bsb-vscode-task-adaptor

A small Node.js script that reads the output from BuckleScript build tool (bsb) and adapts it so it can be consumed from vscode tasks, so they appear in the "Problems" panel of vscode that shows project diagnostics.

Getting started

Just three steps.

a. Install the package:

npm install --save-dev bsb-vscode-task-adaptor

or with yarn:

yarn add bsb-vscode-task-adaptor --dev

b. In your project main folder, create a folder .vscode and inside, a file tasks.json like the one shown below. The json will have npm and commands and two arguments passed in args:

1. parse-bsb is the name of this package script.
2. The command that parse-bsb will run by changing the second element passed to args (bsb -make-world -w in the example below).

Example tasks.json

{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "bsb watch",
      "command": "npx",
      "type": "shell",
      "args": ["parse-bsb", "bsb -make-world -w"],
      "group": {
        "kind": "build",
        "isDefault": true
      },
      "presentation": {
        "echo": true,
        "reveal": "always",
        "focus": false,
        "panel": "shared"
      },
      "isBackground": true,
      "problemMatcher": {
        "fileLocation": "absolute",
        "owner": "ocaml",
        "background": {
          "activeOnStart": true,
          "beginsPattern": ">>>> Start compiling",
          "endsPattern": ">>>> Finish compiling"
        },
        "pattern": [
          {
            "regexp": "^File \"(.*)\", lines (\\d+)-(\\d+)(?:, characters (\\d+)-(\\d+))?:$",
            "file": 1,
            "line": 2,
            "endLine": 3,
            "column": 4,
            "endColumn": 5
          },
          {
            "regexp": "^(?:(?:Parse\\s+)?([Ww]arning|[Ee]rror)(?:\\s+\\d+)?:)?\\s+(.*)$",
            "severity": 1,
            "message": 2
          }
        ]
      }
    }
  ]
}

c. Run the newly created task by pressing ⇧⌘B or from "Run Build Task" in the "Terminal" menu.

You should see the diagnostics appearing in vscode "Problems" panel.

Why

Some of the reasons why this tool might be useful for you:

• vscode problem matchers do not support multiline messages, so using a plain task would only show the first line of the message, leaving useful information out of the diagnostics panel. See microsoft/vscode#9635
• bsb uses super-errors by default for Reason projects. While super errors are really nice to better understand what's happening in the console, the format is very different from the original OCaml / BuckleScript errors, which makes them harder to parse. Unfortunately, super-errors can't be disabled for Reason projects and this configuration is not editable. See rescript-lang/rescript-compiler#3446
• Existing Reason / OCaml extensions for vscode that call bsb behind the scenes might lead to conflicts over files when the build commands are started manually too. The lack of transparency in the process leads often to confusion as well, as the output from bsb when it is called from the extension is not made visible for users. This adaptor shows the raw output from bsb, as well as the parsed string in the "Terminal" panel of vscode.