A script whose first lines name an engine with `#targetengine name` (or
`//@targetengine name`) runs in that engine, and a later script that names
it sees the globals and functions earlier runs left, until the engine is
dropped or the session ends. A script without the line, and
`#targetengine main`, still get a new engine for each run.
- A session keeps at most 8 named engines, each with a 64 MiB heap. A run
that goes past the heap ends with the heap limit, and the engine stays
usable. Names are 1 to 64 bytes. The line comes once, in the script
itself, before its code and its #include lines.
- An uncaught error, a limit or script.stop puts the documents back and
keeps the globals the run set. An internal error drops the engine. A run
stopped at a dialog or left paused ends where it was before the engine
is kept. An error in a function an earlier run defined is reported
without a line and column.
- `vc`, `$`, `alert`, `confirm` and `prompt` are made once for each engine
and act for the run that calls them, including copies an earlier run kept
in a global. `vc.args` gives a read-only copy of the calling run's
`args`, and what a run sets on `$` lasts for that run only.
- `script.engines` lists the named engines with their heap, and
`script.engine.drop {name}` drops one. Scripts cannot run either.
- The engines stay on the thread that made them. A session used on
another thread starts there with no named engines, and the old ones are
dropped on their own thread.
- The web build has no named engines: a run that names one other than
`main` ends with an error before any of it runs.
- `Realm::end` ends a run where it is, `Realm::error_source` counts from
the realm's last script, and `HostItem::FrozenGetter` gives a frozen
value each time it is read.
- The script checker lists `#targetengine` as a supported directive.
Docs: docs/mcp.md, docs/target-app-parity.md, docs/gaps.md.
An error a finally block passed on unchanged was reported at the end of
that block, in script.run's report and in the Script Console, because the
block's end raised the error again at a new site. The interpreter now keeps
the site of the exception each finally block runs for, keyed by the stack
slot that holds it, and the block's end throws the exception on from that
site. This holds through nested finally blocks, called functions, resumed
runs and marked host errors. An error the finally block throws is reported
at that throw, and one its return, break or continue discards is not
reported.
A failure $.evalFile raised for a file it could not run was placed by
matching the uncaught error's message against the last such failure. A
script that caught the failure and threw it again later, or threw a new
error whose message held its text, was reported at the failed file's line
instead of the second throw.
The failure now carries a mark (HostError::Marked) with the exception.
A catch clause drops the mark, a throw raises the value without one, and
a finally block that ends normally throws it on with its mark, nested
finally blocks included. Realm::error_mark gives the mark of the error a
run ended with, and the engine looks up the file, line and column by it.
`#strict on` and `//@strict on` no longer end the run as unsupported. They
turn on the checks the dollar-object help page gives for `$.strict`
(https://extendscript.docsforadobe.dev/extendscript-tools-features/dollar-object/):
an assignment to a read-only property throws a TypeError, and so does a new
property on an object that takes none.
VectorCraft's own rules: a getter-only property counts as read-only; the
objects that take no new properties are the non-extensible ones
(preventExtensions, seal, freeze, and the frozen vc and $ objects); the last
`#strict` line of the script and its includes sets the whole run, and runs
without one are unchanged; eval and Function take the checks of the code
that compiles them; a file $.evalFile runs keeps its own line's checks for
its code and functions, or takes the caller's without one. The rest of ES5
strict mode stays with 'use strict'.
The js crate carries the setting per compiled source
(Realm::set_strict_writes, and a strict_writes callback on
HostItem::Evaluator), and applies it only to property assignments.
Before a script runs, `script.run` reads its preprocessor lines (`#` or
`//@` at the start of a line, outside strings and comments):
- `#include` and `//@include` put another file's text in place of the
line, looked for beside the including file, then in each
`#includepath` folder, then in each `JSINCLUDE` folder. A later
`#includepath` replaces the list.
- `#script` names the run unless `name` is given; `#target` takes any
value; `#strict off` is taken. `#strict on`, `#targetengine` and
`#engine` are refused as unsupported, and any other `#name` as
unknown.
`$.evalFile(path, timeout?)` runs a file in the same global environment
and returns its last value, `$.fileName` is the file being run and
`$.includePath` the include folders.
A script run from a file reads these files only in its folder and the
folders below it. Paths with a `..` name, links or junctions that lead
out, device names, streams and network paths are refused; a script
given as text reads none. A run reads at most 64 files 16 levels deep,
32 MiB of source in all and 1,024 paths looked up. An error in an
included or evaluated file is reported at that file's line and column,
and the report's new `file` field names it.
Docs: docs/mcp.md (script.run, Script Console), docs/target-app-parity.md.
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