Allow LSP test_file to autofill didOpen params from previous splits (#5078)

Currently file tests for LSP must provide carbon source code as an
escaped string within notify params, i.e.
```
[[@LSP-NOTIFY:textDocument/didOpen:
  "textDocument": {
    "uri": "file:/class.carbon",
    "languageId": "carbon",
    "text": "class A {\n  fn F();\n  fn G() {}\n}\n"
  }
]]
```

This works fine for simple, single line files but gets annoying when
working with more complicated files which are necessary when testing
more complicated features e.g. goto-definition

```
--- class.carbon
class A {
  fn F();
  fn G() {}
}
--- STDIN
[[@LSP-NOTIFY:textDocument/didOpen:
  "textDocument": {
    "uri": "file:/class.carbon",
    "languageId": "carbon",
    "text": "AUTOFILL"
  }
]]
```

This PR extends file_test_base to be able to parse the notify/call
params and inject files from the test_file's splits into the JSON input.
I purposely avoid using the clangd types and manually parse the
llvm::json::Value here to avoid introducing a depdendency on clangd to
the generic file_test_base, but happy to change if we think that is
fine. Also happy to accept other suggestions on alternative methods to
achieve same result.

---------

Co-authored-by: Jon Ross-Perkins <jperkins@google.com>

testing/file_test/README.md

@@ -116,6 +116,19 @@ Some keywords can be inserted for content:
         -   `id`: Assigned from `<id>`.
         -   `result`: Optionally assigned from `<extra content>`.
 
+    Additional substitutions are made to `<extra contents>` in the following
+    cases:
+
+    -   ```
+        [[@LSP-NOTIFY:textDocument/didOpen:"textDocument": {
+            "uri": "file:/<filename>",
+            "text": "FROM_FILE_SPLIT"
+        }]]
+        ```
+
+        The keyword `FROM_FILE_SPLIT` is substituted with the content of the
+        file split `<filename>`. All other properties are unchanged.
+
 -   ```
     [[@TEST_NAME]]
     ```

testing/file_test/test_file.cpp

@@ -6,7 +6,11 @@
 
 #include <fstream>
 
+#include "common/check.h"
+#include "common/error.h"
+#include "common/raw_string_ostream.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/JSON.h"
 #include "testing/base/file_helpers.h"
 
 namespace Carbon::Testing {
@@ -93,9 +97,54 @@ struct SplitState {
   int file_index = 0;
 };
 
+// Given a `file:/<filename>` URI, returns the filename.
+static auto ExtractFilePathFromUri(llvm::StringRef uri)
+    -> ErrorOr<llvm::StringRef> {
+  static constexpr llvm::StringRef FilePrefix = "file:/";
+  if (!uri.starts_with(FilePrefix)) {
+    return ErrorBuilder("uri `") << uri << "` is not a file uri";
+  }
+  return uri.drop_front(FilePrefix.size());
+}
+
+// When `FROM_FILE_SPLIT` is used in path `textDocument.text`, populate the
+// value from the split matching the `uri`. Only used for
+// `textDocument/didOpen`.
+static auto AutoFillDidOpenParams(llvm::json::Object* params,
+                                  llvm::ArrayRef<TestFile::Split> splits)
+    -> ErrorOr<Success> {
+  auto* text_document = params->getObject("textDocument");
+  if (text_document == nullptr) {
+    return Success();
+  }
+
+  auto attr_it = text_document->find("text");
+  if (attr_it == text_document->end() || attr_it->second != "FROM_FILE_SPLIT") {
+    return Success();
+  }
+
+  auto uri = text_document->getString("uri");
+  if (!uri) {
+    return Error("missing uri in params.textDocument");
+  }
+
+  CARBON_ASSIGN_OR_RETURN(auto file_path, ExtractFilePathFromUri(*uri));
+  const auto* split_it =
+      llvm::find_if(splits, [&](const TestFile::Split& split) {
+        return split.filename == file_path;
+      });
+  if (split_it == splits.end()) {
+    return ErrorBuilder() << "No split found for uri: " << *uri;
+  }
+  attr_it->second = split_it->content;
+  return Success();
+}
+
 // Reformats `[[@LSP:` and similar keyword as an LSP call with headers.
 static auto ReplaceLspKeywordAt(std::string* content, size_t keyword_pos,
-                                int& lsp_call_id) -> ErrorOr<size_t> {
+                                int& lsp_call_id,
+                                llvm::ArrayRef<TestFile::Split> splits)
+    -> ErrorOr<size_t> {
   llvm::StringRef content_at_keyword =
       llvm::StringRef(*content).substr(keyword_pos);
 
@@ -133,31 +182,50 @@ static auto ReplaceLspKeywordAt(std::string* content, size_t keyword_pos,
   llvm::StringRef body = body_start.take_front(body_end);
   auto [method_or_id, extra_content] = body.split(":");
 
