Copy this file to adr-<topic>-<n>.md (ADR-decision-records-1: one to three
lowercase words and the topic’s next number), fill every section, delete these
italic notes.
The title is the answer, not the topic: “A list has no +”, not “Operators on
lists”.
Status: Accepted | Open
Date:
There is no Built: line and no target version: whether a decision is built is
the index’s Built column, and when it was built is the CHANGELOG’s. The
record states the decision as it stands today. When a later decision changes
one of its rules, that rule is rewritten in place to say what holds now, with a
one-line note under it naming the decision that changed it (see the
index).
One question, in a sentence a reader can answer yes/no or pick from a list. Then: what is blocked without an answer, and why this question has to be decided here rather than defaulting. If it is really two questions, write two records.
What other languages and tools do about this same question, so the decision is made knowing the field and not in a vacuum. At least two, from different families where they exist (a systems language, a managed one, a functional one, the tool people already use). For each:
| Language / tool | Its answer | What it costs there | Source |
|---|---|---|---|
| link, version, or “from memory, not checked” |
Say what does not transfer and why (a garbage collector, a different ownership model, an ecosystem we do not have). Mark anything not verified; do not present recollection as fact.
Every option the field or the team suggests, including doing nothing. For each: what it is, one concrete example of the source a developer writes, then how it fares against the four weights of ADR-258. Fill the table with answers, not adjectives: who pays, what is written, what it costs at run time, how it reads next to a neighbouring rule.
// the code a developer writes under this option| D1 the special case pays, not the common one | D2 the compiler works, not the developer | D3 no cost for the common case | D4 consistent with itself | If it is wrong | |
|---|---|---|---|---|---|
| A | what it costs to undo, and who notices | ||||
| B |
Where a number decided it (an instruction count, a size, a latency), give that number and link the measurement; the method, the machine and any other figures live in the notes, not here. Where two weights pull apart, say so and say which one the language’s promise to the program (D1, D3) or to the reader (D2, D4) is being traded for.
The chosen option, stated as rules a reader can apply, each numbered (D1, D2, …) so that later records and code can cite one. Say which weight decided where the table did not. Say in a sentence why each rejected option lost. A rule a later decision changed reads as it holds now, with its note:
Changed by ADR-MMM Dn. (only when it was; otherwise leave it out)
What changes for a reader of the specification, for a program, for the compiler: stated as what is now true or now costs more, not as a to-do list. Link the issue(s) that carry the work; do not report their progress. Name the cost this decision accepts.
Questions the decision leaves open on purpose, each with where it will be asked
(an issue; one for the owner is labelled decision). Leave the section out if there are
none.
git log.Before marking a record Accepted: can a reader who has never seen this project answer “why is it this way, and what else could it have been”? If a sentence only makes sense to someone who watched the work happen, cut it.