completion: Improve existing argument completions, add many more

Do not offer filenames to arguments not taking one, complete arguments
of options taking resource kinds, directory names, --logLevel, release
--step, config and new --format.

As an internal refactoring, use higher level functions to set flag
completions.  SetAnnotation works, but is more verbose than
alternatives, and uses bash specific wording.

While at it, move setting completions next to flag definitions
consistently.

Remove superfluous --destination completer setting, which is already
set elsewhere.

12 files changed, 93 insertions, 19 deletions

diff --git a/commands/commandeer.go b/commands/commandeer.go
index a0e4e3836..f18c3f813 100644
--- a/commands/commandeer.go
+++ b/commands/commandeer.go
@@ -48,6 +48,7 @@ import (
 	"github.com/gohugoio/hugo/helpers"
 	"github.com/gohugoio/hugo/hugofs"
 	"github.com/gohugoio/hugo/hugolib"
+	"github.com/gohugoio/hugo/resources/kinds"
 	"github.com/spf13/afero"
 	"github.com/spf13/cobra"
 )
@@ -482,47 +483,47 @@ Complete documentation is available at https://gohugo.io/.`
 
 	// Configure persistent flags
 	cmd.PersistentFlags().StringVarP(&r.source, "source", "s", "", "filesystem path to read files relative from")
-	cmd.PersistentFlags().SetAnnotation("source", cobra.BashCompSubdirsInDir, []string{})
+	_ = cmd.MarkFlagDirname("source")
 	cmd.PersistentFlags().StringP("destination", "d", "", "filesystem path to write files to")
-	cmd.PersistentFlags().SetAnnotation("destination", cobra.BashCompSubdirsInDir, []string{})
+	_ = cmd.MarkFlagDirname("destination")
 
 	cmd.PersistentFlags().StringVarP(&r.environment, "environment", "e", "", "build environment")
+	_ = cmd.RegisterFlagCompletionFunc("environment", cobra.NoFileCompletions)
 	cmd.PersistentFlags().StringP("themesDir", "", "", "filesystem path to themes directory")
+	_ = cmd.MarkFlagDirname("themesDir")
 	cmd.PersistentFlags().StringP("ignoreVendorPaths", "", "", "ignores any _vendor for module paths matching the given Glob pattern")
+	_ = cmd.RegisterFlagCompletionFunc("ignoreVendorPaths", cobra.NoFileCompletions)
 	cmd.PersistentFlags().String("clock", "", "set the clock used by Hugo, e.g. --clock 2021-11-06T22:30:00.00+09:00")
+	_ = cmd.RegisterFlagCompletionFunc("clock", cobra.NoFileCompletions)
 
 	cmd.PersistentFlags().StringVar(&r.cfgFile, "config", "", "config file (default is hugo.yaml|json|toml)")
+	_ = cmd.MarkFlagFilename("config", config.ValidConfigFileExtensions...)
 	cmd.PersistentFlags().StringVar(&r.cfgDir, "configDir", "config", "config dir")
+	_ = cmd.MarkFlagDirname("configDir")
 	cmd.PersistentFlags().BoolVar(&r.quiet, "quiet", false, "build in quiet mode")
 	cmd.PersistentFlags().BoolVar(&r.renderToMemory, "renderToMemory", false, "render to memory (mostly useful when running the server)")
 
-	// Set bash-completion
-	_ = cmd.PersistentFlags().SetAnnotation("config", cobra.BashCompFilenameExt, config.ValidConfigFileExtensions)
-
 	cmd.PersistentFlags().BoolVarP(&r.verbose, "verbose", "v", false, "verbose output")
 	cmd.PersistentFlags().BoolVarP(&r.debug, "debug", "", false, "debug output")
 	cmd.PersistentFlags().StringVar(&r.logLevel, "logLevel", "", "log level (debug|info|warn|error)")
+	_ = cmd.RegisterFlagCompletionFunc("logLevel", cobra.FixedCompletions([]string{"debug", "info", "warn", "error"}, cobra.ShellCompDirectiveNoFileComp))
 	cmd.Flags().BoolVarP(&r.buildWatch, "watch", "w", false, "watch filesystem for changes and recreate as needed")
 
