mcfg: centralize logic for fuzzy parsing strings, use it to implement SourceMap

mcfg/cli.go

@@ -1,7 +1,6 @@
 package mcfg
 
 import (
-	"encoding/json"
 	"fmt"
 	"io"
 	"os"
@@ -23,6 +22,11 @@ import (
 // stdout and the process will exit. Since all normally-defined parameters must
 // being with double-dash ("--") they won't ever conflict with the help option.
 //
+// SourceCLI behaves a little differently with boolean parameters. Setting the
+// value of a boolean parameter directly _must_ be done with an equals, for
+// example: `--boolean-flag=1` or `--boolean-flag=false`. Using the
+// space-separated format will not work. If a boolean has no equal-separated
+// value it is assumed to be setting the value to `true`, as would be expected.
 type SourceCLI struct {
 	Args []string // if nil then os.Args[1:] is used
 
@@ -86,27 +90,20 @@ func (cli SourceCLI) Parse(cfg *Cfg) ([]ParamValue, error) {
 
 		// pvOk is always true at this point, and so pv is filled in
 
-		if pv.IsBool {
+		// As a special case for CLI, if a boolean has no value set it means it
-			// if it's a boolean we don't expect there to be a following value,
+		// is true.
-			// it's just a flag
+		if pv.IsBool && !pvStrValOk {
-			if pvStrValOk {
+			pvStrVal = "true"
-				return nil, fmt.Errorf("param %q is a boolean and cannot have a value", arg)
+			pvStrValOk = true
-			}
-			pv.Value = json.RawMessage("true")
-
 		} else if !pvStrValOk {
 			// everything else should have a value. if pvStrVal isn't filled it
 			// means the next arg should be one. Continue the loop, it'll get
 			// filled with the next one (hopefully)
 			continue
-
-		} else if pv.IsString && (pvStrVal == "" || pvStrVal[0] != '"') {
-			pv.Value = json.RawMessage(`"` + pvStrVal + `"`)
-
-		} else {
-			pv.Value = json.RawMessage(pvStrVal)
 		}
 
+		pv.Value = fuzzyParse(pv.Param, pvStrVal)
+
 		pvs = append(pvs, pv)
 		key = ""
 		pv = ParamValue{}

mcfg/env.go

@@ -1,7 +1,6 @@
 package mcfg
 
 import (
-	"encoding/json"
 	"fmt"
 	"os"
 	"strings"
@@ -58,18 +57,7 @@ func (env SourceEnv) Parse(cfg *Cfg) ([]ParamValue, error) {
 		}
 		k, v := split[0], split[1]
 		if pv, ok := pvM[k]; ok {
-			if pv.IsBool {
+			pv.Value = fuzzyParse(pv.Param, v)
-				if v == "" {
-					pv.Value = json.RawMessage("false")
-				} else {
-					pv.Value = json.RawMessage("true")
-				}
-			} else if pv.IsString && (v == "" || v[0] != '"') {
-				pv.Value = json.RawMessage(`"` + v + `"`)
-
-			} else {
-				pv.Value = json.RawMessage(v)
-			}
 			pvs = append(pvs, pv)
 		}
 	}

mcfg/param.go

@@ -95,6 +95,11 @@ func (c *Cfg) ParamRequiredString(name, usage string) *string {
 
 // ParamBool returns a *bool which will be populated once the Cfg is run, and
 // which defaults to false if unconfigured
+//
+// The default behavior of all Sources is that a boolean parameter will be set
+// to true unless the value is "", 0, or false. In the case of the CLI Source
+// the value will also be true when the parameter is used with no value at all,
+// as would be expected.
 func (c *Cfg) ParamBool(name, usage string) *bool {
 	var b bool
 	c.ParamAdd(Param{Name: name, Usage: usage, IsBool: true, Into: &b})

mcfg/source.go

@@ -8,6 +8,22 @@ import (
 	"strings"
 )
 
+func fuzzyParse(p Param, v string) json.RawMessage {
+	if p.IsBool {
+		if v == "" || v == "0" || v == "false" {
+			return json.RawMessage("false")
+		}
+		return json.RawMessage("true")
+
+	} else if p.IsString && (v == "" || v[0] != '"') {
+		return json.RawMessage(`"` + v + `"`)
+	}
+
+	return json.RawMessage(v)
+}
+
+// TODO moving Path into Param would make a lot more sense
+
 // ParamValue describes a value for a parameter which has been parsed by a
 // Source
 type ParamValue struct {
@@ -69,3 +85,20 @@ func (ss Sources) Parse(c *Cfg) ([]ParamValue, error) {
 	}
 	return pvs, nil
 }
+
+// SourceMap implements the Source interface by mapping parameter names to
+// values for them. The names are comprised of the path and name of a Param
+// joined by "-" characters, i.e. `strings.Join(append(p.Path, p.Name), "-")`.
+// Values will be parsed in the same way that SourceEnv parses its variables.
+type SourceMap map[string]string
+
+func (m SourceMap) Parse(c *Cfg) ([]ParamValue, error) {
+	pvs := make([]ParamValue, 0, len(m))
+	for _, pv := range c.allParamValues() {
+		if v, ok := m[pv.displayName()]; ok {
+			pv.Value = fuzzyParse(pv.Param, v)
+			pvs = append(pvs, pv)
+		}
+	}
+	return pvs, nil
+}

mcfg/source_test.go

@@ -159,3 +159,23 @@ func TestSources(t *T) {
 		massert.Equal(3, *c),
 	))
 }
+
+func TestSourceMap(t *T) {
+	cfg := New()
+	a := cfg.ParamRequiredInt("a", "")
+	foo := cfg.Child("foo")
+	b := foo.ParamRequiredString("b", "")
+	c := foo.ParamBool("c", "")
+
+	err := cfg.populateParams(SourceMap{
+		"a":     "4",
+		"foo-b": "bbb",
+		"foo-c": "1",
+	})
+	massert.Fatal(t, massert.All(
+		massert.Nil(err),
+		massert.Equal(4, *a),
+		massert.Equal("bbb", *b),
+		massert.Equal(true, *c),
+	))
+}