Struct SourceMapGenerator 

pub struct SourceMapGenerator { /* private fields */ }

Builder for creating source maps incrementally.

Register sources and names first (they return indices), then add mappings that reference those indices. Mappings should be added in generated-position order, though the builder does not require it.

Sources and names are automatically deduplicated.

Workflow

1. add_source — register each original file
2. set_source_content — optionally attach content
3. add_name — register identifier names
4. add_mapping / add_named_mapping — add mappings
5. to_json — serialize to JSON

Implementations

impl SourceMapGenerator

pub fn new(file: Option<String>) -> Self

Create a new empty source map generator.

pub fn set_source_root(&mut self, root: impl Into<String>)

Set the source root prefix.

pub fn set_debug_id(&mut self, id: impl Into<String>)

Set the debug ID (UUID) for this source map (ECMA-426).

pub fn set_scopes(&mut self, scopes: ScopeInfo)

Set scope and variable information (ECMA-426 scopes proposal).

pub fn set_assume_sorted(&mut self, sorted: bool)

Assume mappings are already sorted by (generated_line, generated_column).

When set to true, encode_mappings and to_decoded_map skip the sort step, avoiding both the O(n log n) sort and the Vec<&Mapping> allocation. Most bundlers add mappings in order, so this is a safe optimization in the common case.

pub fn add_source(&mut self, source: &str) -> u32

Register a source file and return its index.

pub fn set_source_content( &mut self, source_idx: u32, content: impl Into<String>, )

Set the content for a source file.

pub fn add_name(&mut self, name: &str) -> u32

Register a name and return its index.

pub fn add_to_ignore_list(&mut self, source_idx: u32)

Add a source index to the ignore list.

pub fn add_generated_mapping( &mut self, generated_line: u32, generated_column: u32, )

Add a mapping with no source information (generated-only).

pub fn add_mapping( &mut self, generated_line: u32, generated_column: u32, source: u32, original_line: u32, original_column: u32, )

Add a mapping from generated position to original position.

pub fn add_named_mapping( &mut self, generated_line: u32, generated_column: u32, source: u32, original_line: u32, original_column: u32, name: u32, )

Add a mapping with a name.

pub fn add_range_mapping( &mut self, generated_line: u32, generated_column: u32, source: u32, original_line: u32, original_column: u32, )

Add a range mapping from generated position to original position.

A range mapping maps every position from its generated position up to (but not including) the next mapping, applying a proportional delta to the original position (ECMA-426 rangeMappings proposal).

pub fn add_named_range_mapping( &mut self, generated_line: u32, generated_column: u32, source: u32, original_line: u32, original_column: u32, name: u32, )

Add a named range mapping.

pub fn maybe_add_mapping( &mut self, generated_line: u32, generated_column: u32, source: u32, original_line: u32, original_column: u32, ) -> bool

Add a mapping only if it differs from the previous mapping on the same line.

This skips redundant mappings where the source position is identical to the last mapping, which reduces output size without losing information. Used by bundlers and minifiers to avoid bloating source maps.

pub fn to_json(&self) -> String

Generate the source map as a JSON string.

pub fn mapping_count(&self) -> usize

Get the number of mappings.

pub fn to_decoded_map(&self) -> SourceMap

Directly construct a SourceMap from the generator’s internal state.

This avoids the encode-then-decode round-trip (VLQ encode to JSON string, then re-parse) that would otherwise be needed in composition pipelines.

Trait Implementations

impl Debug for SourceMapGenerator

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.