Improve compilation errors output

[ldez]

Fixes #1002
Related to #1820 and #886

I think this also fixes partially #1792 (#1792 (comment))

This PR will improve in the report when the analyzed code contains compilation errors.

It's a bit complex to explain but I will try to explain it.

typecheck is like the front-end of a Go compiler, parses and type-checks Go code.
This linter is able to manage compilation error, that's his role.
So this linter must be the first linter.

To put typecheck as the first linter, I improved the sort of the linters inside enabled_set.go and I changed the load mode to goanalysis.LoadModeWholeProgram (because the linters with goanalysis.LoadModeWholeProgram are not put inside the metalinter and they are executed before the metalinter)

This change will not improve the output when only one linter is launched, it's another topic.
But I think that the output will be better in 90% of the use-cases: when several linters (including typecheck) are run

Before my PR

$ golangci-lint run
WARN [runner] Can't run linter goanalysis_metalinter: bodyclose: failed prerequisites: [buildssa@github.com/golangci/golangci-lint/pkg/lint: analysis skipped: errors in package: [/home/ldez/sources/go/src/github.com/golangci/golangci-lint/pkg/lint/runner.go:18:2: could not import github.com/golangci/golangci-lint/pkg/lint/lintersdb (/home/ldez/sources/go/src/github.com/golangci/golangci-lint/pkg/lint/lintersdb/manager.go:13:2: could not import github.com/golangci/golangci-lint/pkg/golinters (/home/ldez/sources/go/src/github.com/golangci/golangci-lint/pkg/golinters/deadcode.go:21:9: undeclared name: linterName)) /home/ldez/sources/go/src/github.com/golangci/golangci-lint/pkg/lint/runner.go:22:2: could not import github.com/golangci/golangci-lint/pkg/result/processors (/home/ldez/sources/go/src/github.com/golangci/golangci-lint/pkg/result/processors/nolint.go:11:2: could not import github.com/golangci/golangci-lint/pkg/golinters (/home/ldez/sources/go/src/github.com/golangci/golangci-lint/pkg/golinters/deadcode.go:21:9: undeclared name: linterName))]] 
WARN [runner] Can't run linter unused: buildir: failed to load package golinters: could not load export data: no export data for "github.com/golangci/golangci-lint/pkg/golinters" 
ERRO Running error: buildir: failed to load package golinters: could not load export data: no export data for "github.com/golangci/golangci-lint/pkg/golinters"

With my PR

$ ./golangci-lint run
pkg/lint/runner.go:18:2: could not import github.com/golangci/golangci-lint/pkg/lint/lintersdb (pkg/lint/lintersdb/manager.go:13:2: could not import github.com/golangci/golangci-lint/pkg/golinters (pkg/golinters/deadcode.go:21:9: undeclared name: linterName)) (typecheck)
        "github.com/golangci/golangci-lint/pkg/lint/lintersdb"
        ^
pkg/lint/runner.go:22:2: could not import github.com/golangci/golangci-lint/pkg/result/processors (pkg/result/processors/nolint.go:11:2: could not import github.com/golangci/golangci-lint/pkg/golinters (pkg/golinters/deadcode.go:21:9: undeclared name: linterName)) (typecheck)
        "github.com/golangci/golangci-lint/pkg/result/processors"
        ^
pkg/commands/executor.go:26:2: could not import github.com/golangci/golangci-lint/pkg/lint (pkg/lint/runner.go:18:2: could not import github.com/golangci/golangci-lint/pkg/lint/lintersdb (pkg/lint/lintersdb/manager.go:13:2: could not import github.com/golangci/golangci-lint/pkg/golinters (pkg/golinters/deadcode.go:21:9: undeclared name: linterName))) (typecheck)
        "github.com/golangci/golangci-lint/pkg/lint"
        ^
pkg/commands/executor.go:27:2: could not import github.com/golangci/golangci-lint/pkg/lint/lintersdb (pkg/lint/lintersdb/manager.go:13:2: could not import github.com/golangci/golangci-lint/pkg/golinters (pkg/golinters/deadcode.go:21:9: undeclared name: linterName)) (typecheck)
        "github.com/golangci/golangci-lint/pkg/lint/lintersdb"
        ^
pkg/commands/run.go:26:2: could not import github.com/golangci/golangci-lint/pkg/result/processors (pkg/result/processors/nolint.go:11:2: could not import github.com/golangci/golangci-lint/pkg/golinters (pkg/golinters/deadcode.go:21:9: undeclared name: linterName)) (typecheck)
        "github.com/golangci/golangci-lint/pkg/result/processors"
        ^
cmd/golangci-lint/main.go:7:2: could not import github.com/golangci/golangci-lint/pkg/commands (pkg/commands/executor.go:26:2: could not import github.com/golangci/golangci-lint/pkg/lint (pkg/lint/runner.go:18:2: could not import github.com/golangci/golangci-lint/pkg/lint/lintersdb (pkg/lint/lintersdb/manager.go:13:2: could not import github.com/golangci/golangci-lint/pkg/golinters (pkg/golinters/deadcode.go:21:9: undeclared name: linterName)))) (typecheck)
        "github.com/golangci/golangci-lint/pkg/commands"
        ^
scripts/expand_website_templates/main.go:21:2: could not import github.com/golangci/golangci-lint/pkg/lint/lintersdb (pkg/lint/lintersdb/manager.go:13:2: could not import github.com/golangci/golangci-lint/pkg/golinters (pkg/golinters/deadcode.go:21:9: undeclared name: linterName)) (typecheck)
        "github.com/golangci/golangci-lint/pkg/lint/lintersdb"
        ^
pkg/golinters/deadcode.go:21:9: undeclared name: `linterName` (typecheck)
                Name: linterName,
                      ^
pkg/lint/lintersdb/manager.go:13:2: could not import github.com/golangci/golangci-lint/pkg/golinters (pkg/golinters/deadcode.go:21:9: undeclared name: linterName) (typecheck)
        "github.com/golangci/golangci-lint/pkg/golinters"
        ^
pkg/lint/lintersdb/manager.go:501:2: isLocalRun declared but not used (typecheck)
        isLocalRun := os.Getenv("GOLANGCI_COM_RUN") == ""
        ^
pkg/result/processors/nolint.go:11:2: could not import github.com/golangci/golangci-lint/pkg/golinters (pkg/golinters/deadcode.go:21:9: undeclared name: linterName) (typecheck)
        "github.com/golangci/golangci-lint/pkg/golinters"
        ^