 	// Configure local flags
 	applyLocalFlagsBuild(cmd, r)
 
-	// Set bash-completion.
-	// Each flag must first be defined before using the SetAnnotation() call.
-	_ = cmd.Flags().SetAnnotation("source", cobra.BashCompSubdirsInDir, []string{})
-
 	return nil
 }
 
 // A sub set of the complete build flags. These flags are used by new and mod.
 func applyLocalFlagsBuildConfig(cmd *cobra.Command, r *rootCommand) {
 	cmd.Flags().StringSliceP("theme", "t", []string{}, "themes to use (located in /themes/THEMENAME/)")
+	_ = cmd.MarkFlagDirname("theme")
 	cmd.Flags().StringVarP(&r.baseURL, "baseURL", "b", "", "hostname (and path) to the root, e.g. https://spf13.com/")
 	cmd.Flags().StringP("cacheDir", "", "", "filesystem path to cache directory")
-	_ = cmd.Flags().SetAnnotation("cacheDir", cobra.BashCompSubdirsInDir, []string{})
+	_ = cmd.MarkFlagDirname("cacheDir")
 	cmd.Flags().StringP("contentDir", "c", "", "filesystem path to content directory")
 	cmd.Flags().StringSliceP("renderSegments", "", []string{}, "named segments to render (configured in the segments config)")
-	_ = cmd.Flags().SetAnnotation("theme", cobra.BashCompSubdirsInDir, []string{"themes"})
 }
 
 // Flags needed to do a build (used by hugo and hugo server commands)
@@ -535,8 +536,10 @@ func applyLocalFlagsBuild(cmd *cobra.Command, r *rootCommand) {
 	cmd.Flags().BoolP("ignoreCache", "", false, "ignores the cache directory")
 	cmd.Flags().Bool("enableGitInfo", false, "add Git revision, date, author, and CODEOWNERS info to the pages")
 	cmd.Flags().StringP("layoutDir", "l", "", "filesystem path to layout directory")
+	_ = cmd.MarkFlagDirname("layoutDir")
 	cmd.Flags().BoolVar(&r.gc, "gc", false, "enable to run some cleanup tasks (remove unused cache files) after the build")
 	cmd.Flags().StringVar(&r.poll, "poll", "", "set this to a poll interval, e.g --poll 700ms, to use a poll based approach to watch for file system changes")
+	_ = cmd.RegisterFlagCompletionFunc("poll", cobra.NoFileCompletions)
 	cmd.Flags().Bool("panicOnWarning", false, "panic on first WARNING log")
 	cmd.Flags().Bool("templateMetrics", false, "display metrics about template executions")
 	cmd.Flags().Bool("templateMetricsHints", false, "calculate some improvement hints when combined with --templateMetrics")
@@ -559,8 +562,8 @@ func applyLocalFlagsBuild(cmd *cobra.Command, r *rootCommand) {
 	cmd.Flags().MarkHidden("profile-mutex")
 
 	cmd.Flags().StringSlice("disableKinds", []string{}, "disable different kind of pages (home, RSS etc.)")
+	_ = cmd.RegisterFlagCompletionFunc("disableKinds", cobra.FixedCompletions(kinds.AllKinds, cobra.ShellCompDirectiveNoFileComp))
 	cmd.Flags().Bool("minify", false, "minify any supported output format (HTML, XML etc.)")
-	_ = cmd.Flags().SetAnnotation("destination", cobra.BashCompSubdirsInDir, []string{})
 }
 
 func (r *rootCommand) timeTrack(start time.Time, name string) {
diff --git a/commands/config.go b/commands/config.go
index dfe54cba2..adf6bbe2b 100644
--- a/commands/config.go
+++ b/commands/config.go
@@ -28,6 +28,7 @@ import (
 	"github.com/gohugoio/hugo/modules"
 	"github.com/gohugoio/hugo/parser"
 	"github.com/gohugoio/hugo/parser/metadecoders"
+	"github.com/spf13/cobra"
 )
 
