -135,6 +146,10 @@ def visit_urlpath(self, node, children):
     def visit_cd(self, node, children):
         _, _, _, path, _ = children
         self.context_override.url = urljoin2(self.context_override.url, path)
+
+        if self.context_override.url != self.context.url:
+            self.listener.url_changed(self.context.url, self.context_override)
+
         return node
 
     def visit_rm(self, node, children):
@@ -259,6 +274,7 @@ def visit_tool(self, node, children):
 
     def visit_mutation(self, node, children):
         self.context.update(self.context_override)
+        self.listener.context_changed(self.context)
         return node
 
     def _final_context(self):
@@ -306,15 +322,15 @@ def generic_visit(self, node, children):
         return node
 
 
-def execute(command, context):
+def execute(command, context, listener=None):
     try:
         root = grammar.parse(command)
     except ParseError as err:
         # TODO: Better error message
         part = command[err.pos:err.pos + 10]
         click.secho('Syntax error near "%s"' % part, err=True, fg='red')
     else:
-        visitor = ExecutionVisitor(context)
+        visitor = ExecutionVisitor(context, listener=listener)
         try:
             visitor.visit(root)
         except VisitationError as err:

tests/test_cli.py

@@ -1,25 +1,36 @@
 import os
 
 from click.testing import CliRunner
-from mock import patch
+from mock import patch, DEFAULT
 
 from .base import TempAppDirTestCase
 from http_prompt import xdg
 from http_prompt.cli import cli, execute
 
 
-@patch('http_prompt.cli.prompt')
-@patch('http_prompt.cli.execute')
-def run_and_exit(args, execute_mock, prompt_mock):
-    """Run http-prompt executable and exit immediately."""
-    # Emulate a Ctrl+D on first call.
-    prompt_mock.side_effect = EOFError
-    execute_mock.side_effect = execute
+def run_and_exit(cli_args=None, prompt_commands=None):
+    """Run http-prompt executable, execute some prompt commands, and exit."""
+    if cli_args is None:
+        cli_args = []
 
-    runner = CliRunner()
-    result = runner.invoke(cli, args)
+    # Make sure last command is 'exit'
+    if prompt_commands is None:
+        prompt_commands = ['exit']
+    else:
+        prompt_commands += ['exit']
+
+    with patch.multiple('http_prompt.cli',
+                        prompt=DEFAULT, execute=DEFAULT) as mocks:
+        mocks['execute'].side_effect = execute
+
+        # prompt() is mocked to return the command in 'prompt_commands' in
+        # sequence, i.e., prompt() returns prompt_commands[i-1] when it is
+        # called for the ith time
+        mocks['prompt'].side_effect = prompt_commands
+
+        result = CliRunner().invoke(cli, cli_args)
+        context = mocks['execute'].call_args[0][1]
 
-    context = execute_mock.call_args[0][1]
     return result, context
 
 
@@ -99,3 +110,30 @@ def test_config_file(self):
         result, context = run_and_exit(['//example.com'])
         self.assertEqual(result.exit_code, 0)
         self.assertTrue(os.path.exists(config_path))
+
+    def test_base_url_changed(self):
+        result, context = run_and_exit(['example.com', 'name=bob', 'id==10'])
+        self.assertEqual(result.exit_code, 0)
+        self.assertEqual(context.url, 'http://example.com')
+        self.assertEqual(context.options, {})
+        self.assertEqual(context.body_params, {'name': 'bob'})
+        self.assertEqual(context.headers, {})
+        self.assertEqual(context.querystring_params, {'id': '10'})
+
+        # Changing hostname should trigger a context reload
+        result, context = run_and_exit(['localhost'],
+                                       ['cd http://example.com/api'])
+        self.assertEqual(result.exit_code, 0)
+        self.assertEqual(context.url, 'http://example.com/api')
+        self.assertEqual(context.options, {})
+        self.assertEqual(context.body_params, {'name': 'bob'})
+        self.assertEqual(context.headers, {})
+        self.assertEqual(context.querystring_params, {'id': '10'})
+
+    @patch('http_prompt.cli.prompt')
+    @patch('http_prompt.cli.execute')
+    def test_press_ctrl_d(self, execute_mock, prompt_mock):
+        prompt_mock.side_effect = EOFError
+        execute_mock.side_effect = execute
+        result = CliRunner().invoke(cli, [])
+        self.assertEqual(result.exit_code, 0)