feat: add linter for nix files with nix-instantiate

README.md

@@ -18,6 +18,9 @@ Adds [nix](https://nixos.org/) language support for VSCode Editor.
   + with the help of [nixpkgs-format](https://github.com/nix-community/nixpkgs-fmt)
 * Error Report
   + Using `nix-instantiate` errors reported
+
+  ![](./images/docs/linting.png)
+
 * Snippets
 
 ## Todos

package.json

@@ -11,8 +11,13 @@
   },
   "categories": [
     "Programming Languages",
+    "Formatters",
     "Snippets"
   ],
+  "keywords": [
+    "nix",
+    "IDE"
+  ],
   "bugs": {
     "url": "https://github.com/jnoortheen/vscode-nix-ide/issues"
   },
@@ -23,7 +28,7 @@
   },
   "main": "dist/extension.js",
   "activationEvents": [
-    "*"
+    "onLanguage:nix"
   ],
   "contributes": {
     "languages": [

src/extension.ts

@@ -1,6 +1,7 @@
 import * as vscode from "vscode";
 import { ExtensionContext } from "vscode";
 import { formattingProviders } from "./formatter";
+import { startLinting } from "./linter";
 
 /**
  * Activate this extension.
@@ -12,7 +13,7 @@ import { formattingProviders } from "./formatter";
  * @return A promise for the initialization
  */
 export const activate = async (context: ExtensionContext): Promise<any> => {
-  // startLinting(context);
+  startLinting(context);
 
   let subs = [
     vscode.languages.registerDocumentFormattingEditProvider,

src/linter.ts

@@ -0,0 +1,113 @@
+"use strict";
+
+import * as vscode from "vscode";
+import { Diagnostic, ExtensionContext, TextDocument } from "vscode";
+import { runInWorkspace } from "./process-runner";
+
+/**
+ * Whether a given document is saved to disk and in Nix language.
+ *
+ * @param document The document to check
+ * @return Whether the document is a Nix document saved to disk
+ */
+const isSavedDocument = (document: TextDocument): boolean =>
+  !document.isDirty &&
+  0 <
+    vscode.languages.match(
+      {
+        language: "nix",
+        scheme: "file",
+      },
+      document
+    );
+
+interface LintErrorType {
+  msg: string;
+  row: number;
+  col: number;
+}
+
+/**
+ * Exec pattern against the given text and return an array of all matches.
+ *
+ * @param text The output from nix-instantiate stderr
+ * @return All matches of pattern in text.
+ */
+const getErrors = (text: string): ReadonlyArray<LintErrorType> => {
+  const results = [];
+  const pattern = /^error: (.+), at .+:(\d+):(\d+)$/gm;
+  // We need to loop through the regexp here, so a let is required
+  let match = pattern.exec(text);
+  while (match !== null) {
+    results.push({
+      msg: match[1],
+      row: parseInt(match[2]),
+      col: parseInt(match[3]),
+    });
+    match = pattern.exec(text);
+  }
+  return results;
+};
+
+/**
+ * Parse errors from output for a given document.
+ *
+ * @param document The document to whose contents errors refer
+ * @param output The error output from shell.
+ * @return An array of all diagnostics
+ */
+const shellOutputToDiagnostics = (
+  document: TextDocument,
+  output: string
+): ReadonlyArray<Diagnostic> => {
+  const diagnostics: Array<Diagnostic> = [];
+  for (const err of getErrors(output)) {
+    const range = document.validateRange(
+      new vscode.Range(err.row - 1, err.col - 2, err.row - 1, err.col + 2)
+    );
+    const diagnostic = new Diagnostic(range, err.msg);
+    diagnostic.source = "nix";
+    diagnostics.push(diagnostic);
+  }
+  return diagnostics;
+};
+
+/**
+ * Start linting files.
+ *
+ * @param context The extension context
+ */
+export const startLinting = (context: ExtensionContext): void => {
+  const diagnostics = vscode.languages.createDiagnosticCollection("nix");
+  context.subscriptions.push(diagnostics);
+
+  const lint = async (document: TextDocument) => {
+    if (isSavedDocument(document)) {
+      const workspaceFolder = vscode.workspace.getWorkspaceFolder(document.uri);
+      try {
+        const result = await runInWorkspace(workspaceFolder, [
+          "nix-instantiate",
+          "--parse",
+          document.fileName,
+        ]);
+        var d = shellOutputToDiagnostics(document, result.stderr);
+      } catch (error) {
+        vscode.window.showErrorMessage(error.toString());
+        diagnostics.delete(document.uri);
+        return;
+      }
+      diagnostics.set(document.uri, d as Diagnostic[]);
+    }
+  };
+
+  vscode.workspace.onDidOpenTextDocument(lint, null, context.subscriptions);
+  vscode.workspace.onDidSaveTextDocument(lint, null, context.subscriptions);
+  vscode.workspace.textDocuments.forEach(lint);
+
+  // Remove diagnostics for closed files
+  vscode.workspace.onDidCloseTextDocument(
+    (d) => diagnostics.delete(d.uri),
+    null,
+    context.subscriptions
+  );
+};