Dead code analysis editor mode via reanalyze (#334)

Author: zth

client/src/commands.ts

@@ -1,6 +1,10 @@
 import * as fs from "fs";
-import { window } from "vscode";
+import { window, DiagnosticCollection } from "vscode";
 import { LanguageClient, RequestType } from "vscode-languageclient/node";
+import {
+  DiagnosticsResultCodeActionsMap,
+  runDeadCodeAnalysisWithReanalyze,
+} from "./commands/dead_code_analysis";
 
 interface CreateInterfaceRequestParams {
   uri: string;
@@ -31,3 +35,15 @@ export const createInterface = (client: LanguageClient) => {
     uri: editor.document.uri.toString(),
   });
 };
+
+export const deadCodeAnalysisWithReanalyze = (
+  targetDir: string | null,
+  diagnosticsCollection: DiagnosticCollection,
+  diagnosticsResultCodeActions: DiagnosticsResultCodeActionsMap
+) => {
+  runDeadCodeAnalysisWithReanalyze(
+    targetDir,
+    diagnosticsCollection,
+    diagnosticsResultCodeActions
+  );
+};

client/src/commands/dead_code_analysis.ts

@@ -0,0 +1,259 @@
+import * as cp from "child_process";
+import * as path from "path";
+import {
+  window,
+  DiagnosticCollection,
+  Diagnostic,
+  Range,
+  Position,
+  DiagnosticSeverity,
+  Uri,
+  CodeAction,
+  CodeActionKind,
+  WorkspaceEdit,
+  DiagnosticTag,
+} from "vscode";
+
+export type DiagnosticsResultCodeActionsMap = Map<
+  string,
+  { range: Range; codeAction: CodeAction }[]
+>;
+
+let fileInfoRegex = /File "(.+)", line (\d+), characters ([\d-]+)/g;
+
+let extractFileInfo = (
+  fileInfo: string
+): {
+  filePath: string;
+  line: string;
+  characters: string;
+} | null => {
+  let m;
+
+  let filePath: string | null = null;
+  let line: string | null = null;
+  let characters: string | null = null;
+
+  while ((m = fileInfoRegex.exec(fileInfo)) !== null) {
+    if (m.index === fileInfoRegex.lastIndex) {
+      fileInfoRegex.lastIndex++;
+    }
+
+    m.forEach((match: string, groupIndex: number) => {
+      switch (groupIndex) {
+        case 1: {
+          filePath = match;
+          break;
+        }
+        case 2: {
+          line = match;
+          break;
+        }
+        case 3: {
+          characters = match;
+          break;
+        }
+      }
+    });
+  }
+
+  if (filePath != null && line != null && characters != null) {
+    return {
+      filePath,
+      line,
+      characters,
+    };
+  }
+
+  return null;
+};
+
+let dceTextToDiagnostics = (
+  dceText: string,
+  diagnosticsResultCodeActions: DiagnosticsResultCodeActionsMap
+): {
+  diagnosticsMap: Map<string, Diagnostic[]>;
+} => {
+  let diagnosticsMap: Map<string, Diagnostic[]> = new Map();
+
+  // Each section with a single issue found is seprated by two line breaks in
+  // the reanalyze output. The section contains information about the issue
+  // itself, what line/char and in what file it was found, as well as a
+  // suggestion for what you can replace the line containing the issue with to
+  // suppress the issue reported.
+  //
+  // Here's an example of how a section typically looks:
+  //
+  // Warning Dead Value
+  // File "/Users/zth/git/rescript-intro/src/Machine.res", line 2, characters 0-205
+  // +use is never used
+  // <-- line 2
+  // @dead("+use") let use = (initialState: 'a, handleEvent: ('a, 'b) => 'a) => {
+  dceText.split("\n\n").forEach((chunk) => {
+    let [
+      _title,
+      fileInfo,
+      text,
+
+      // These, if they exist, will power code actions for inserting the "fixed"
+      // line that reanalyze might suggest.
+      lineNumToReplace,
+      lineContentToReplace,
+    ] = chunk.split("\n");
+
+    let processedFileInfo = extractFileInfo(fileInfo);
+
+    if (processedFileInfo != null) {
+      let [startCharacter, endCharacter] =
+        processedFileInfo.characters.split("-");
+
+      let parsedLine = parseInt(processedFileInfo.line, 10);
+
+      let startPos = new Position(
+        // reanalyze reports lines as index 1 based, while VSCode wants them
+        // index 0 based. reanalyze reports diagnostics for an entire file on
+        // line 0 (and chars 0-0). So, we need to ensure that we don't give
+        // VSCode a negative line index, or it'll be sad.
+        Math.max(0, parsedLine - 1),
+        Math.max(0, parseInt(startCharacter, 10))
+      );
+
+      let endPos = new Position(
+        Math.max(0, parsedLine - 1),
+        Math.max(0, parseInt(endCharacter, 10))
+      );
+
+      // Detect if this diagnostic is for the entire file. If so, reanalyze will
+      // say that the issue is on line 0 and chars 0-0. This code below ensures
