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Move
Dockerfile parsing to a dedicated package
Also, add a bunch of test cases / code coverage
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,124 @@ | ||
| package dockerfile | ||
|
|
||
| import ( | ||
| "bufio" | ||
| "io" | ||
| "strconv" | ||
| "strings" | ||
| ) | ||
|
|
||
| type Metadata struct { | ||
| StageFroms []string // every image "FROM" instruction value (or the parent stage's FROM value in the case of a named stage) | ||
| StageNames []string // the name of any named stage (in order) | ||
| StageNameFroms map[string]string // map of stage names to FROM values (or the parent stage's FROM value in the case of a named stage), useful for resolving stage names to FROM values | ||
|
|
||
| Froms []string // every "FROM" or "COPY --from=xxx" value (minus named and/or numbered stages in the case of "--from=") | ||
| } | ||
|
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| func Parse(dockerfile string) (*Metadata, error) { | ||
| return ParseReader(strings.NewReader(dockerfile)) | ||
| } | ||
|
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| func ParseReader(dockerfile io.Reader) (*Metadata, error) { | ||
| meta := &Metadata{ | ||
| // panic: assignment to entry in nil map | ||
| StageNameFroms: map[string]string{}, | ||
| // (nil slices work fine) | ||
| } | ||
|
|
||
| scanner := bufio.NewScanner(dockerfile) | ||
| for scanner.Scan() { | ||
| line := strings.TrimSpace(scanner.Text()) | ||
|
|
||
| if line == "" { | ||
| // ignore blank lines | ||
| continue | ||
| } | ||
|
|
||
| if line[0] == '#' { | ||
| // TODO handle "escape" parser directive | ||
| // TODO handle "syntax" parser directive -- explode appropriately (since custom syntax invalidates our Dockerfile parsing) | ||
| // ignore comments | ||
| continue | ||
| } | ||
|
|
||
| // handle line continuations | ||
| // (TODO see note above regarding "escape" parser directive) | ||
| for line[len(line)-1] == '\\' && scanner.Scan() { | ||
| nextLine := strings.TrimSpace(scanner.Text()) | ||
| if nextLine == "" || nextLine[0] == '#' { | ||
| // ignore blank lines and comments | ||
| continue | ||
| } | ||
| line = line[0:len(line)-1] + nextLine | ||
| } | ||
|
|
||
| fields := strings.Fields(line) | ||
| if len(fields) < 1 { | ||
| // must be a much more complex empty line?? | ||
| continue | ||
| } | ||
| instruction := strings.ToUpper(fields[0]) | ||
|
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||
| // TODO balk at ARG / $ in from values | ||
|
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| switch instruction { | ||
| case "FROM": | ||
| from := fields[1] | ||
|
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| if stageFrom, ok := meta.StageNameFroms[from]; ok { | ||
| // if this is a valid stage name, we should resolve it back to the original FROM value of that previous stage (we don't care about inter-stage dependencies for the purposes of either tag dependency calculation or tag building -- just how many there are and what external things they require) | ||
| from = stageFrom | ||
| } | ||
|
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||
| // make sure to add ":latest" if it's implied | ||
| from = latestizeRepoTag(from) | ||
|
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| meta.StageFroms = append(meta.StageFroms, from) | ||
| meta.Froms = append(meta.Froms, from) | ||
|
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| if len(fields) == 4 && strings.ToUpper(fields[2]) == "AS" { | ||
| stageName := fields[3] | ||
| meta.StageNames = append(meta.StageNames, stageName) | ||
| meta.StageNameFroms[stageName] = from | ||
| } | ||
|
|
||
| case "COPY": | ||
| for _, arg := range fields[1:] { | ||
| if !strings.HasPrefix(arg, "--") { | ||
| // doesn't appear to be a "flag"; time to bail! | ||
| break | ||
| } | ||
| if !strings.HasPrefix(arg, "--from=") { | ||
| // ignore any flags we're not interested in | ||
| continue | ||
| } | ||
| from := arg[len("--from="):] | ||
|
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| if stageFrom, ok := meta.StageNameFroms[from]; ok { | ||
| // see note above regarding stage names in FROM | ||
| from = stageFrom | ||
| } else if stageNumber, err := strconv.Atoi(from); err == nil && stageNumber < len(meta.StageFroms) { | ||
| // must be a stage number, we should resolve it too | ||
| from = meta.StageFroms[stageNumber] | ||
| } | ||
|
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| // make sure to add ":latest" if it's implied | ||
| from = latestizeRepoTag(from) | ||
|
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| meta.Froms = append(meta.Froms, from) | ||
| } | ||
| } | ||
| } | ||
| if err := scanner.Err(); err != nil { | ||
| return nil, err | ||
| } | ||
| return meta, nil | ||
| } | ||
|
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||
| func latestizeRepoTag(repoTag string) string { | ||
| if repoTag != "scratch" && strings.IndexRune(repoTag, ':') < 0 { | ||
| return repoTag + ":latest" | ||
| } | ||
| return repoTag | ||
| } |
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