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Diffstat (limited to 'compiler/sourcemap.nim')
| -rw-r--r-- | compiler/sourcemap.nim | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/compiler/sourcemap.nim b/compiler/sourcemap.nim new file mode 100644 index 000000000..1395168cd --- /dev/null +++ b/compiler/sourcemap.nim @@ -0,0 +1,206 @@ +import std/[strutils, strscans, parseutils, assertions] + +type + Segment = object + ## Segment refers to a block of something in the JS output. + ## This could be a token or an entire line + original: int # Column in the Nim source + generated: int # Column in the generated JS + name: int # Index into names list (-1 for no name) + + Mapping = object + ## Mapping refers to a line in the JS output. + ## It is made up of segments which refer to the tokens in the line + case inSource: bool # Whether the line in JS has Nim equivalent + of true: + file: int # Index into files list + line: int # 0 indexed line of code in the Nim source + segments: seq[Segment] + else: discard + + SourceInfo = object + mappings: seq[Mapping] + names, files: seq[string] + + SourceMap* = object + version*: int + sources*: seq[string] + names*: seq[string] + mappings*: string + file*: string + +func addSegment(info: var SourceInfo, original, generated: int, name: string = "") {.raises: [].} = + ## Adds a new segment into the current line + assert info.mappings.len > 0, "No lines have been added yet" + var segment = Segment(original: original, generated: generated, name: -1) + if name != "": + # Make name be index into names list + segment.name = info.names.find(name) + if segment.name == -1: + segment.name = info.names.len + info.names &= name + + assert info.mappings[^1].inSource, "Current line isn't in Nim source" + info.mappings[^1].segments &= segment + +func newLine(info: var SourceInfo) {.raises: [].} = + ## Add new mapping which doesn't appear in the Nim source + info.mappings &= Mapping(inSource: false) + +func newLine(info: var SourceInfo, file: string, line: int) {.raises: [].} = + ## Starts a new line in the mappings. Call addSegment after this to add + ## segments into the line + var mapping = Mapping(inSource: true, line: line) + # Set file to file position. Add in if needed + mapping.file = info.files.find(file) + if mapping.file == -1: + mapping.file = info.files.len + info.files &= file + info.mappings &= mapping + + +# base64_VLQ +func encode*(values: seq[int]): string {.raises: [].} = + ## Encodes a series of integers into a VLQ base64 encoded string + # References: + # - https://www.lucidchart.com/techblog/2019/08/22/decode-encoding-base64-vlqs-source-maps/ + # - https://github.com/rails/sprockets/blob/main/guides/source_maps.md#source-map-file + const + alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" + shift = 5 + continueBit = 1 shl 5 + mask = continueBit - 1 + result = "" + for val in values: + # Sign is stored in first bit + var newVal = abs(val) shl 1 + if val < 0: + newVal = newVal or 1 + # Now comes the variable length part + # This is how we are able to store large numbers + while true: + # We only encode 5 bits. + var masked = newVal and mask + newVal = newVal shr shift + # If there is still something left + # then signify with the continue bit that the + # decoder should keep decoding + if newVal > 0: + masked = masked or continueBit + result &= alphabet[masked] + # If the value is zero then we have nothing left to encode + if newVal == 0: + break + +iterator tokenize*(line: string): (int, string) = + ## Goes through a line and splits it into Nim identifiers and + ## normal JS code. This allows us to map mangled names back to Nim names. + ## Yields (column, name). Doesn't yield anything but identifiers. + ## See mangleName in compiler/jsgen.nim for how name mangling is done + var + col = 0 + token = "" + while col < line.len: + var + token: string = "" + name: string = "" + # First we find the next identifier + col += line.skipWhitespace(col) + col += line.skipUntil(IdentStartChars, col) + let identStart = col + col += line.parseIdent(token, col) + # Idents will either be originalName_randomInt or HEXhexCode_randomInt + if token.startsWith("HEX"): + var hex: int = 0 + # 3 = "HEX".len and we only want to parse the two integers after it + discard token[3 ..< 5].parseHex(hex) + name = $chr(hex) + elif not token.endsWith("_Idx"): # Ignore address indexes + # It might be in the form originalName_randomInt + let lastUnderscore = token.rfind('_') + if lastUnderscore != -1: + name = token[0..<lastUnderscore] + if name != "": + yield (identStart, name) + +func parse*(source: string): SourceInfo = + ## Parses the JS output for embedded line info + ## So it can convert those into a series of mappings + result = default(SourceInfo) + var + skipFirstLine = true + currColumn = 0 + currLine = 0 + currFile = "" + # Add each line as a node into the output + for line in source.splitLines(): + var + lineNumber: int = 0 + linePath: string = "" + column: int = 0 + if line.strip().scanf("/* line $i:$i \"$+\" */", lineNumber, column, linePath): + # When we reach the first line mappinsegmentg then we can assume + # we can map the rest of the JS lines to Nim lines + currColumn = column # Column is already zero indexed + currLine = lineNumber - 1 + currFile = linePath + # Lines are zero indexed + result.newLine(currFile, currLine) + # Skip whitespace to find the starting column + result.addSegment(currColumn, line.skipWhitespace()) + elif currFile != "": + result.newLine(currFile, currLine) + # There mightn't be any tokens so add a starting segment + result.addSegment(currColumn, line.skipWhitespace()) + for jsColumn, token in line.tokenize: + result.addSegment(currColumn, jsColumn, token) + else: + result.newLine() + +func toSourceMap*(info: SourceInfo, file: string): SourceMap {.raises: [].} = + ## Convert from high level SourceInfo into the required SourceMap object + # Add basic info + result = SourceMap(version: 3, file: file, sources: info.files, names: info.names) + # Convert nodes into mappings. + # Mappings are split into blocks where each block referes to a line in the outputted JS. + # Blocks can be separated into statements which refere to tokens on the line. + # Since the mappings depend on previous values we need to + # keep track of previous file, name, etc + var + prevFile = 0 + prevLine = 0 + prevName = 0 + prevNimCol = 0 + + for mapping in info.mappings: + # We know need to encode segments with the following fields + # All these fields are relative to their previous values + # - 0: Column in generated code + # - 1: Index of Nim file in source list + # - 2: Line in Nim source + # - 3: Column in Nim source + # - 4: Index in names list + if mapping.inSource: + # JS Column is special in that it is reset after every line + var prevJSCol = 0 + for segment in mapping.segments: + var values = @[segment.generated - prevJSCol, mapping.file - prevFile, mapping.line - prevLine, segment.original - prevNimCol] + # Add name field if needed + if segment.name != -1: + values &= segment.name - prevName + prevName = segment.name + prevJSCol = segment.generated + prevNimCol = segment.original + prevFile = mapping.file + prevLine = mapping.line + result.mappings &= encode(values) & "," + # Remove trailing , + if mapping.segments.len > 0: + result.mappings.setLen(result.mappings.len - 1) + + result.mappings &= ";" + +proc genSourceMap*(source: string, outFile: string): SourceMap = + let node = parse(source) + result = node.toSourceMap(outFile) + |