REG-READER: computed-key registrar writes and their readers in --for

changelog.d/reg-reader.md

@@ -0,0 +1,5 @@
+### Added — `--for` table rows: a write into a registry with a computed key, and the reads of that registry
+
+A `shape="table"` site can now be a write into a table with a computed key: `storage[resource+"/log"] = podStorage.Log` in Go, `handlers[name + "_svc"] = handler` in Python, ``table[`/api/${ver}`] = route`` in TypeScript. The row is listed when the hit is the key or the value of that one statement (not the table's own name, and not a later statement on the line) and the enclosing function is named `New*`, `new_*`, `Register*` or `register_*` (an `async_` prefix aside). The name is the evidence, not proof. Such a row carries `reg=` with the table and key up to the `=`, and it is a strong row, so a task with no table or registration word lists it too. A literal key (`storage["pods"] = x`, `handlers[0x10] = f`, `handlers[1_000] = f`) is left to the table rule as before, and so are a comparison (`storage[k] == x`), a line of a multi-line string that looks like a write, and a write in a function with any other name.
+
+When the answer above the block already names that table, the element also lists `<lr>` rows: reads of the table in the row's file and in the files of the function's callers. A read is `t[k]` that is not the left side of an `=`, or `t.get(`, in code: a read inside a comment or a string is not counted. Each read on a line counts. A local bound to the function's call (`s := p.NewRESTStorage()`, `const routes = registerRoutes(...)`) counts as the same table, in the row's own file as in a caller's; the call has to be the value itself, so `s := choose(p.NewRESTStorage())` binds nothing. Reads whose key shares a quoted part of the written key come first, and at most 2 are listed. `readers=` counts all the reads found. It is a floor, with `floor="1"`, when a file could not be read, when callers in more than 16 files were not read, or when no call graph was there to find them. When the `<lr>` rows would push the element past the table's byte cap they are left out, and `readers=` still counts every read. A read of a same-named table in a file that does not call the function is not listed. Where the answer does not name the table, there are no `<lr>` rows and the element is unchanged. A legend sentence rides only with a subscript row. Gate: `test/forregrowcheck.sh` (the subscript-write and table-reader arms).

docs/LIMITS.md

@@ -546,6 +546,8 @@ Discloses: `capped`, `lit_capped`
 | `kForTableContextRows` | `4` | — | shape=table: table rows served with the lines after them |
 | `kForTableMaxAnchor` | `60` | — | a longer backticked span is no anchor |
 | `kForTableRankedRows` | `4096` | — | shape=table: source sites read for a table row and ordered (a registry past the readers in path order must still rank first) |
+| `kForTableReaderFiles` | `16` | — | REG-READER: caller files read for them, by path (past it: readers= is a floor) |
+| `kForTableReaderRows` | `2` | — | REG-READER: <lr> reads of a subscript row's table listed (readers= counts all) |
 | `kForTableRows` | `32` | — | shape=table: <ls> rows per anchor (next= lists all) |
 
 ### `src/formembers.h`