2026-11-06 05:53:53 +01:00
12 changed files with 334 additions and 1 deletions
@@ -45,6 +45,14 @@ Each lecture has its own screenshot in `docs/images/` (made by `docs/images/capt

 ![Lecture 4: __name__ and __main__](docs/images/lecture-04.png)

+**Lecture 5: functions are first-class objects.** A function can be passed as an argument (`calculate(add, 2, 3)`), defined inside another function and returned from it. See `flask_day_54.domain.first_class_functions`; run it with `python -m flask_day_54.domain.first_class_functions`.
+
+![Lecture 5: functions as first-class objects](docs/images/lecture-05.png)
+
+**Lecture 6: decorators and the `@` syntax.** `@make_bold` above a function is shorthand for `say_hello = make_bold(say_hello)`. See `flask_day_54.domain.decorators`; run it with `python -m flask_day_54.domain.decorators`.
+
+![Lecture 6: decorators](docs/images/lecture-06.png)
+
 ## 📋 Requirements

 - Python 3.13 or newer, because the project sets `requires-python = ">=3.13"` in `pyproject.toml`.
@@ -18,7 +18,7 @@ document of a type. `Primary File` may contain a glob (e.g.
 | ADR | Architecture Decision Record | docs/adr/adr-NNNN-*.md | 0002 |
 | DICT | Domain Dictionary | docs/dictionary.md | 002 |
 | TM | Traceability Matrix | docs/sqa/traceability-matrix.md | 002 |
-| RC | SQA Review Record | docs/sqa/reviews/rc-*.md | 018 |
+| RC | SQA Review Record | docs/sqa/reviews/rc-*.md | 019 |

 ## Languages

@@ -0,0 +1,10 @@
+<!doctype html><meta charset='utf-8'><style>
+body{margin:0;background:#1e1e1e;font-family:Consolas,'DejaVu Sans Mono',monospace;color:#d4d4d4}
+.bar{background:#333;color:#ccc;padding:8px 14px;font-size:14px}
+pre{margin:0;padding:16px 18px;font-size:15px;line-height:1.45;white-space:pre-wrap}
+.p{color:#6a9955}.c{color:#9cdcfe}
+</style><div class='bar'>Terminal - lecture 5: functions as first-class objects</div><pre><span class="p">$</span> <span class="c">python -m flask_day_54.domain.first_class_functions</span>
+calculate(add, 2, 3) = 5
+calculate(subtract, 5, 3) = 2
+outer_function() = Hello from the nested function
+returned nested function() = Hello from the nested function</pre>
@@ -0,0 +1,10 @@
+<!doctype html><meta charset='utf-8'><style>
+body{margin:0;background:#1e1e1e;font-family:Consolas,'DejaVu Sans Mono',monospace;color:#d4d4d4}
+.bar{background:#333;color:#ccc;padding:8px 14px;font-size:14px}
+pre{margin:0;padding:16px 18px;font-size:15px;line-height:1.45;white-space:pre-wrap}
+.p{color:#6a9955}.c{color:#9cdcfe}
+</style><div class='bar'>Terminal - lecture 6: decorators and the @ syntax</div><pre><span class="p">$</span> <span class="c">python -m flask_day_54.domain.decorators</span>
+plain: Hello, World!