-  // Form the JSON.
-  std::string json = llvm::formatv(R"({{"jsonrpc": "2.0", "{0}": "{1}")",
-                                   method_or_id_label, method_or_id);
-  if (use_call_id) {
-    // Omit quotes on the ID because we know it's an integer.
-    json += llvm::formatv(R"(, "id": {0})", ++lsp_call_id);
-  }
+  llvm::json::Value parsed_extra_content = nullptr;
   if (!extra_content.empty()) {
-    json += ",";
-    if (extra_content_label.empty()) {
-      if (!extra_content.starts_with("\n")) {
-        json += " ";
-      }
-      json += extra_content;
-    } else {
-      json += llvm::formatv(R"( "{0}": {{{1}})", extra_content_label,
-                            extra_content);
+    std::string extra_content_as_object =
+        llvm::formatv("{{{0}}", extra_content);
+    auto parse_result = llvm::json::parse(extra_content_as_object);
+    if (auto err = parse_result.takeError()) {
+      return ErrorBuilder() << "Error parsing extra content: " << err;
+    }
+    parsed_extra_content = std::move(*parse_result);
+    CARBON_CHECK(parsed_extra_content.kind() == llvm::json::Value::Object);
+    if (extra_content_label == "params" &&
+        method_or_id == "textDocument/didOpen") {
+      CARBON_RETURN_IF_ERROR(
+          AutoFillDidOpenParams(parsed_extra_content.getAsObject(), splits));
     }
   }
-  json += "}";
+
+  // Form the JSON.
+  RawStringOstream buffer;
+  llvm::json::OStream json(buffer);
+
+  json.object([&] {
+    json.attribute("jsonrpc", "2.0");
+    json.attribute(method_or_id_label, method_or_id);
+
+    if (use_call_id) {
+      json.attribute("id", ++lsp_call_id);
+    }
+    if (parsed_extra_content != nullptr) {
+      if (!extra_content_label.empty()) {
+        json.attribute(extra_content_label, parsed_extra_content);
+      } else {
+        for (const auto& [key, value] : *parsed_extra_content.getAsObject()) {
+          json.attribute(key, value);
+        }
+      }
+    }
+  });
 
   // Add the Content-Length header. The `2` accounts for extra newlines.
-  auto json_with_header =
-      llvm::formatv("Content-Length: {0}\n\n{1}\n", json.size() + 2, json)
-          .str();
+  int content_length = buffer.size() + 2;
+  auto json_with_header = llvm::formatv("Content-Length: {0}\n\n{1}\n",
+                                        content_length, buffer.TakeStr())
+                              .str();
   int keyword_len =
       (body_start.data() + body_end + LspEnd.size()) - keyword.data();
   content->replace(keyword_pos, keyword_len, json_with_header);
@@ -167,7 +235,8 @@ static auto ReplaceLspKeywordAt(std::string* content, size_t keyword_pos,
 // Replaces the keyword at the given position. Returns the position to start a
 // find for the next keyword.
 static auto ReplaceContentKeywordAt(std::string* content, size_t keyword_pos,
-                                    llvm::StringRef test_name, int& lsp_call_id)
+                                    llvm::StringRef test_name, int& lsp_call_id,
+                                    llvm::ArrayRef<TestFile::Split> splits)
     -> ErrorOr<size_t> {
   auto keyword = llvm::StringRef(*content).substr(keyword_pos);
 
@@ -186,7 +255,7 @@ static auto ReplaceContentKeywordAt(std::string* content, size_t keyword_pos,
   }
 
   if (keyword.starts_with("[[@LSP")) {
-    return ReplaceLspKeywordAt(content, keyword_pos, lsp_call_id);
+    return ReplaceLspKeywordAt(content, keyword_pos, lsp_call_id, splits);
   }
 
   return ErrorBuilder() << "Unexpected use of `[[@` at `"
@@ -198,7 +267,9 @@ static auto ReplaceContentKeywordAt(std::string* content, size_t keyword_pos,
 // TEST_NAME is the only content keyword at present, but we do validate that
 // other names are reserved.
 static auto ReplaceContentKeywords(llvm::StringRef filename,
-                                   std::string* content) -> ErrorOr<Success> {
+                                   std::string* content,
+                                   llvm::ArrayRef<TestFile::Split> splits)
+    -> ErrorOr<Success> {
   static constexpr llvm::StringLiteral Prefix = "[[@";
 
