Add test generator by keiravillekode · Pull Request #380 · exercism/d

keiravillekode · 2026-09-28T03:39:44Z

The generator is implemented in Python and modelled on the x86-64-assembly track's generator.

It keeps the stub in source/*.d and replaces everything from the unittest line onwards.

It uses .meta/additional-test-cases.json if the file exists.

Generators are added for

all-your-base
game-of-life
isbn-verifier
largest-series-product
matrix
phone-number

The generated tests are identical to the existing tests.

Python style is enforced by ruff, run by pre-commit and a new pre-commit workflow.

Upgrade workflows to ubuntu-26.04.

Sync .gitignore from generic-track.

I used Claude for this PR.

The generator is implemented in Python and modelled on the x86-64-assembly track's generator. It keeps the stub in source/*.d and replaces everything from the `unittest` line onwards. It uses `.meta/additional-test-cases.json` if the file exists. Generators are added for - all-your-base - game-of-life - isbn-verifier - largest-series-product - matrix - phone-number The generated tests are identical to the existing tests. Python style is enforced by ruff, run by pre-commit and a new pre-commit workflow. Upgrade workflows to ubuntu-26.04. Sync .gitignore from generic-track. I used Claude for this PR.

github-actions · 2026-09-28T03:39:55Z

Hello 👋 Thanks for your PR.

This repo does not currently have dedicated maintainers. Our cross-track maintainers team will attempt to review and merge your PR, but it will likely take longer for your PR to be reviewed.

If you enjoy contributing to Exercism and have a track-record of doing so successfully, you might like to become an Exercism maintainer for this track.

Please feel free to ask any questions, or chat to us about anything to do with this PR or the reviewing process on the Exercism forum.

(cc @exercism/cross-track-maintainers)

IsaacG · 2026-09-28T03:45:15Z

+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1
+      - uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97
+        with:
+          python-version: "3.12"


Is this the default on Ubuntu 26? It seems old.

The first draft of the file had Ubuntu 24. Yes it is the default there (Python 3.12.3).

(My desktop is also Ubuntu 24 with Python 3.12.3.)

IsaacG · 2026-09-28T03:47:04Z

+        with:
+          python-version: "3.12"
+      - name: Set PY
+        run: echo "PY=$(python -VV | sha256sum | cut -d' ' -f1)" >> "$GITHUB_ENV"


What's the purpose of the hash here? Is the Python version set by hah and not version string?

This was in ahans' exercism/arm64-assembly#158 and I had never looked into it. Turns out it is a key for the cache, but we can remove these lines.

IsaacG · 2026-09-28T03:48:26Z

 - Create the test suite in $(jq -r '.test' <<< "${files}")
  - The tests should be based on the canonical data at 'https://github.com/exercism/problem-specifications/blob/main/exercises/${slug}/canonical-data.json'
  - Any test cases you don't implement, mark them in 'exercises/practice/${slug}/.meta/tests.toml' with "include = false"
+  - The tests can be generated by adding 'generators/exercises/${slug//-/_}.py' and running 'bin/generate ${slug}'


Would it make more sense to move this into .meta?

IsaacG · 2026-09-28T03:48:48Z

+# Example generating every exercise that has a generator:
+# bin/generate --all
+
+set -euo pipefail


Does this wrapper add any value?

Removed.

Lean's wrapper does add value. I never gained muscle memory without it.

Yesterday it would have been nice to have

bin/configlet sync -u -e list-ops bin/generate list-ops bin/verify-exercises-in-docker list-ops

in every track.

IsaacG · 2026-09-28T04:07:46Z

+def generated_slugs() -> list[str]:
+    return sorted(
+        path.stem.replace("_", "-")
+        for path in GENERATORS.glob("*.py")


Wouldn't the filename match the exercise name?

IsaacG · 2026-09-28T04:09:39Z

+    for slug in slugs:
+        try:
+            generate(slug, specifications)
+        except GeneratorError as error:


Should the generator continue on error?

We now stop.

If a file was missing or the exercise stub was empty, we print an error message.

If an exception occurs in an exercise .meta/slug.py, it presumably won't be any of FileNotFoundError, EOFError, subprocess.CalledProcessError. We don't catch the error, and Python prints a stack trace.

IsaacG · 2026-09-28T04:10:32Z

+    for char in value:
+        if char in _ESCAPES:
+            chars.append(_ESCAPES[char])
+        elif ord(char) < 0x20 or ord(char) == 0x7F:


Can this use the printable test?

IsaacG · 2026-09-28T04:11:31Z

+
+def d_int(value: int) -> str:
+    """Render an integer as a D integer literal."""
+    if isinstance(value, bool) or not isinstance(value, int):


Why is this test needed? The string function doesn't do type validation

IsaacG · 2026-09-28T05:24:44Z

+    rev: v6.0.0
+    hooks:
+    -   id: trailing-whitespace
+    -   id: end-of-file-fixer


Some of these checks (especially end-of-file) would be good to use widely. These might be nice to add to the generic-track* repos :D

My impression was that the generic-* repos essentially never change, but now I notice you have merged to generic-test-runner every few months. Should I have created a PR when I noticed https://forum.exercism.org/t/dependabot-frequency/53725 ?

Yes please. We clone those for each new track. If we keep those up to date and shiny, new tracks start off with the latest and greatest tooling we have!