+by hand, make_bold(plain_hello)(): &lt;b&gt;Hello, World!&lt;/b&gt;
+@ syntax, say_hello(): &lt;b&gt;&lt;em&gt;&lt;u&gt;Hello, World!&lt;/u&gt;&lt;/em&gt;&lt;/b&gt;
+say_hello.__name__: say_hello</pre>
@@ -0,0 +1,62 @@
+# Review of MIL-004
+
+## Metadata
+| Key | Value |
+| --- | --- |
+| ID | RC-018 |
+| CrossReference | [MIL-004], [QC-PY-001] |
+
+## Version History
+| Date | Status | Author | Reviewer | Change | Commit |
+| --- | --- | --- | --- | --- | --- |
+| 2026-11-06 | Proposed | Jens Tirsvad Nielsen | AI as stand-in for S01 | Initial version | [6dac2be] |
+
+---
+
+## Artifact Under Review
+
+- Instance reviewed: [MIL-004]
+- Checklist used: [QC-PY-001]
+- Scope: full review of the source and tests delivered by MIL-004 (src/, tests/)
+- Language and domain: n/a
+- Language reviewer: none (the reviewer reads English and knows the IT domain)
+- Mode: autonomous, not independent (AI as stand-in for S01)
+
+## Checklist Results
+
+| # | Criterion | Status | Evidence/Notes |
+| --- | --- | --- | --- |
+| 1 | Packages, modules, functions, variables, classes and constants follow PEP 8 casing (`snake_case`, `PascalCase`, `UPPER_SNAKE`) | Pass | Modules, functions and constants use snake_case / UPPER_SNAKE; classes none or PascalCase. |
+| 2 | Names state purpose in the domain's language; no unexplained abbreviations, no single-letter names outside tiny scopes | Pass | Names follow the lecture and the domain dictionary. |
+| 3 | Code is produced by the project's formatter and passes its linter with no unexplained suppressions | Pass | `ruff format` leaves files unchanged and `ruff check` (E, F, I, B, UP) passes; configured in pyproject.toml. |
+| 4 | Every function and method signature is type-annotated, including `-> None` | Pass | Every function signature is annotated, including `-> None`. |
+| 5 | No bare `except:`, no swallowed exceptions; specific exceptions are raised and the cause is kept (`raise ... from`) | Pass | No bare except and no swallowed exception. |
+| 6 | No mutable default arguments and no shadowed builtins | Pass | No mutable defaults; no builtin shadowed. |
+| 7 | Files, locks and connections are managed with context managers | N-A | No file, lock or connection is opened. |
+| 8 | Public modules, classes and functions have docstrings that say what, not how | Pass | Module and public names carry docstrings plus Doxygen comments. |
+| 9 | Logging uses `logging`, not `print`; no secrets or personal data in log output | N-A | Console output of the demo entry points (print under the __main__ guard) is the program's result, not diagnostic logging; no secrets handled. |
+| 10 | Classes and operations trace to the Design Class Diagram they implement; deviations are recorded | N-A | No DCD exists in this project; the layered layout is recorded in ADR-0001. |
+| 11 | Tests exist for new behaviour, are named for the behaviour, and do not depend on order or the network | Pass | pytest tests named for behaviour; no order or network dependence. |
+| 12 | Type checker runs in strict mode without errors; `Any` is justified in a comment | N-A | No type checker is configured (optional criterion). |
+| 13 | Dependencies are declared and pinned in the project's dependency file, none unused | Pass | Dependencies are declared in pyproject.toml; none unused (Flask is the optional `web` extra). |
+| 14 | Each piece of knowledge (a business rule, constant, format, validation or query) is defined in one place; code is merged only where it expresses the same knowledge, not where it merely looks alike | Pass | Each constant is defined once in the constants.py of its layer. |
+| 15 | Imports point inward: business-rule modules import no framework, database, UI or delivery-mechanism code, and there are no import cycles | Pass | `domain` imports no framework or outer layer; imports point inward; no cycles. |
+| 16 | SOLID holds: a class or module has one reason to change; new behaviour is added by extension, not by editing a type test in several places; subclasses honour the contract of their base; protocols are narrow; high-level code depends on protocols or abstract types and receives its implementations | Pass | Small modules with one reason to change; no type tests or subclass hierarchies. |
+| 17 | Source is laid out in the layers and folders of the clean architecture folder structure (`domain`, `application`, `infrastructure`, `presentation` packages under `src/`, and `unit`, `integration` and `e2e` under `tests/`), in `snake_case`, and imports between the layers point inward | Pass | Layers domain, application, infrastructure, presentation under src/flask_day_54; tests in unit and e2e (ADR-0001); no layer merged. |
+| 18 | File and folder names are English, contain no space and no character outside letters, digits, `-`, `_` and `.`, and follow the casing of the language for files | Pass | English snake_case file names without spaces. |
+
+## Overall Verdict
+
+Go — All applicable mandatory criteria pass.
+
+## Action Items
+
+| Action | Owner | Due |
+| --- | --- | --- |
+| None | S01 | - |
+
+---
+
+[MIL-004]: ../../milestones/mil-004-functions-decorators.md
+[QC-PY-001]: ../../../framework/qc/code/qc-programming-python.md
+[6dac2be]: https://git.tirsystem.com/Tirsvad-Udemy-100-days-of-code/054-flask/commit/6dac2be41a1857a8459520ece1f61c8683f79912
@@ -38,3 +38,26 @@ CLI_COMMANDS: Final[tuple[tuple[str, str, str, bool, str], ...]] = (
        NO_CONFIRMATION_WARNING,
    ),
 )
+
+## @brief Message returned by the nested function of lecture 5.
