Language server (finch lsp): diagnostics, hover, definition, completion, symbols, signature help; MSVC fix

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/lsp_test.py

@@ -0,0 +1,139 @@
+#!/usr/bin/env python3
+"""Talks to `finch lsp` like an editor would and checks the answers."""
+import json, os, subprocess, sys, tempfile
+
+FINCH = os.environ.get("FINCH", os.path.join(os.path.dirname(__file__), "..", "build", "finch"))
+failures = 0
+
+def check(name, cond, detail=""):
+    global failures
+    if cond:
+        print("ok  ", name)
+    else:
+        failures += 1
+        print("FAIL", name, detail)
+
+class Client:
+    def __init__(self):
+        self.p = subprocess.Popen([FINCH, "lsp"], stdin=subprocess.PIPE, stdout=subprocess.PIPE)
+        self.next_id = 0
+        self.notes = []
+
+    def send(self, msg):
+        body = json.dumps(msg).encode()
+        self.p.stdin.write(b"Content-Length: %d\r\n\r\n" % len(body) + body)
+        self.p.stdin.flush()
+
+    def read(self):
+        length = 0
+        while True:
+            line = self.p.stdout.readline().decode().strip()
+            if not line:
+                break
+            if line.startswith("Content-Length:"):
+                length = int(line.split(":")[1])
+        return json.loads(self.p.stdout.read(length))
+
+    def request(self, method, params):
+        self.next_id += 1
+        self.send({"jsonrpc": "2.0", "id": self.next_id, "method": method, "params": params})
+        while True:
+            m = self.read()
+            if m.get("id") == self.next_id:
+                return m.get("result")
+            self.notes.append(m)
+
+    def notify(self, method, params):
+        self.send({"jsonrpc": "2.0", "method": method, "params": params})
+
+    def diagnostics(self, uri):
+        # the server publishes right after didOpen/didChange; a request flushes the order
+        self.request("textDocument/hover", {"textDocument": {"uri": uri}, "position": {"line": 0, "character": 0}})
+        found = [n for n in self.notes if n.get("method") == "textDocument/publishDiagnostics" and n["params"]["uri"] == uri]
+        self.notes = []
+        return found[-1]["params"]["diagnostics"] if found else None
+
+src = """struct Point {
+    int x
+    int y
+}
+
+fn add(int a, int b) -> int {
+    return a + b
+}
+
+fn main() {
+    p := Point(1, 2)
+    total := add(p.x, p.y)
+    names := ["a", "b"]
+    print(total, names.len)
+}
+"""
+lines = src.split("\n")
+def pos(line_no, text):  # 0-based position of `text` in a 1-based line
+    return {"line": line_no - 1, "character": lines[line_no - 1].index(text)}
+
+d = tempfile.mkdtemp()
+path = os.path.join(d, "demo.fch")
+open(path, "w").write(src)
+uri = "file://" + path
+td = {"uri": uri}
+
+c = Client()
+init = c.request("initialize", {"processId": None, "rootUri": None, "capabilities": {}})
+check("initialize", init["capabilities"]["hoverProvider"] is True)
+c.notify("initialized", {})
+c.notify("textDocument/didOpen", {"textDocument": {"uri": uri, "languageId": "finch", "version": 1, "text": src}})
+check("no errors in a good file", c.diagnostics(uri) == [])
+
+h = c.request("textDocument/hover", {"textDocument": td, "position": pos(12, "total")})
+check("hover: variable type", h and "int total" in h["contents"]["value"], h)
+h = c.request("textDocument/hover", {"textDocument": td, "position": pos(12, "add")})
+check("hover: function signature", h and "fn add(int a, int b) -> int" in h["contents"]["value"], h)
+h = c.request("textDocument/hover", {"textDocument": td, "position": pos(14, "print")})
+check("hover: built-in docs", h and "Prints the values" in h["contents"]["value"], h)
+
+defn = c.request("textDocument/definition", {"textDocument": td, "position": pos(12, "add")})
+check("definition: function", defn and defn["range"]["start"]["line"] == 5, defn)
+defn = c.request("textDocument/definition", {"textDocument": td, "position": pos(12, "p.x")})
+check("definition: variable", defn and defn["range"]["start"]["line"] == 10, defn)
+
+# completion after "p." on a new line inside main
+edited = src.replace("    print(total, names.len)\n", "    print(total, names.len)\n    p.\n")
+c.notify("textDocument/didChange", {"textDocument": {"uri": uri, "version": 2}, "contentChanges": [{"text": edited}]})
+comp = c.request("textDocument/completion", {"textDocument": td, "position": {"line": 14, "character": 6}})
+labels = [i["label"] for i in comp["items"]]
+check("completion: struct fields after p.", "x" in labels and "y" in labels, labels)
+comp = c.request("textDocument/completion", {"textDocument": td, "position": {"line": 14, "character": 4}})
+labels = [i["label"] for i in comp["items"]]
+check("completion: variables, functions, keywords", all(x in labels for x in ["total", "names", "add", "Point", "while", "print"]), labels[:30])
+
+edited2 = src.replace("    print(total, names.len)\n", "    print(total, names.len)\n    names.\n")
+c.notify("textDocument/didChange", {"textDocument": {"uri": uri, "version": 3}, "contentChanges": [{"text": edited2}]})
+comp = c.request("textDocument/completion", {"textDocument": td, "position": {"line": 14, "character": 10}})
+labels = [i["label"] for i in comp["items"]]
+check("completion: array methods", "push" in labels and "sort" in labels, labels)
+
+sig_src = src.replace("    print(total, names.len)\n", "    print(total, names.len)\n    add(1, \n")
+c.notify("textDocument/didChange", {"textDocument": {"uri": uri, "version": 4}, "contentChanges": [{"text": sig_src}]})
+sig = c.request("textDocument/signatureHelp", {"textDocument": td, "position": {"line": 14, "character": 11}})
+check("signature help", sig and sig["signatures"][0]["label"].startswith("fn add") and sig["activeParameter"] == 1, sig)
+
+c.notify("textDocument/didChange", {"textDocument": {"uri": uri, "version": 5}, "contentChanges": [{"text": src}]})
+syms = c.request("textDocument/documentSymbol", {"textDocument": td})
+names = sorted(s["name"] for s in syms)
+check("document symbols", names == ["Point", "add", "main"], names)
+
+bad = src.replace("total := add(p.x, p.y)", 'total := add(p.x, "y")')
+c.notify("textDocument/didChange", {"textDocument": {"uri": uri, "version": 6}, "contentChanges": [{"text": bad}]})
+diags = c.diagnostics(uri)
+check("error shown while typing", diags and "must be int, but this is str" in diags[0]["message"] and diags[0]["range"]["start"]["line"] == 11, diags)
+c.notify("textDocument/didChange", {"textDocument": {"uri": uri, "version": 7}, "contentChanges": [{"text": src}]})
+check("error cleared after the fix", c.diagnostics(uri) == [])
+
+c.request("shutdown", None)
+c.notify("exit", None)
+c.p.wait(timeout=5)
+check("clean exit", c.p.returncode == 0, c.p.returncode)
+print("lsp:", "all ok" if failures == 0 else f"{failures} failed")
+sys.exit(1 if failures else 0)