Document snippet extension (#410)

Document snippet extension

Author: ErikSchierboom

building/configlet/lint.md

@@ -109,6 +109,8 @@ The `config.json` file should have the following checks:
   - The `"files.example` and `"files.exemplar"` files _can_ overlap
 - The `"test_runner.average_run_time"` key is required if `"status.test_runner"` is equal to `true`
 - The `"test_runner.average_run_time"` value must be a floating-point number > 0 with one decimal point of precision
+- The `"approaches.snippet_extension"` key is required if the track has one or more approaches
+- The `"approaches.snippet_extension"` value must be a non-blank string¹
 - The `"exercises"` key is required
 - The `"exercises.concept"` key is required
 - The `"exercises.concept"` value must be an array
@@ -375,10 +377,11 @@ The `config.json` file should have the following checks:
 - The Markdown must conform to the [Markdown standards](/docs/building/markdown/markdown)
 - Links must be absolute (relative links are not allowed)
 
-### Rule: exercises/{concept|practice}/<slug>/.approaches/<approach-slug>/snippet.txt is valid
+### Rule: exercises/{concept|practice}/<slug>/.approaches/<approach-slug>/snippet.<snippet-extension> is valid
 
 - The file's presence is required if a matching `"approaches[].slug"` entry exists in the `.approaches/config.json` file
 - The snippet must have at most 8 lines
+- The snippet extension is taken from the `approaches.snippet_extension` value in the track's `config.json` file
 
 ### Rule: exercises/{concept|practice}/<slug>/.articles/config.json is valid
 

building/tracks/approaches.md

@@ -42,3 +42,7 @@ If you'd like to compare different approaches, please write an [articles](/docs/
 In general, [Practice Exercises](/docs/building/tracks/practice-exercises) are more suitable to write approaches for, as they usually can be solved in multiple ways.
 
 For [Concept Exercises](/docs/building/tracks/concept-exercises), discussing the exemplar approach might be interesting. For example, you could show how the concept being taught makes certain code easier to write.
+
+## Configuring
+
+Make sure to set the `approaches.snippet_extension` field in your [track's `config.json` file](/docs/building/tracks/config-json).

building/tracks/config-json.md

@@ -28,6 +28,8 @@ The following top-level properties contain general track metadata:
   - `editor`: additional read-only editor file(s) patterns (optional)
 - `test_runner`: an object describing the track's test runner (if any): (required if `status.test_runner` is `true`)
   - `average_run_time`: a `number` value for the number of seconds the test runner takes on average to run, rounded to one decimal point precision (e.g. `1.8`) (required if `status.test_runner` is `true`)
+- `approaches`: an object with metadata on the track's approaches: (required if the track has any approaches)
+  - `snippet_extension`: a string value used for the snippet file's extension (e.g. `rb`) (required if the track has any approaches)
 
 ### Files
 
@@ -70,6 +72,9 @@ Support will be added to [configlet](/docs/building/configlet) to use these patt
   },
   "test_runner": {
     "average_run_time": 2.3
+  },
+  "approaches": {
+    "snippet_extension": "cs"
   }
 }
 ```