 // newConfigCommand creates a new config command and its subcommands.
@@ -112,7 +113,9 @@ func (c *configCommand) Init(cd *simplecobra.Commandeer) error {
 	cmd.Short = "Print the site configuration"
 	cmd.Long = `Print the site configuration, both default and custom settings.`
 	cmd.Flags().StringVar(&c.format, "format", "toml", "preferred file format (toml, yaml or json)")
+	_ = cmd.RegisterFlagCompletionFunc("format", cobra.FixedCompletions([]string{"toml", "yaml", "json"}, cobra.ShellCompDirectiveNoFileComp))
 	cmd.Flags().StringVar(&c.lang, "lang", "", "the language to display config for. Defaults to the first language defined.")
+	_ = cmd.RegisterFlagCompletionFunc("lang", cobra.NoFileCompletions)
 	applyLocalFlagsBuildConfig(cmd, c.r)
 
 	return nil
@@ -223,6 +226,7 @@ func (c *configMountsCommand) Init(cd *simplecobra.Commandeer) error {
 	c.r = cd.Root.Command.(*rootCommand)
 	cmd := cd.CobraCommand
 	cmd.Short = "Print the configured file mounts"
+	cmd.ValidArgsFunction = cobra.NoFileCompletions
 	applyLocalFlagsBuildConfig(cmd, c.r)
 	return nil
 }
diff --git a/commands/convert.go b/commands/convert.go
index c81ec792a..4e1ceb7d1 100644
--- a/commands/convert.go
+++ b/commands/convert.go
@@ -46,6 +46,7 @@ to use JSON for the front matter.`,
 					return c.convertContents(metadecoders.JSON)
 				},
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 				},
 			},
 			&simpleCommand{
@@ -57,6 +58,7 @@ to use TOML for the front matter.`,
 					return c.convertContents(metadecoders.TOML)
 				},
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 				},
 			},
 			&simpleCommand{
@@ -68,6 +70,7 @@ to use YAML for the front matter.`,
 					return c.convertContents(metadecoders.YAML)
 				},
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 				},
 			},
 		},
@@ -108,6 +111,7 @@ func (c *convertCommand) Init(cd *simplecobra.Commandeer) error {
 See convert's subcommands toJSON, toTOML and toYAML for more information.`
 
 	cmd.PersistentFlags().StringVarP(&c.outputDir, "output", "o", "", "filesystem path to write files to")
+	_ = cmd.MarkFlagDirname("output")
 	cmd.PersistentFlags().BoolVar(&c.unsafe, "unsafe", false, "enable less safe operations, please backup first")
 
 	cmd.RunE = nil
diff --git a/commands/deploy.go b/commands/deploy.go
index f5354f74d..873da14a4 100644
--- a/commands/deploy.go
+++ b/commands/deploy.go
@@ -60,13 +60,17 @@ documentation.
 			return deployer.Deploy(ctx)
 		},
 		withc: func(cmd *cobra.Command, r *rootCommand) {
+			cmd.ValidArgsFunction = cobra.NoFileCompletions
 			cmd.Flags().String("target", "", "target deployment from deployments section in config file; defaults to the first one")
+			_ = cmd.RegisterFlagCompletionFunc("target", cobra.NoFileCompletions)
 			cmd.Flags().Bool("confirm", false, "ask for confirmation before making changes to the target")
 			cmd.Flags().Bool("dryRun", false, "dry run")
 			cmd.Flags().Bool("force", false, "force upload of all files")
 			cmd.Flags().Bool("invalidateCDN", deployconfig.DefaultConfig.InvalidateCDN, "invalidate the CDN cache listed in the deployment target")
 			cmd.Flags().Int("maxDeletes", deployconfig.DefaultConfig.MaxDeletes, "maximum # of files to delete, or -1 to disable")
+			_ = cmd.RegisterFlagCompletionFunc("maxDeletes", cobra.NoFileCompletions)
 			cmd.Flags().Int("workers", deployconfig.DefaultConfig.Workers, "number of workers to transfer files. defaults to 10")
+			_ = cmd.RegisterFlagCompletionFunc("workers", cobra.NoFileCompletions)
 		},
 	}
 }
diff --git a/commands/env.go b/commands/env.go
index 8e4f03c55..843fc49d1 100644
--- a/commands/env.go
+++ b/commands/env.go
@@ -19,6 +19,7 @@ import (
 