+NESTED_FUNCTION_MESSAGE: Final[str] = "Hello from the nested function"
+
+## @brief Demo line templates of lecture 5; `{value}` is the printed result.
+ADD_DEMO_LINE: Final[str] = "calculate(add, 2, 3) = {value}"
+SUBTRACT_DEMO_LINE: Final[str] = "calculate(subtract, 5, 3) = {value}"
+OUTER_DEMO_LINE: Final[str] = "outer_function() = {value}"
+RETURNED_DEMO_LINE: Final[str] = "returned nested function() = {value}"
+
+## @brief HTML tag names used by the lecture 6 decorators.
+BOLD_TAG: Final[str] = "b"
+EMPHASIS_TAG: Final[str] = "em"
+UNDERLINE_TAG: Final[str] = "u"
+
+## @brief Template wrapping text in an HTML tag.
+HTML_TAG_TEMPLATE: Final[str] = "<{tag}>{text}</{tag}>"
+
+## @brief Demo line templates of lecture 6; `{value}` is the printed result.
+PLAIN_DEMO_LINE: Final[str] = "plain: {value}"
+BY_HAND_DEMO_LINE: Final[str] = "by hand, make_bold(plain_hello)(): {value}"
+AT_SYNTAX_DEMO_LINE: Final[str] = "@ syntax, say_hello(): {value}"
+NAME_DEMO_LINE: Final[str] = "say_hello.__name__: {value}"
@@ -0,0 +1,69 @@
+## @file decorators.py
+#  @brief Lecture 6 demo of decorators and the `@` syntax.
+"""A decorator wraps a function to add behaviour without editing it."""
+
+from collections.abc import Callable
+from functools import wraps
+
+from flask_day_54.domain.constants import (
+    AT_SYNTAX_DEMO_LINE,
+    BOLD_TAG,
+    BY_HAND_DEMO_LINE,
+    EMPHASIS_TAG,
+    GREETING,
+    HTML_TAG_TEMPLATE,
+    NAME_DEMO_LINE,
+    PLAIN_DEMO_LINE,
+    UNDERLINE_TAG,
+)
+
+
+def _tag_decorator(tag: str) -> Callable[[Callable[[], str]], Callable[[], str]]:
+    """Build a decorator that wraps the returned text in the given HTML tag."""
+
+    def decorator(func: Callable[[], str]) -> Callable[[], str]:
+        @wraps(func)
+        def wrapper() -> str:
+            return HTML_TAG_TEMPLATE.format(tag=tag, text=func())
+
+        return wrapper
+
+    return decorator
+
+
+## @brief Wrap the text of a function in `<b>` tags.
+make_bold = _tag_decorator(BOLD_TAG)
+
+## @brief Wrap the text of a function in `<em>` tags.
+make_emphasis = _tag_decorator(EMPHASIS_TAG)
+
+## @brief Wrap the text of a function in `<u>` tags.
+make_underlined = _tag_decorator(UNDERLINE_TAG)
+
+
+## @brief Greeting with the three decorators stacked; the nearest applies first.
+@make_bold
+@make_emphasis
+@make_underlined
+def say_hello() -> str:
+    """Return the greeting."""
+    return GREETING
+
+
+## @brief The same greeting without any decorator.
+def plain_hello() -> str:
+    """Return the greeting."""
+    return GREETING
+
+
+## @brief Print the lecture 6 demo.
+def main() -> None:
+    """Print the plain, hand-decorated and `@` decorated greeting."""
+    print(PLAIN_DEMO_LINE.format(value=plain_hello()))
+    print(BY_HAND_DEMO_LINE.format(value=make_bold(plain_hello)()))
+    print(AT_SYNTAX_DEMO_LINE.format(value=say_hello()))
+    print(NAME_DEMO_LINE.format(value=say_hello.__name__))
+
+
+if __name__ == "__main__":
+    main()
@@ -0,0 +1,66 @@
+## @file first_class_functions.py
+#  @brief Lecture 5 demo of functions as first-class objects.
+"""Functions can be passed as arguments, nested and returned like any value."""
+
+from collections.abc import Callable
+
+from flask_day_54.domain.constants import (
+    ADD_DEMO_LINE,
+    NESTED_FUNCTION_MESSAGE,
+    OUTER_DEMO_LINE,
+    RETURNED_DEMO_LINE,
+    SUBTRACT_DEMO_LINE,
+)
+
+
+## @brief Add two numbers.