[bombsimon]

Wow, awesome job! Does typecheck list all compilation errors by being run first? If so, this pretty much solves all issues asking for this!

[ldez]

FYI typecheck is not a real linter it's just a way to parse some error.
The code in pkg/golinters/typecheck.go is just a kind of placeholder.

golangci-lint/pkg/golinters/typecheck.go

Lines 14 to 16 in 8db518c

	Run: func(pass *analysis.Pass) (interface{}, error) {
	return nil, nil
	},

The real code is here:

golangci-lint/pkg/golinters/goanalysis/linter.go

Lines 180 to 216 in 8db518c

	func parseError(srcErr packages.Error) (*result.Issue, error) {
	pos, err := libpackages.ParseErrorPosition(srcErr.Pos)
	if err != nil {
	return nil, err
	}
	return &result.Issue{
	Pos: *pos,
	Text: srcErr.Msg,
	FromLinter: "typecheck",
	}, nil
	}
	func buildIssuesFromErrorsForTypecheckMode(errs []error, lintCtx *linter.Context) ([]result.Issue, error) {
	var issues []result.Issue
	uniqReportedIssues := map[string]bool{}
	for _, err := range errs {
	itErr, ok := errors.Cause(err).(*IllTypedError)
	if !ok {
	return nil, err
	}
	for _, err := range libpackages.ExtractErrors(itErr.Pkg) {
	i, perr := parseError(err)
	if perr != nil { // failed to parse
	if uniqReportedIssues[err.Msg] {
	continue
	}
	uniqReportedIssues[err.Msg] = true
	lintCtx.Log.Errorf("typechecking error: %s", err.Msg)
	} else {
	i.Pkg = itErr.Pkg // to save to cache later
	issues = append(issues, *i)
	}
	}
	}
	return issues, nil
	}

Currently, I try to handle a side effect of using LoadModeWholeProgram on typecheck.
So I'm trying to change the core system to handle errors, if I succeed all the issues related to the compilation errors message will be fixed.

[ldez]

I think that I found the "ultimate" fix 🎉

But for that, I will reorganize the code without any changes, and after I will fix the core problem.
This will produce a lot of changes because I will just move the code.

My plan:

• drop all my commits
• split the pkg/golinters/goanalysis/runner.go file into multiple files (because it's a pain to debug a 1500 lines file with recursive calls, with multiple struct and multiple embedded and anonymous functions)
• apply the "ultimate fix"
• fix the sorting of the linters to fix the randomness of the result of the analysis

Maybe I will create another PR 🤔

[ldez]

Superseded by #1861