 	"github.com/bep/simplecobra"
 	"github.com/gohugoio/hugo/common/hugo"
+	"github.com/spf13/cobra"
 )
 
 func newEnvCommand() simplecobra.Commander {
@@ -47,6 +48,9 @@ func newEnvCommand() simplecobra.Commander {
 			}
 			return nil
 		},
+		withc: func(cmd *cobra.Command, r *rootCommand) {
+			cmd.ValidArgsFunction = cobra.NoFileCompletions
+		},
 	}
 }
 
@@ -59,5 +63,8 @@ func newVersionCmd() simplecobra.Commander {
 		},
 		short: "Print Hugo version and environment info",
 		long:  "Print Hugo version and environment info. This is useful in Hugo bug reports.",
+		withc: func(cmd *cobra.Command, r *rootCommand) {
+			cmd.ValidArgsFunction = cobra.NoFileCompletions
+		},
 	}
 }
diff --git a/commands/gen.go b/commands/gen.go
index ae87091c4..88eb1b6fc 100644
--- a/commands/gen.go
+++ b/commands/gen.go
@@ -75,9 +75,13 @@ See https://xyproto.github.io/splash/docs/all.html for a preview of the availabl
 				return nil
 			},
 			withc: func(cmd *cobra.Command, r *rootCommand) {
+				cmd.ValidArgsFunction = cobra.NoFileCompletions
 				cmd.PersistentFlags().StringVar(&style, "style", "friendly", "highlighter style (see https://xyproto.github.io/splash/docs/)")
+				_ = cmd.RegisterFlagCompletionFunc("style", cobra.NoFileCompletions)
 				cmd.PersistentFlags().StringVar(&highlightStyle, "highlightStyle", "", "style used for highlighting lines (see https://github.com/alecthomas/chroma)")
+				_ = cmd.RegisterFlagCompletionFunc("highlightStyle", cobra.NoFileCompletions)
 				cmd.PersistentFlags().StringVar(&linesStyle, "linesStyle", "", "style used for line numbers (see https://github.com/alecthomas/chroma)")
+				_ = cmd.RegisterFlagCompletionFunc("linesStyle", cobra.NoFileCompletions)
 			},
 		}
 	}
@@ -115,9 +119,9 @@ See https://xyproto.github.io/splash/docs/all.html for a preview of the availabl
 				return nil
 			},
 			withc: func(cmd *cobra.Command, r *rootCommand) {
+				cmd.ValidArgsFunction = cobra.NoFileCompletions
 				cmd.PersistentFlags().StringVar(&genmandir, "dir", "man/", "the directory to write the man pages.")
-				// For bash-completion
-				cmd.PersistentFlags().SetAnnotation("dir", cobra.BashCompSubdirsInDir, []string{})
+				_ = cmd.MarkFlagDirname("dir")
 			},
 		}
 	}
@@ -172,9 +176,9 @@ url: %s
 				return nil
 			},
 			withc: func(cmd *cobra.Command, r *rootCommand) {
+				cmd.ValidArgsFunction = cobra.NoFileCompletions
 				cmd.PersistentFlags().StringVar(&gendocdir, "dir", "/tmp/hugodoc/", "the directory to write the doc.")
-				// For bash-completion
-				cmd.PersistentFlags().SetAnnotation("dir", cobra.BashCompSubdirsInDir, []string{})
+				_ = cmd.MarkFlagDirname("dir")
 			},
 		}
 	}
@@ -227,6 +231,7 @@ url: %s
 			},
 			withc: func(cmd *cobra.Command, r *rootCommand) {
 				cmd.Hidden = true
+				cmd.ValidArgsFunction = cobra.NoFileCompletions
 				cmd.PersistentFlags().StringVarP(&docsHelperTarget, "dir", "", "docs/data", "data dir")
 			},
 		}
diff --git a/commands/import.go b/commands/import.go
index 947b6d11f..c2d574aa1 100644
--- a/commands/import.go
+++ b/commands/import.go
@@ -58,6 +58,7 @@ Import from Jekyll requires two paths, e.g. ` + "`hugo import jekyll jekyll_root
 					return c.importFromJekyll(args)
 				},
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 					cmd.Flags().BoolVar(&c.force, "force", false, "allow import into non-empty target directory")
 				},
 			},
diff --git a/commands/list.go b/commands/list.go
index 8debe5ca5..b90a357f8 100644
--- a/commands/list.go
+++ b/commands/list.go
@@ -26,6 +26,7 @@ import (
 	"github.com/gohugoio/hugo/hugolib"
 	"github.com/gohugoio/hugo/resources/page"
 	"github.com/gohugoio/hugo/resources/resource"
+	"github.com/spf13/cobra"
 )
 