+      // that the full file is highlighted, if that's the case.
+      if (parsedLine === 0 && processedFileInfo.characters === "0-0") {
+        startPos = new Position(0, 0);
+        endPos = new Position(99999, 0);
+      }
+
+      let issueLocationRange = new Range(startPos, endPos);
+
+      let diagnostic = new Diagnostic(
+        issueLocationRange,
+        text.trim(),
+        DiagnosticSeverity.Warning
+      );
+
+      // This will render the part of the code as unused
+      diagnostic.tags = [DiagnosticTag.Unnecessary];
+
+      if (diagnosticsMap.has(processedFileInfo.filePath)) {
+        diagnosticsMap.get(processedFileInfo.filePath).push(diagnostic);
+      } else {
+        diagnosticsMap.set(processedFileInfo.filePath, [diagnostic]);
+      }
+
+      // If reanalyze suggests a fix, we'll set that up as a refactor code
+      // action in VSCode. This way, it'll be easy to suppress the issue
+      // reported if wanted. We also save the range of the issue, so we can
+      // leverage that to make looking up the code actions for each cursor
+      // position very cheap.
+      if (lineNumToReplace != null && lineContentToReplace != null) {
+        let actualLineToReplaceStr = lineNumToReplace.split("<-- line ").pop();
+
+        if (actualLineToReplaceStr != null) {
+          let codeAction = new CodeAction(`Suppress dead code warning`);
+          codeAction.kind = CodeActionKind.RefactorRewrite;
+
+          let codeActionEdit = new WorkspaceEdit();
+
+          // In the future, it would be cool to have an additional code action
+          // here for automatically removing whatever the thing that's dead is.
+          codeActionEdit.replace(
+            Uri.parse(processedFileInfo.filePath),
+            // Make sure the full line is replaced
+            new Range(
+              new Position(issueLocationRange.start.line, 0),
+              new Position(issueLocationRange.start.line, 999999)
+            ),
+            // reanalyze seems to add two extra spaces at the start of the line
+            // content to replace.
+            lineContentToReplace.slice(2)
+          );
+
+          codeAction.edit = codeActionEdit;
+
+          if (diagnosticsResultCodeActions.has(processedFileInfo.filePath)) {
+            diagnosticsResultCodeActions
+              .get(processedFileInfo.filePath)
+              .push({ range: issueLocationRange, codeAction });
+          } else {
+            diagnosticsResultCodeActions.set(processedFileInfo.filePath, [
+              { range: issueLocationRange, codeAction },
+            ]);
+          }
+        }
+      }
+    }
+  });
+
+  return {
+    diagnosticsMap,
+  };
+};
+
+export const runDeadCodeAnalysisWithReanalyze = (
+  targetDir: string | null,
+  diagnosticsCollection: DiagnosticCollection,
+  diagnosticsResultCodeActions: DiagnosticsResultCodeActionsMap
+) => {
+  let currentDocument = window.activeTextEditor.document;
+  let cwd = targetDir ?? path.dirname(currentDocument.uri.fsPath);
+
+  let p = cp.spawn("npx", ["reanalyze", "-dce"], {
+    cwd,
+  });
+
+  if (p.stdout == null) {
+    window.showErrorMessage("Something went wrong.");
+    return;
+  }
+
+  let data = "";
+
+  p.stdout.on("data", (d) => {
+    data += d;
+  });
+
+  p.stderr?.on("data", (e) => {
+    // Sometimes the compiler artifacts has been corrupted in some way, and
+    // reanalyze will spit out a "End_of_file" exception. The solution is to
+    // clean and rebuild the ReScript project, which we can tell the user about
+    // here.
+    if (e.includes("End_of_file")) {
+      window.showErrorMessage(
+        `Something went wrong trying to run reanalyze. Please try cleaning and rebuilding your ReScript project.`
+      );
+    } else {
+      window.showErrorMessage(
+        `Something went wrong trying to run reanalyze: '${e}'`
+      );
+    }
+  });
+
+  p.on("close", () => {
+    diagnosticsResultCodeActions.clear();
+    let { diagnosticsMap } = dceTextToDiagnostics(
+      data,
+      diagnosticsResultCodeActions
+    );
+
+    // This smoothens the experience of the diagnostics updating a bit by
+    // clearing only the visible diagnostics that has been fixed after the
+    // updated diagnostics has been applied.
+    diagnosticsCollection.forEach((uri, _) => {
+      if (!diagnosticsMap.has(uri.fsPath)) {
+        diagnosticsCollection.delete(uri);
+      }
+    });
+
+    diagnosticsMap.forEach((diagnostics, filePath) => {
+      diagnosticsCollection.set(Uri.parse(filePath), diagnostics);
+    });
+  });
+};