Errors

Updated Nov 1, 2026

Textlane raises textlane.TextlaneError, whose code names what went wrong, so a caller can tell the cases apart without reading the message:

import textlane

code = ""
try:
    textlane.textlane().use("md.nope")
except textlane.TextlaneError as error:
    code = error.code
code
# unknown-plugin

Code	When
`unknown-plugin`	`use` names a plugin textlane does not have
`invalid-plugin`	`use` gets something that is neither a plugin, a list nor a preset
`invalid-options`	a plugin's options do not match its types, when the pipeline is built
`frozen-processor`	`use` or a `data` setter is called on a frozen processor
`missing-parser`	`parse` or `process` runs with no parser in the pipeline
`missing-compiler`	`stringify` or `process` runs with no compiler in the pipeline
`invalid-stage`	a stage gets a tree it does not take, such as hast before `md.to_html`
`async-in-sync`	`process` or `run` meets a stage with asynchronous work
`invalid-tree`	a tree given to `run` or `stringify` is not valid unist
`unsupported-node`	a tree given to `run` or `stringify` holds a node with no `type`
`unknown-node`	a compiler meets a node type it cannot write
`tree-too-deep`	a tree nests too deep to pass between Rust and Python
`mdx-failed`	`mdx.compile` meets JavaScript it cannot compile
`unsafe-number`	`nl.indefinite_article` meets a number too large to read
`highlight-failed`	`html.highlight` cannot color a code block
`highlight-unavailable`	`html.highlight`'s grammars and themes failed to load

Syntax errors in MDX carry the upstream's source and rule as their code, as micromark-extension-mdx-expression:acorn for an expression that does not parse.

Options are checked when the pipeline is built, the first time it runs or freezes, not when use is called.