IsaacG · 2026-09-28T15:47:14Z

@@ -0,0 +1,14 @@
+from lib import assert_eq, d_array, d_inline_array


Out of curiosity, is there a reason you didn't want to use templates?

If these files live in .meta, would it make sense for them to use a standard filename, eg test_generator.py, similar to the other meta files?

I have never been a big user of templates, for example my first web development was with Java servlets and I never bothered with JSP. I can read and write without templates more easily than with templates

Now using test_generator.py

IsaacG · 2026-09-28T15:49:33Z

+def flatten(cases: list[Case], parents: tuple[str, ...] = ()) -> list[Case]:
+    """Flatten nested groups, recording the descriptions of enclosing groups."""
+    flattened = []
+    for case in cases:
+        if "cases" in case:
+            description = case.get("description")
+            nested = (*parents, description) if description else parents
+            flattened.extend(flatten(case["cases"], nested))


Suggested change

def flatten(cases: list[Case], parents: tuple[str, ...] = ()) -> list[Case]:

"""Flatten nested groups, recording the descriptions of enclosing groups."""

flattened = []

for case in cases:

if "cases" in case:

description = case.get("description")

nested = (*parents, description) if description else parents

flattened.extend(flatten(case["cases"], nested))

def flatten(cases: list[Case], parents: list[str] | None = None) -> list[Case]:

"""Flatten nested groups, recording the descriptions of enclosing groups."""

flattened = []

if parents is None:

parents = []

for case in cases:

if "cases" in case:

description = case.get("description")

nested = parents + [description] if description else parents

flattened.extend(flatten(case["cases"], nested))

IsaacG · 2026-09-28T15:51:34Z

+    # Avoid leaving __pycache__ in the exercise directory.
+    sys.dont_write_bytecode = True


This should probably either go at the top of the file or, if you want to localize the change, be reset.

IsaacG · 2026-09-28T15:59:32Z

+        raise EOFError(f"{path.relative_to(ROOT)} is empty; create the stub first")
+    match = re.search(r"^unittest\b", content, flags=re.MULTILINE)
+    if match:
+        return content[: match.start()]


Suggested change

return content[: match.start()]

return content[:match.start()]

Make spacing consistent with describe()

ruff format demands that space and puts it back.

But it's fine with description[:1].upper() on line 114? That's odd. But probably not worth fighting ruff over.

IsaacG · 2026-09-28T16:24:37Z

+    "\n": "\\n",
+    "\r": "\\r",
+    "\t": "\\t",
+    "\0": "\\0",


I suspect there's no NULL or CR chars in any of the exercises, but I suppose it doesn't hurt to have these.

IsaacG · 2026-09-28T16:25:38Z

+    rev: v6.0.0
+    hooks:
+    -   id: trailing-whitespace
+    -   id: end-of-file-fixer


Yes please. We clone those for each new track. If we keep those up to date and shiny, new tracks start off with the latest and greatest tooling we have!

IsaacG · 2026-09-28T16:27:11Z

+    rev: v0.16.9
+    hooks:
+    -   id: ruff-check
+        args: [--fix, --target-version, py314]


I'm a bit surprised ruff doesn't pick up the system version 🤷‍♂️ We could also drop a .ruff.toml config file to move the version from the workflow file to the repo "main" content.

Adding a .ruff.toml config file

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

exercism-i18n · 2026-09-28T23:14:37Z

This PR has been translated 🚀

keiravillekode requested a review from IsaacG September 28, 2026 03:39

IsaacG reviewed Sep 28, 2026

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test with ldc-1.43.0

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IsaacG reviewed Sep 28, 2026

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Comment thread .pre-commit-config.yaml

keiravillekode added 3 commits September 28, 2026 14:49

python-version 3.14.4

57af4f0

simplify .github/workflows/pre-commit.yml

8747ab2

python-version 3.14

b75e2eb

IsaacG reviewed Sep 28, 2026

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Comment thread .github/workflows/pre-commit.yml Outdated

IsaacG reviewed Sep 28, 2026

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keiravillekode added 8 commits September 28, 2026 16:46

exercises/practice/slug/.meta/slug.py

bcfa5aa

textwrap.indent

4df50bd

import tomllib early

76d31aa

import pathlib

deb11a3

subprocess.check_output()

8df8827

retire GeneratorError

b17f5c5

EOFError

cccb704

pre-commit workflow omits python-version

d47e930

IsaacG approved these changes Sep 28, 2026

View reviewed changes

test_generator.py

5961082

keiravillekode added the ready-to-translate The English in this PR is final; queue its translations label Sep 28, 2026

exercism-i18n Bot mentioned this pull request Sep 28, 2026

Translate exercism/d#380: Add test generator exercism/i18n#161

Closed

exercism-i18n Bot added a commit to exercism/i18n that referenced this pull request Sep 28, 2026

Translate exercism/d#380: 54 item(s)

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Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

keiravillekode merged commit 3d6eeb5 into exercism:main Sep 28, 2026
13 of 14 checks passed

keiravillekode deleted the generators-generate branch September 28, 2026 23:16

		@@ -0,0 +1,14 @@
		from lib import assert_eq, d_array, d_inline_array

		# Avoid leaving __pycache__ in the exercise directory.
		sys.dont_write_bytecode = True

	return content[: match.start()]
	return content[:match.start()]

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