Errors

Updated Nov 1, 2026

Every fallible call returns textlane::Error, with a code naming what went wrong and a message for people; it implements std::error::Error.

use textlane::Pipeline;

let error = Pipeline::new()
    .use_value(&serde_json::json!("md.nope"), None)
    .err()
    .ok_or("no error")?;
error.code
// unknown-plugin

Code	When
`invalid-stage`	`freeze` finds a stage that does not take the tree the one before returns
`missing-parser`	`parse` runs with no parser in the processor
`async-in-sync`	`run_sync` meets a stage with asynchronous work
`unknown-node`	a compiler meets a node type it cannot write
`mdx-failed`	`mdx::Compile` meets JavaScript it cannot compile
`unsafe-number`	`nl::IndefiniteArticle` 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
`missing-natural-language-parser`	`html::ToNaturalLanguage` runs in a build without the `nl` feature

Pipeline adds the codes of unified's API, as the Node.js and Python packages raise them:

Code	When
`unknown-plugin`	`use_value` names a plugin textlane does not have
`invalid-plugin`	`use_value` 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 freezes
`invalid-data`	`replace_data` gets something that is not an object
`frozen-processor`	`use_value` or a data setter is called on a frozen pipeline
`missing-compiler`	`stringify` or `process` runs with no compiler in the pipeline
`invalid-tree`	a JSON tree is not valid unist
`unsupported-node`	a JSON tree holds a node with no `type`
`tree-too-deep`	a tree nests too deep to write as JSON

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.