 // newListCommand creates a new list command and its subcommands.
@@ -102,6 +103,9 @@ func newListCommand() *listCommand {
 						"buildExpired", true,
 					)
 				},
+				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
+				},
 			},
 			&simpleCommand{
 				name:  "future",
@@ -119,6 +123,9 @@ func newListCommand() *listCommand {
 						"buildDrafts", true,
 					)
 				},
+				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
+				},
 			},
 			&simpleCommand{
 				name:  "expired",
@@ -136,6 +143,9 @@ func newListCommand() *listCommand {
 						"buildDrafts", true,
 					)
 				},
+				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
+				},
 			},
 			&simpleCommand{
 				name:  "all",
@@ -147,6 +157,9 @@ func newListCommand() *listCommand {
 					}
 					return list(cd, r, shouldInclude, "buildDrafts", true, "buildFuture", true, "buildExpired", true)
 				},
+				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
+				},
 			},
 		},
 	}
diff --git a/commands/mod.go b/commands/mod.go
index d64d2a983..7ff662944 100644
--- a/commands/mod.go
+++ b/commands/mod.go
@@ -62,6 +62,7 @@ removed from Hugo, but we need to test this out in "real life" to get a feel of
 so this may/will change in future versions of Hugo.
 `,
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 					applyLocalFlagsBuildConfig(cmd, r)
 				},
 				run: func(ctx context.Context, cd *simplecobra.Commandeer, r *rootCommand, args []string) error {
@@ -89,6 +90,7 @@ so this may/will change in future versions of Hugo.
 	inside a subfolder on GitHub, as one example.
 	`,
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 					applyLocalFlagsBuildConfig(cmd, r)
 				},
 				run: func(ctx context.Context, cd *simplecobra.Commandeer, r *rootCommand, args []string) error {
@@ -108,6 +110,7 @@ so this may/will change in future versions of Hugo.
 				short: "Verify dependencies.",
 				long:  `Verify checks that the dependencies of the current module, which are stored in a local downloaded source cache, have not been modified since being downloaded.`,
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 					applyLocalFlagsBuildConfig(cmd, r)
 					cmd.Flags().BoolVarP(&clean, "clean", "", false, "delete module cache for dependencies that fail verification")
 				},
@@ -127,6 +130,7 @@ so this may/will change in future versions of Hugo.
 Note that for vendored modules, that is the version listed and not the one from go.mod.
 `,
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 					applyLocalFlagsBuildConfig(cmd, r)
 					cmd.Flags().BoolVarP(&clean, "clean", "", false, "delete module cache for dependencies that fail verification")
 				},
@@ -144,8 +148,10 @@ Note that for vendored modules, that is the version listed and not the one from
 				short: "Delete the Hugo Module cache for the current project.",
 				long:  `Delete the Hugo Module cache for the current project.`,
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 					applyLocalFlagsBuildConfig(cmd, r)
 					cmd.Flags().StringVarP(&pattern, "pattern", "", "", `pattern matching module paths to clean (all if not set), e.g. "**hugo*"`)
+					_ = cmd.RegisterFlagCompletionFunc("pattern", cobra.NoFileCompletions)
 					cmd.Flags().BoolVarP(&all, "all", "", false, "clean entire module cache")
 				},
 				run: func(ctx context.Context, cd *simplecobra.Commandeer, r *rootCommand, args []string) error {
@@ -167,6 +173,7 @@ Note that for vendored modules, that is the version listed and not the one from
 				name:  "tidy",
 				short: "Remove unused entries in go.mod and go.sum.",
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 					applyLocalFlagsBuildConfig(cmd, r)
 				},
 				run: func(ctx context.Context, cd *simplecobra.Commandeer, r *rootCommand, args []string) error {
@@ -184,6 +191,7 @@ Note that for vendored modules, that is the version listed and not the one from
 	If a module is vendored, that is where Hugo will look for it's dependencies.
 	`,
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 					applyLocalFlagsBuildConfig(cmd, r)
 				},
 				run: func(ctx context.Context, cd *simplecobra.Commandeer, r *rootCommand, args []string) error {
@@ -225,6 +233,7 @@ Run "go help get" for more information. All flags available for "go get" is also
 ` + commonUsageMod,
 				withc: func(cmd *cobra.Command, r *rootCommand) {
 					cmd.DisableFlagParsing = true
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 				},
 				run: func(ctx context.Context, cd *simplecobra.Commandeer, r *rootCommand, args []string) error {
 					// We currently just pass on the flags we get to Go and
diff --git a/commands/new.go b/commands/new.go
index 79d2c9e7e..144da7cd7 100644
--- a/commands/new.go
+++ b/commands/new.go
@@ -24,6 +24,7 @@ import (
 	"github.com/gohugoio/hugo/config"
 	"github.com/gohugoio/hugo/create"
 	"github.com/gohugoio/hugo/create/skeletons"
+	"github.com/gohugoio/hugo/resources/kinds"
 	"github.com/spf13/cobra"
 )
 
