Build: Config Linter — Milestone 1

This is the module's real test. No new concepts — everything on this page is Module 1 material aimed at a real file. If any step sends you back to a lesson section, that's the system working.

Create the repo now — this becomes your first shipped tool:

mkdir configlint && cd configlint
git init
go mod init configlint

The assignment

Write a program that reads a YAML file line by line and reports what's in it. No structs, no YAML parser, no CLI framework — bufio.Scanner, string functions, maps, and counters.

go run . deployment.yaml

For each file given as an argument (os.Args[1:] — a slice of strings, use it like any slice):

1. Count key: value pairs (lines containing : that aren't comments)
2. Count comment lines (first non-space character is #) and blank lines
3. Track the deepest indentation you saw (leading spaces ÷ 2)
4. Print one summary line per file:

deployment.yaml: 24 keys, 3 comments, 2 blank, max depth 4

Test input

Save this as deployment.yaml in your repo:

# web deployment
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web
  labels:
    app: web
spec:
  replicas: 3
  template:
    spec:
      containers:
        - name: web
          image: nginx:latest
          env:
            - name: PORT
              value: "8080"

Done when

go run . deployment.yaml prints counts you've verified by hand against the file. Commit it.

Notice, before you move on, how the code feels: a handful of loose counters per file, passed around or printed in place. Nothing holds them together. Sit with that mild discomfort — Module 2 is about exactly that problem, and your first job there will be fixing it here.

Where this ends up: the finished tool is specced on the Config Linter project page — CLI flags, six rules, exit codes. Skim it for motivation if you like, but none of it is your job yet.