Add dmypy support via mypy.api.run_dmypy

palantir/python-language-server#391

Update plugin flow for non-live-mode dmypy invocation via run_dmypy.

Minor fix to update detect `.mypy.ini` as well as `mypy.ini`.

Author: asford

README.rst

@@ -35,3 +35,18 @@ Depending on your editor, the configuration (found in a file called mypy-ls.cfg
 	"live_mode": True,
 	"strict": False
     }
+
+``dmypy`` (default is False) executes via `dmypy run` rather than `mypy`.
+
+This uses the `dmypy` daemon and may dramatically improve the responsiveness of the `pyls` server.
+
+Depending on your editor, the configuration (found in a file called mypy-ls.cfg in your workspace or a parent directory) should be roughly like this:
+
+::
+
+    {
+	"enabled": True,
+	"live_mode": False,
+	"dmypy": True,
+	"strict": False
+    }

mypy_ls/plugin.py

@@ -17,6 +17,7 @@
 from pyls.config.config import Config
 from typing import Optional, Dict, Any, IO, List
 import atexit
+import collections
 
 line_pattern: str = r"((?:^[a-z]:)?[^:]+):(?:(\d+):)?(?:(\d+):)? (\w+): (.*)"
 
@@ -26,6 +27,12 @@
 
 tmpFile: Optional[IO[str]] = None
 
+# In non-live-mode the file contents aren't updated.
+# Returning an empty diagnostic clears the diagnostic result,
+# so store a cache of last diagnostics for each file a-la the pylint plugin,
+# so we can return some potentially-stale diagnostics.
+# https://github.com/palantir/python-language-server/blob/0.36.2/pyls/plugins/pylint_lint.py#L52-L59
+last_diagnostics : Dict[str, List] = collections.defaultdict(list)
 
 def parse_line(line: str, document: Optional[Document] = None) -> Optional[Dict[str, Any]]:
     """
@@ -111,35 +118,77 @@ def pyls_lint(config: Config, workspace: Workspace, document: Document,
 
     """
     settings = config.plugin_settings('mypy-ls')
+    log.info(
+        "lint settings = %s document.path = %s is_saved = %s",
+        settings,
+        document.path,
+        is_saved
+    )
+
     live_mode = settings.get('live_mode', True)
-    args = ['--incremental',
-            '--show-column-numbers',
-            '--follow-imports', 'silent']
+    dmypy = settings.get("dmypy", False)
+
+    if dmypy and live_mode:
+        # dmypy can only be efficiently run on files that have been saved, see:
+        # https://github.com/python/mypy/issues/9309
+        log.warning("live_mode is not supported with dmypy, disabling")
+        live_mode = False
+
+    args = ['--show-column-numbers']
 
     global tmpFile
     if live_mode and not is_saved and tmpFile:
+        log.info("live_mode tmpFile = %s", live_mode)
         tmpFile = open(tmpFile.name, "w")
         tmpFile.write(document.source)
         tmpFile.close()
         args.extend(['--shadow-file', document.path, tmpFile.name])
-    elif not is_saved:
-        return []
+    elif not is_saved and document.path in last_diagnostics:
+        # On-launch the document isn't marked as saved, so fall through and run
+        # the diagnostics anyway even if the file contents may be out of date.
+        log.info(
+            "non-live, returning cached diagnostics len(cached) = %s",
+            last_diagnostics[document.path]
+        )
+        return last_diagnostics[document.path]
 
     if mypyConfigFile:
         args.append('--config-file')
         args.append(mypyConfigFile)
+
     args.append(document.path)
+
     if settings.get('strict', False):
         args.append('--strict')
 
-    report, errors, _ = mypy_api.run(args)
+    if not dmypy:
+        args.extend([
+            "--incremental",
+            "--follow-imports",
+            "silent"
+        ])
+
+        log.info(f"executing mypy {args=}")
+        report, errors, _ = mypy_api.run(args)
+    else:
+        args = ["run", "--"] + args
+
+        log.info(f"executing dmypy {args=}")
+        report, errors, _ = mypy_api.run_dmypy(args)
+
+    log.debug("report: \n" + report)
+    log.debug("errors: \n" + errors)
 
     diagnostics = []
     for line in report.splitlines():
+        log.debug(f"parsing: {line=}")
         diag = parse_line(line, document)
         if diag:
             diagnostics.append(diag)
 
+    logging.info("mypy-ls len(diagnostics) = %s", len(diagnostics))
+
+    last_diagnostics[document.path] = diagnostics
     return diagnostics
 
 
@@ -179,19 +228,27 @@ def init(workspace: str) -> Dict[str, str]:
 
     """
     # On windows the path contains \\ on linux it contains / all the code works with /
+    log.info(f"init {workspace=}")
     workspace = workspace.replace("\\", "/")
+
     configuration = {}
     path = findConfigFile(workspace, "mypy-ls.cfg")
     if path:
         with open(path) as file:
             configuration = eval(file.read())
+
     global mypyConfigFile
     mypyConfigFile = findConfigFile(workspace, "mypy.ini")
+    if not mypyConfigFile:
+        mypyConfigFile = findConfigFile(workspace, ".mypy.ini")
+
     if (("enabled" not in configuration or configuration["enabled"])
        and ("live_mode" not in configuration or configuration["live_mode"])):
         global tmpFile
         tmpFile = tempfile.NamedTemporaryFile('w', delete=False)
         tmpFile.close()
+
+    log.info(f"{mypyConfigFile=} {configuration=}")
     return configuration