@@ -60,8 +61,16 @@ Ensure you run this within the root directory of your site.`,
 					return create.NewContent(h, contentType, args[0], force)
 				},
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+						if len(args) != 0 {
+							return []string{}, cobra.ShellCompDirectiveNoFileComp
+						}
+						return []string{}, cobra.ShellCompDirectiveNoFileComp | cobra.ShellCompDirectiveFilterDirs
+					}
 					cmd.Flags().StringVarP(&contentType, "kind", "k", "", "content type to create")
+					_ = cmd.RegisterFlagCompletionFunc("kind", cobra.FixedCompletions(kinds.AllKindsInPages, cobra.ShellCompDirectiveNoFileComp))
 					cmd.Flags().String("editor", "", "edit new content with this editor, if provided")
+					_ = cmd.RegisterFlagCompletionFunc("editor", cobra.NoFileCompletions)
 					cmd.Flags().BoolVarP(&force, "force", "f", false, "overwrite file if it already exists")
 					applyLocalFlagsBuildConfig(cmd, r)
 				},
@@ -103,8 +112,15 @@ Use ` + "`hugo new [contentPath]`" + ` to create new content.`,
 					return nil
 				},
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+						if len(args) != 0 {
+							return []string{}, cobra.ShellCompDirectiveNoFileComp
+						}
+						return []string{}, cobra.ShellCompDirectiveNoFileComp | cobra.ShellCompDirectiveFilterDirs
+					}
 					cmd.Flags().BoolVarP(&force, "force", "f", false, "init inside non-empty directory")
 					cmd.Flags().StringVar(&format, "format", "toml", "preferred file format (toml, yaml or json)")
+					_ = cmd.RegisterFlagCompletionFunc("format", cobra.FixedCompletions([]string{"toml", "yaml", "json"}, cobra.ShellCompDirectiveNoFileComp))
 				},
 			},
 			&simpleCommand{
@@ -137,6 +153,9 @@ according to your needs.`,
 
