Function createExternalSource

src/data/helper/transform.ts:162–260

(internalSource: Source, externalTransform: ExternalDataTransform)

function createExternalSource(internalSource: Source, externalTransform: ExternalDataTransform): ExternalSource {
    const extSource = new ExternalSource();

    const data = internalSource.data;
    const sourceFormat = extSource.sourceFormat = internalSource.sourceFormat;
    const sourceHeaderCount = internalSource.startIndex;

    let errMsg = '';
    if (internalSource.seriesLayoutBy !== SERIES_LAYOUT_BY_COLUMN) {
        // For the logic simplicity in transformer, only 'culumn' is
        // supported in data transform. Otherwise, the `dimensionsDefine`
        // might be detected by 'row', which probably confuses users.
        if (__DEV__) {
            errMsg = '`seriesLayoutBy` of upstream dataset can only be "column" in data transform.';
        }
        throwError(errMsg);
    }

    // [MEMO]
    // Create a new dimensions structure for exposing.
    // Do not expose all dimension info to users directly.
    // Because the dimension is probably auto detected from data and not might reliable.
    // Should not lead the transformers to think that is reliable and return it.
    // See [DIMENSION_INHERIT_RULE] in `sourceManager.ts`.
    const dimensions = [] as ExternalDimensionDefinition[];
    const dimsByName = {} as Dictionary<ExternalDimensionDefinition>;

    const dimsDef = internalSource.dimensionsDefine;
    if (dimsDef) {
        each(dimsDef, function (dimDef, idx) {
            const name = dimDef.name;
            const dimDefExt = {
                index: idx,
                name: name,
                displayName: dimDef.displayName
            };
            dimensions.push(dimDefExt);
            // Users probably do not specify dimension name. For simplicity, data transform
            // does not generate dimension name.
            if (name != null) {
                // Dimension name should not be duplicated.
                // For simplicity, data transform forbids name duplication, do not generate
                // new name like module `completeDimensions.ts` did, but just tell users.
                let errMsg = '';
                if (hasOwn(dimsByName, name)) {
                    if (__DEV__) {
                        errMsg = 'dimension name "' + name + '" duplicated.';
                    }
                    throwError(errMsg);
                }
                dimsByName[name] = dimDefExt;
            }
        });
    }
    // If dimension definitions are not defined and can not be detected.
    // e.g., pure data `[[11, 22], ...]`.
    else {
        for (let i = 0; i < internalSource.dimensionsDetectedCount || 0; i++) {