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7c873ca615
Adds configurable parser modes to std/parseopt module. **Take two.**
Initially solved the issue of not being able to pass arguments to short
options as you do with most everyday CLI programs, but reading the tests
made me add more features so that some of the behaviour could be changed
and here we are.
**`std/parseopt` now supports three parser modes** via an optional
`mode` parameter in `initOptParser` and `getopt`.
Three modes are provided:
- `NimMode` (default, fully backward compatible),
- `LaxMode` (POSIX-inspired with relaxed short option handling),
- `GnuMode` (stricter GNU-style conventions).
The new modes are marked as experimental in the documentation.
The parser behaviour is controlled by a new `ParserRules` enum, which
provides granular feature flags that modes are built from. This makes it
possible for users with specific requirements to define custom rule sets
by importing private symbols, this is mentioned but clearly marked as
unsupported.
**Backward compatibility:**
The default mode preserves existing behaviour completely, with a single
exception: `allowWhitespaceAfterColon` is deprecated.
Now, `allowWhitespaceAfterColon` doesn't make much sense as a single
tuning knob. The `ParserRule.prSepAllowDelimAfter` controls this now.
As `allowWhitespaceAfterColon` had a default, most calls never mention
it so they will silently migrate to the new `initOptParser` overload. To
cover cases when the proc param was used at call-site, I added an
overload, which modifies the default parser mode to reflect the required
`allowWhitespaceAfterColon` value. Should be all smooth for most users,
except the deprecation warning.
The only thing I think can be classified as the breaking change is a
surprising **bug** of the old parser:
```nim
let p = initOptParser("-n 10 -m20 -k= 30 -40", shortNoVal = {'v'})
# ^-disappears
```
This is with the aforementioned `allowWhitespaceAfterColon` being true
by default, of course. In this case the `30` token is skipped
completely. I don't think that's right, so it's fixed.
Things I still don't like about how the old parser and the new default
mode behave:
1. **Parser behaviour is controlled by an emptiness of two containers**.
This is an interesting approach. It's also made more interesting because
the `shortNoVal`/`longNoVal` control both the namesakes, but *and also
how their opposites (value-taking opts) work*.
---
**Edit:**
2. `shortNoVal` is not mandatory:
```nim
let p = initOptParser(@["-a=foo"], shortNoVal = {'a'})
# Nim, Lax parses as: (cmdShortOption, "a", "foo")
# GnuMode parses as: (cmdShortOption, "a", "=foo")
```
In this case, even though the user specified `a` as no no-val, parser
ignores it, relying only on the syntax to decide the kind of the
argument. This is especially problematic with the modes that don't use
the rule `prShortAllowSep` (GnuMode), in this case the provided input is
twice invalid, regardless of the `shortNoVal`.
With the current parser architecture, parsing it this way **is
inevitable**, though. We don't have any way to signal the error state
detected with the input, so the user is expected to validate the input
for mistakes.
Bundling positional arguments is nonsensical and short option can't use
the separator character, so `[cmd "a", arg "=foo"]` and `[cmd "a", cmd
"=", cmd "f"...]` are both out of the question **and** would complicate
validating, requiring keeping track of a previous argument. Hope I'm
clear enough on the issue.
**Future work:**
1. Looks like the new modes are already usable, but from the discussions
elsewhere it looks like we might want to support special-casing
multi-digit short options (`-XX..`) to allow numerical options greater
than 9. This complicates bundling, though, so requires a bit of thinking
through.
2. Signaling error state?
---------
Co-authored-by: Andreas Rumpf <araq4k@proton.me>