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98 lines
2.9 KiB
Go
98 lines
2.9 KiB
Go
package cli
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// ================================================================
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// Decide whether to insert a flatten or unflatten verb at the end of the
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// chain. See also repl/verbs.go which handles the same issue in the REPL.
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//
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// ----------------------------------------------------------------
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// PROBLEM TO BE SOLVED:
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//
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// JSON has nested structures and CSV et al. do not. For example:
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// {
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// "req" : {
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// "method": "GET",
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// "path": "api/check",
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// }
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// }
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//
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// For CSV we flatten this down to
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//
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// {
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// "req.method": "GET",
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// "req.path": "api/check"
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// }
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//
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// ----------------------------------------------------------------
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// APPROACH:
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//
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// Use the Principle of Least Surprise (POLS).
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//
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// * If input is JSON and output is JSON:
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// o Records can be nested from record-read
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// o They remain that way through the Miller record-processing stream
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// o They are nested on record-write
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// o No action needs to be taken
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//
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// * If input is JSON and output is non-JSON:
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// o Records can be nested from record-read
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// o They remain that way through the Miller record-processing stream
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// o On record-write, nested structures will be converted to string (carriage
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// returns and all) using json_stringify. People *might* want this but
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// (using POLS) we will (by default) AUTO-FLATTEN for them. There is a
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// --no-auto-unflatten CLI flag for those who want it.
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//
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// * If input is non-JSON and output is non-JSON:
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// o If there is a "req.method" field, people should be able to do
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// 'mlr sort -f req.method' with no surprises. (Again, POLS.) Therefore
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// no auto-unflatten on input. People can insert an unflatten verb
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// into their verb chain if they really want unflatten for non-JSON
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// files.
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// o The DSL can make nested data, so AUTO-FLATTEN at output.
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//
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// * If input is non-JSON and output is JSON:
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// o Default is to auto-unflatten at output.
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// o There is a --no-auto-unflatten for those who want it.
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//
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// * Overriding these: if the last verb the user has explicitly provided is
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// flatten, don't undo that by putting an unflatten right after.
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//
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// ================================================================
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func DecideFinalFlatten(writerOptions *TWriterOptions) bool {
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ofmt := writerOptions.OutputFileFormat
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if writerOptions.AutoFlatten {
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if ofmt != "json" {
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return true
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}
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}
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return false
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}
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func DecideFinalUnflatten(
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options *TOptions,
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verbSequences [][]string,
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) bool {
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numVerbs := len(verbSequences)
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if numVerbs > 0 {
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lastVerbSequence := verbSequences[numVerbs-1]
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if len(lastVerbSequence) > 0 {
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lastVerbName := lastVerbSequence[0]
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if lastVerbName == "flatten" {
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return false
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}
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}
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}
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ifmt := options.ReaderOptions.InputFileFormat
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ofmt := options.WriterOptions.OutputFileFormat
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if options.WriterOptions.AutoUnflatten {
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if ifmt != "json" {
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if ofmt == "json" {
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return true
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}
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}
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}
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return false
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}
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