swc-project/swc · error

invalid name reference: {name_id}

Error message

invalid name reference: {name_id}

What it means

Same decoder loop as the source-index check, but for the optional 5th VLQ field: name_id accumulates deltas across segments and must remain within the `names` array bounds. When the accumulated name index >= names.len(), the mappings reference an original identifier name that does not exist in the `names` array, and decoding fails. The `names` array and `mappings` are out of sync.

Source

Thrown at crates/swc_config/src/source_map.rs:93

                            if nums.len() != 4 && nums.len() != 5 {
                                bail!(
                                    "invalid vlq segment size; expected 4 or 5, got {}",
                                    nums.len()
                                );
                            }
                            src_id = (i64::from(src_id) + nums[1]) as u32;
                            if src_id >= sources.len() as u32 {
                                bail!("invalid source reference: {src_id}");
                            }

                            src = src_id;
                            src_line = (i64::from(src_line) + nums[2]) as u32;
                            src_col = (i64::from(src_col) + nums[3]) as u32;

                            if nums.len() > 4 {
                                name_id = (i64::from(name_id) + nums[4]) as u32;
                                if name_id >= names.len() as u32 {
                                    bail!("invalid name reference: {name_id}");
                                }
                                name = name_id;
                            }
                        }

                        tokens.push(RawToken {
                            dst_line: dst_line as u32,
                            dst_col,
                            src_line,
                            src_col,
                            src_id: src,
                            name_id: name,
                            is_range: false,
                        });
                    }
                }

                let mut map = SourceMap::new(

View on GitHub (pinned to 5176682b65)

Solutions

1. Regenerate the source map from the original tool so `names` and `mappings` stay consistent
2. If name mappings are not needed, strip the 5th field from segments as well when stripping `names` (or set names to match indices)
3. Validate with a standard source-map library first to pinpoint the inconsistent segment
4. Pass the map as a JSON string or omit it if not required by your pipeline

Example fix

// before: names array dropped but mappings still reference it
map.names = vec![];

// after: keep names, or regenerate the map wholesale
// (preferred) let fresh = producer.generate_source_map();

// Cheap consistency gate: if you strip `names`, ensure no 5-field segments remain
function hasNameRefs(mappings) { /* decode VLQ; true if any segment has 5 fields */ }
if (map.names.length === 0 && hasNameRefs(map.mappings)) throw new Error('mappings reference missing names');

try { await transform(src, { inputSourceMap: map }) } catch (e) { if (/invalid name reference/.test(e.message)) { return transform(src, {}); } throw e; }

When it happens

Trigger: Supplying a parsed input source map whose `names` array was stripped (e.g. minified down to save bytes) while mappings still contain 5-field segments with name deltas; or splicing mappings from another file.

Common situations: Source map post-processors that drop or truncate the `names` array for size; merging/concatenating source maps without remapping name indices; producer tools emitting inconsistent maps after renaming passes; cached stale maps after a build change.

Related errors

• invalid source reference: {src_id}
• invalid vlq segment size; expected 4 or 5, got {}
• InvalidData
• invalid utf8
• Failed to convert RawValue to Data

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/a342a4ee905069ab. Report an issue: GitHub.