+def add(n1: float, n2: float) -> float:
+    """Return the sum of the two numbers."""
+    return n1 + n2
+
+
+## @brief Subtract the second number from the first.
+def subtract(n1: float, n2: float) -> float:
+    """Return the first number minus the second."""
+    return n1 - n2
+
+
+## @brief Apply a function passed as argument to two numbers.
+#  @param func The function to call with `n1` and `n2`.
+def calculate(n1: float, n2: float, func: Callable[[float, float], float]) -> float:
+    """Return `func(n1, n2)`."""
+    return func(n1, n2)
+
+
+## @brief Call a function that is defined inside this one.
+def outer_function() -> str:
+    """Return the result of the nested function, reachable only in here."""
+
+    def nested_function() -> str:
+        return NESTED_FUNCTION_MESSAGE
+
+    return nested_function()
+
+
+## @brief Hand the nested function to the caller.
+def returns_nested_function() -> Callable[[], str]:
+    """Return the nested function so it can be stored and called later."""
+
+    def nested_function() -> str:
+        return NESTED_FUNCTION_MESSAGE
+
+    return nested_function
+
+
+## @brief Print the lecture 5 demo.
+def main() -> None:
+    """Print the results of the first-class function examples."""
+    print(ADD_DEMO_LINE.format(value=calculate(2, 3, add)))
+    print(SUBTRACT_DEMO_LINE.format(value=calculate(5, 3, subtract)))
+    print(OUTER_DEMO_LINE.format(value=outer_function()))
+    stored = returns_nested_function()
+    print(RETURNED_DEMO_LINE.format(value=stored()))
+
+
+if __name__ == "__main__":
+    main()
@@ -0,0 +1,43 @@
+from collections.abc import Callable
+
+from flask_day_54.domain.decorators import (
+    make_bold,
+    make_emphasis,
+    make_underlined,
+    plain_hello,
+    say_hello,
+)
+
+
+def test_make_bold_wraps_text_in_b_tags() -> None:
+    assert make_bold(plain_hello)() == "<b>Hello, World!</b>"
+
+
+def test_make_emphasis_wraps_text_in_em_tags() -> None:
+    assert make_emphasis(plain_hello)() == "<em>Hello, World!</em>"
+
+
+def test_make_underlined_wraps_text_in_u_tags() -> None:
+    assert make_underlined(plain_hello)() == "<u>Hello, World!</u>"
+
+
+def test_say_hello_applies_stacked_decorators_nearest_first() -> None:
+    assert say_hello() == "<b><em><u>Hello, World!</u></em></b>"
+
+
+def test_plain_hello_is_not_decorated() -> None:
+    assert plain_hello() == "Hello, World!"
+
+
+def test_decorator_keeps_name_and_docstring_of_wrapped_function() -> None:
+    assert say_hello.__name__ == "say_hello"
+    assert say_hello.__doc__ == "Return the greeting."
+
+
+def test_decorator_wraps_function_returning_another_string() -> None:
+    def goodbye() -> str:
+        return "Bye"
+
+    decorated: Callable[[], str] = make_bold(goodbye)
+
+    assert decorated() == "<b>Bye</b>"
@@ -0,0 +1,42 @@
+from flask_day_54.domain import first_class_functions
+from flask_day_54.domain.first_class_functions import (
+    add,
+    calculate,
+    outer_function,
+    returns_nested_function,
+    subtract,
+)
+
+
+def test_add_returns_sum_of_two_numbers() -> None:
+    assert add(2, 3) == 5
+
+
+def test_subtract_returns_difference_of_two_numbers() -> None:
+    assert subtract(5, 3) == 2
+
+
+def test_calculate_applies_add_when_add_is_passed() -> None:
+    assert calculate(2, 3, add) == 5
+
+
+def test_calculate_applies_subtract_when_subtract_is_passed() -> None:
+    assert calculate(5, 3, subtract) == 2
+
+
+def test_calculate_applies_lambda_when_lambda_is_passed() -> None:
+    assert calculate(4, 3, lambda n1, n2: n1 * n2) == 12
+
+
+def test_outer_function_returns_nested_function_result() -> None:
+    assert outer_function() == "Hello from the nested function"
+
+
+def test_returned_nested_function_is_callable_independently() -> None:
+    stored = returns_nested_function()
+
+    assert stored() == "Hello from the nested function"
+
+
+def test_nested_function_is_not_a_module_attribute() -> None:
+    assert not hasattr(first_class_functions, "nested_function")