   auto keyword_pos = content->find(Prefix);
@@ -227,7 +298,8 @@ static auto ReplaceContentKeywords(llvm::StringRef filename,
   while (keyword_pos != std::string::npos) {
     CARBON_ASSIGN_OR_RETURN(
         auto keyword_end,
-        ReplaceContentKeywordAt(content, keyword_pos, test_name, lsp_call_id));
+        ReplaceContentKeywordAt(content, keyword_pos, test_name, lsp_call_id,
+                                splits));
     keyword_pos = content->find(Prefix, keyword_end);
   }
   return Success();
@@ -237,7 +309,8 @@ static auto ReplaceContentKeywords(llvm::StringRef filename,
 static auto AddSplit(llvm::StringRef filename, std::string* content,
                      llvm::SmallVector<TestFile::Split>* file_splits)
     -> ErrorOr<Success> {
-  CARBON_RETURN_IF_ERROR(ReplaceContentKeywords(filename, content));
+  CARBON_RETURN_IF_ERROR(
+      ReplaceContentKeywords(filename, content, *file_splits));
   file_splits->push_back(
       {.filename = filename.str(), .content = std::move(*content)});
   content->clear();
@@ -268,8 +341,9 @@ static auto TryConsumeSplit(llvm::StringRef line, llvm::StringRef line_trimmed,
     // If there's a split, all output is appended at the end of each file
     // before AUTOUPDATE. We may want to change that, but it's not
     // necessary to handle right now.
-    return ErrorBuilder() << "AUTOUPDATE/NOAUTOUPDATE setting must be in "
-                             "the first file.";
+    return Error(
+        "AUTOUPDATE/NOAUTOUPDATE setting must be in "
+        "the first file.");
   }
 
   // On a file split, add the previous file, then start a new one.
@@ -280,15 +354,16 @@ static auto TryConsumeSplit(llvm::StringRef line, llvm::StringRef line_trimmed,
     split->content.clear();
     if (split->found_code_pre_split) {
       // For the first split, we make sure there was no content prior.
-      return ErrorBuilder() << "When using split files, there must be no "
-                               "content before the first split file.";
+      return Error(
+          "When using split files, there must be no content before the first "
+          "split file.");
     }
   }
 
   ++split->file_index;
   split->filename = line_trimmed.trim();
   if (split->filename.empty()) {
-    return ErrorBuilder() << "Missing filename for split.";
+    return Error("Missing filename for split.");
   }
   // The split line is added to non_check_lines for retention in autoupdate, but
   // is not added to the test file content.
@@ -514,7 +589,7 @@ static auto TryConsumeAutoupdate(int line_index, llvm::StringRef line_trimmed,
     return false;
   }
   if (*found_autoupdate) {
-    return ErrorBuilder() << "Multiple AUTOUPDATE/NOAUTOUPDATE settings found";
+    return Error("Multiple AUTOUPDATE/NOAUTOUPDATE settings found");
   }
   *found_autoupdate = true;
   if (line_trimmed == Autoupdate) {

testing/file_test/testdata/lsp_autofill.carbon

@@ -0,0 +1,38 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// AUTOUPDATE
+// TIP: To test this file alone, run:
+// TIP:   bazel test //testing/file_test:file_test_base_test --test_arg=--file_tests=testing/file_test/testdata/lsp_autofill.carbon
+// TIP: To dump output, run:
+// TIP:   bazel run //testing/file_test:file_test_base_test -- --dump_output --file_tests=testing/file_test/testdata/lsp_autofill.carbon
+
+// --- foo.carbon
+class Foo {
+  fn foo();
+  fn bar() {}
+}
+
+// --- STDIN
+[[@LSP-NOTIFY:textDocument/didOpen:
+  "textDocument": {
+    "uri": "file:/foo.carbon",
+    "languageId": "carbon",
+    "text": "FROM_FILE_SPLIT"
+  }
+]]
+
+// --- AUTOUPDATE-SPLIT
+
+// CHECK:STDERR: --- STDIN:
+// CHECK:STDERR: Content-Length: 182
+// CHECK:STDERR:
+// CHECK:STDERR: {"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"languageId":"carbon","text":"class Foo {\n  fn foo();\n  fn bar() {}\n}\n\n","uri":"file:/foo.carbon"}}}
+// CHECK:STDERR:
+// CHECK:STDERR:
+// CHECK:STDOUT: 2 args: `default_args`, `foo.carbon`
+// CHECK:STDOUT: foo.carbon:1: class Foo {
+// CHECK:STDOUT: foo.carbon:2:   fn foo();
+// CHECK:STDOUT: foo.carbon:3:   fn bar() {}
+// CHECK:STDOUT: foo.carbon:4: }

testing/file_test/testdata/lsp_keywords.carbon

@@ -11,62 +11,57 @@
 // --- STDIN
 [[@LSP:foo:]]
 [[@LSP:foo]]
-[[@LSP:bar:content]]
+[[@LSP:bar:"content": 0]]
 [[@LSP:baz:
-multi
-line
+"multi": 0,
+"line": 1
 ]]
-[[@LSP-CALL:bar:content]]
+[[@LSP-CALL:bar:"content": 0]]
 [[@LSP-CALL:baz:
-multi
-line]]
+"multi": 0,
+"line": 1]]
 [[@LSP-REPLY:7]]
-[[@LSP-REPLY:8:bar]]
+[[@LSP-REPLY:8:"bar": 0]]
 [[@LSP-NOTIFY:exit]]
 