 					return nil
 				},
+				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
+				},
 			},
 		},
 	}
diff --git a/commands/release.go b/commands/release.go
index 1d1aaad53..b05226d35 100644
--- a/commands/release.go
+++ b/commands/release.go
@@ -43,9 +43,11 @@ func newReleaseCommand() simplecobra.Commander {
 		},
 		withc: func(cmd *cobra.Command, r *rootCommand) {
 			cmd.Hidden = true
+			cmd.ValidArgsFunction = cobra.NoFileCompletions
 			cmd.PersistentFlags().BoolVarP(&skipPush, "skip-push", "", false, "skip pushing to remote")
 			cmd.PersistentFlags().BoolVarP(&try, "try", "", false, "no changes")
 			cmd.PersistentFlags().IntVarP(&step, "step", "", 0, "step to run (1: set new version 2: prepare next dev version)")
+			_ = cmd.RegisterFlagCompletionFunc("step", cobra.FixedCompletions([]string{"1", "2"}, cobra.ShellCompDirectiveNoFileComp))
 		},
 	}
 }
diff --git a/commands/server.go b/commands/server.go
index 870283bba..09fb4e79f 100644
--- a/commands/server.go
+++ b/commands/server.go
@@ -123,6 +123,7 @@ func newServerCommand() *serverCommand {
 					return mclib.RunMain()
 				},
 				withc: func(cmd *cobra.Command, r *rootCommand) {
+					cmd.ValidArgsFunction = cobra.NoFileCompletions
 					cmd.Flags().BoolVar(&uninstall, "uninstall", false, "Uninstall the local CA (but do not delete it).")
 				},
 			},
@@ -523,10 +524,15 @@ of a second, you will be able to save and see your changes nearly instantly.`
 	cmd.Aliases = []string{"serve"}
 
 	cmd.Flags().IntVarP(&c.serverPort, "port", "p", 1313, "port on which the server will listen")
+	_ = cmd.RegisterFlagCompletionFunc("port", cobra.NoFileCompletions)
 	cmd.Flags().IntVar(&c.liveReloadPort, "liveReloadPort", -1, "port for live reloading (i.e. 443 in HTTPS proxy situations)")
+	_ = cmd.RegisterFlagCompletionFunc("liveReloadPort", cobra.NoFileCompletions)
 	cmd.Flags().StringVarP(&c.serverInterface, "bind", "", "127.0.0.1", "interface to which the server will bind")
+	_ = cmd.RegisterFlagCompletionFunc("bind", cobra.NoFileCompletions)
 	cmd.Flags().StringVarP(&c.tlsCertFile, "tlsCertFile", "", "", "path to TLS certificate file")
+	_ = cmd.MarkFlagFilename("tlsCertFile", "pem")
 	cmd.Flags().StringVarP(&c.tlsKeyFile, "tlsKeyFile", "", "", "path to TLS key file")
+	_ = cmd.MarkFlagFilename("tlsKeyFile", "pem")
 	cmd.Flags().BoolVar(&c.tlsAuto, "tlsAuto", false, "generate and use locally-trusted certificates.")
 	cmd.Flags().BoolVar(&c.pprof, "pprof", false, "enable the pprof server (port 8080)")
 	cmd.Flags().BoolVarP(&c.serverWatch, "watch", "w", true, "watch filesystem for changes and recreate as needed")
@@ -538,9 +544,6 @@ of a second, you will be able to save and see your changes nearly instantly.`
 	cmd.Flags().BoolVar(&c.disableFastRender, "disableFastRender", false, "enables full re-renders on changes")
 	cmd.Flags().BoolVar(&c.disableBrowserError, "disableBrowserError", false, "do not show build errors in the browser")
 
-	cmd.Flags().SetAnnotation("tlsCertFile", cobra.BashCompSubdirsInDir, []string{})
-	cmd.Flags().SetAnnotation("tlsKeyFile", cobra.BashCompSubdirsInDir, []string{})
-
 	r := cd.Root.Command.(*rootCommand)
 	applyLocalFlagsBuild(cmd, r)