lint(track_config): check key_features

[ee7]

This commit implements the below rules for a track's root config.json
file.

• The "key_features" key is optional
• The "key_features" value must be an array with length = 6
• The "key_features[].title" key is required
• The "key_features[].title" value must be a non-empty, non-blank
  string with length <= 25
• The "key_features[].content" key is required
• The "key_features[].content" value must be a non-empty, non-blank
  string with length <= 100

These rules are currently disabled until we have a list of valid icons:

• The "key_features[].icon" key is required
• The "key_features[].icon" value must be a string that matches one of
  the pre-defined icon values

See the spec:

• https://github.com/exercism/docs/blob/f7d5ec6fda07/building/configlet/lint.md#rule-configjson-file-is-valid

---

Questions for @ErikSchierboom:

1. The string here has a rune length of 100, but a len of 102 (it contains –, which is 3 bytes). Should we be checking for length or rune length?
2. Should we hide the icon errors for now?

This PR produces the following diff to the output of configlet lint, per track:

common-lisp

+The value of `content` that starts with `The language is very stabl...` is 102 characters, but must not exceed 100 characters:
+./config.json
+
+Configlet detected at least one problem.
+For more information on resolving the problems, please see the documentation:
+https://github.com/exercism/docs/blob/main/building/configlet/lint.md

julia

+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+

lua

+String is zero-length: 'icon':
+./config.json
+
+The value of `content` that starts with `Lua is primarily designed ...` is 167 characters, but must not exceed 100 characters:
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+The value of `content` that starts with `Lua is known to be one of ...` is 149 characters, but must not exceed 100 characters:
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+The value of `content` that starts with `Lua has a simple, yet powe...` is 112 characters, but must not exceed 100 characters:
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+The value of `content` that starts with `Lua offers a small, yet fl...` is 133 characters, but must not exceed 100 characters:
+./config.json
+
+Configlet detected at least one problem.
+For more information on resolving the problems, please see the documentation:
+https://github.com/exercism/docs/blob/main/building/configlet/lint.md

php

+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+Configlet detected at least one problem.
+For more information on resolving the problems, please see the documentation:
+https://github.com/exercism/docs/blob/main/building/configlet/lint.md

python

+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+String is zero-length: 'icon':
+./config.json
+
+Configlet detected at least one problem.
+For more information on resolving the problems, please see the documentation:
+https://github.com/exercism/docs/blob/main/building/configlet/lint.md

rust

+Missing key: 'icon':
+./config.json
+
+Missing key: 'icon':
+./config.json
+
+Missing key: 'icon':
+./config.json
+
+Missing key: 'icon':
+./config.json
+
+Missing key: 'icon':
+./config.json
+
+Missing key: 'icon':
+./config.json
+
+Configlet detected at least one problem.
+For more information on resolving the problems, please see the documentation:
+https://github.com/exercism/docs/blob/main/building/configlet/lint.md

[ErikSchierboom]

The string here has a rune length of 100, but a len of 102 (it contains –, which is 3 bytes). Should we be checking for length or rune length?

It is the number of runes.

Should we hide the icon errors for now?

We should

[ErikSchierboom]

LGTM

[ee7]

Current diff due to this PR:

lua

Ideally the below should say key_features.content, but that will have to wait for some later refactoring.

+The value of `content` that starts with `Lua is primarily designed...` is 167 characters, but must not exceed 100 characters:
+./config.json
+
+The value of `content` that starts with `Lua is known to be one of...` is 149 characters, but must not exceed 100 characters:
+./config.json
+
+The value of `content` that starts with `Lua has a simple, yet pow...` is 112 characters, but must not exceed 100 characters:
+./config.json
+
+The value of `content` that starts with `Lua offers a small, yet f...` is 133 characters, but must not exceed 100 characters:
+./config.json
+
+Configlet detected at least one problem.
+For more information on resolving the problems, please see the documentation:
+https://github.com/exercism/docs/blob/main/building/configlet/lint.md

[ee7]

@ErikSchierboom Non-blocking for this PR, but somewhat relevant: currently, we do not allow an optional string to be the empty string. Is that correct? We only allow it to be missing or null.

The current code is below. At the bottom, we have else not elif isRequired.

configlet/src/lint/validators.nim

Lines 42 to 51 in f9aacb6

	of JString:
	let s = data[key].getStr()
	if s.len > 0:
	if s.strip().len > 0:
	if not hasValidRuneLength(s, key, path, maxLen):
	result = false
	else:
	result.setFalseAndPrint("String is whitespace-only: " & q(key), path)
	else:
	result.setFalseAndPrint("String is zero-length: " & q(key), path)

[ErikSchierboom]

currently, we do not allow an optional string to be the empty string. Is that correct? We only allow it to be missing or null.

Hmmm. For now, I'd leave it like that. I do find that an empty string is something else than omitting a value or using null. We might revisit later, but for now this is good I think.