 // --- AUTOUPDATE-SPLIT
 
 // CHECK:STDERR: --- STDIN:
-// CHECK:STDERR: Content-Length: 37
+// CHECK:STDERR: Content-Length: 34
 // CHECK:STDERR:
-// CHECK:STDERR: {"jsonrpc": "2.0", "method": "foo"}
+// CHECK:STDERR: {"jsonrpc":"2.0","method":"foo"}
 // CHECK:STDERR:
-// CHECK:STDERR: Content-Length: 37
+// CHECK:STDERR: Content-Length: 34
 // CHECK:STDERR:
-// CHECK:STDERR: {"jsonrpc": "2.0", "method": "foo"}
+// CHECK:STDERR: {"jsonrpc":"2.0","method":"foo"}
 // CHECK:STDERR:
 // CHECK:STDERR: Content-Length: 46
 // CHECK:STDERR:
-// CHECK:STDERR: {"jsonrpc": "2.0", "method": "bar", content}
+// CHECK:STDERR: {"jsonrpc":"2.0","method":"bar","content":0}
 // CHECK:STDERR:
-// CHECK:STDERR: Content-Length: 50
+// CHECK:STDERR: Content-Length: 53
 // CHECK:STDERR:
-// CHECK:STDERR: {"jsonrpc": "2.0", "method": "baz",
-// CHECK:STDERR: multi
-// CHECK:STDERR: line
-// CHECK:STDERR: }
+// CHECK:STDERR: {"jsonrpc":"2.0","method":"baz","multi":0,"line":1}
 // CHECK:STDERR:
-// CHECK:STDERR: Content-Length: 67
+// CHECK:STDERR: Content-Length: 64
 // CHECK:STDERR:
-// CHECK:STDERR: {"jsonrpc": "2.0", "method": "bar", "id": 1, "params": {content}}
+// CHECK:STDERR: {"jsonrpc":"2.0","method":"bar","id":1,"params":{"content":0}}
 // CHECK:STDERR:
 // CHECK:STDERR: Content-Length: 71
 // CHECK:STDERR:
-// CHECK:STDERR: {"jsonrpc": "2.0", "method": "baz", "id": 2, "params": {
-// CHECK:STDERR: multi
-// CHECK:STDERR: line}}
+// CHECK:STDERR: {"jsonrpc":"2.0","method":"baz","id":2,"params":{"line":1,"multi":0}}
 // CHECK:STDERR:
-// CHECK:STDERR: Content-Length: 31
+// CHECK:STDERR: Content-Length: 28
 // CHECK:STDERR:
-// CHECK:STDERR: {"jsonrpc": "2.0", "id": "7"}
+// CHECK:STDERR: {"jsonrpc":"2.0","id":"7"}
 // CHECK:STDERR:
-// CHECK:STDERR: Content-Length: 48
+// CHECK:STDERR: Content-Length: 47
 // CHECK:STDERR:
-// CHECK:STDERR: {"jsonrpc": "2.0", "id": "8", "result": {bar}}
+// CHECK:STDERR: {"jsonrpc":"2.0","id":"8","result":{"bar":0}}
 // CHECK:STDERR:
-// CHECK:STDERR: Content-Length: 38
+// CHECK:STDERR: Content-Length: 35
 // CHECK:STDERR:
-// CHECK:STDERR: {"jsonrpc": "2.0", "method": "exit"}
+// CHECK:STDERR: {"jsonrpc":"2.0","method":"exit"}
 // CHECK:STDERR:
 // CHECK:STDERR:
 // CHECK:STDOUT: 1 args: `default_args`

toolchain/language_server/testdata/document_symbol/nested.carbon

@@ -8,10 +8,19 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/language_server/testdata/document_symbol/nested.carbon
 
+// --- class.carbon
+class A {
+  fn F();
+  fn G() {}
+}
+
 // --- STDIN
 [[@LSP-NOTIFY:textDocument/didOpen:
-  "textDocument": {"uri": "file:/class.carbon", "languageId": "carbon",
-                   "text": "class A {\n  fn F();\n  fn G() {}\n}\n"}
+  "textDocument": {
+    "uri": "file:/class.carbon",
+    "languageId": "carbon",
+    "text": "FROM_FILE_SPLIT"
+  }
 ]]
 [[@LSP-CALL:textDocument/documentSymbol:
   "textDocument": {"uri": "file:/class.carbon"}