Enhancement-883: an unknown integration method is named, and so is the method that runs instead — method=trbdf ran trap after "unsupported integration method"

Enhancement-883: an unknown integration method is named, and so is the method that runs instead — method=trbdf ran trap after "unsupported integration method"

Scope: D3 of the
transient stress campaign of 2026-10-12.

ngspice: spicelib/analysis/cktsopt.c, CKTsetOpt: OPT_METHOD with a name it does not know
warns and keeps the current method, instead of returning E_METHOD.

examples/transopts_examples/ (new, shared with E-881 and
E-882). ngspice only.

Suites:

• transopts_examples: [6] is this enhancement's, 7 of 7 per
  solver. On the E-875 binaries [6] fails.
• The full sweep: 585 of 585.

What was wrong

.option method=trbdf, a typo for trbdf2, printed

setAnalysisParm(options) ci_curOpt: unsupported integration method

and the run went on with trap. The message named neither the value nor the method that ran.
method=bdf and method=gear2 did the same.

The change

An unknown name is reported with the value, the names that exist and the method that is kept:

Warning -- Option method = trbdf is unknown (use trap, gear, trbdf2, sdirk or adams); ignored, keeping trap

After an option method=gear, an unknown name says keeping gear. The generic line is no longer
printed.

The checks

transopts_examples:

• [6] method=trbdf names the value and the valid ones, and says trap is kept. After
  option method=gear, method=foo says gear is kept. The generic "unsupported integration
  method" line is gone.

Write-up: enhancements_doc/Enhancement-883.md