Add empty-key check to mlr check

docs/src/manpage.md

@@ -936,8 +936,11 @@ MILLER(1)                                                            MILLER(1)
 
    1mcheck0m
        Usage: mlr check [options]
-       Consumes records without printing any output.
+       Consumes records without printing any output,
        Useful for doing a well-formatted check on input data.
+       with the exception that warnings are printed to stderr.
+       Current checks are:
+       * If any key is the empty string
        Options:
        -h|--help Show this message.
 
@@ -1212,13 +1215,13 @@ MILLER(1)                                                            MILLER(1)
        Note that "mlr filter" is more powerful, but requires you to know field names.
        By contrast, "mlr grep" allows you to regex-match the entire record. It does this
        by formatting each record in memory as DKVP (or NIDX, if -a is supplied), using
-       command-line-specified ORS/OFS/OPS, and matching the resulting line against the
-       regex specified here. In particular, the regex is not applied to the input
-       stream: if you have CSV with header line "x,y,z" and data line "1,2,3" then the
-       regex will be matched, not against either of these lines, but against the DKVP
-       line "x=1,y=2,z=3".  Furthermore, not all the options to system grep are
-       supported, and this command is intended to be merely a keystroke-saver. To get
-       all the features of system grep, you can do
+       OFS "," and OPS "=", and matching the resulting line against the regex specified
+       here. In particular, the regex is not applied to the input stream: if you have
+       CSV with header line "x,y,z" and data line "1,2,3" then the regex will be
+       matched, not against either of these lines, but against the DKVP line
+       "x=1,y=2,z=3".  Furthermore, not all the options to system grep are supported,
+       and this command is intended to be merely a keystroke-saver. To get all the
+       features of system grep, you can do
          "mlr --odkvp ... | grep ... | mlr --idkvp ..."
 
    1mgroup-by0m
@@ -3430,5 +3433,5 @@ MILLER(1)                                                            MILLER(1)
 
 
 
-                                  2023-06-24                         MILLER(1)
+                                  2023-06-25                         MILLER(1)
 </pre>

docs/src/manpage.txt

@@ -915,8 +915,11 @@ MILLER(1)                                                            MILLER(1)
 
    1mcheck0m
        Usage: mlr check [options]
-       Consumes records without printing any output.
+       Consumes records without printing any output,
        Useful for doing a well-formatted check on input data.
+       with the exception that warnings are printed to stderr.
+       Current checks are:
+       * If any key is the empty string
        Options:
        -h|--help Show this message.
 
@@ -1191,13 +1194,13 @@ MILLER(1)                                                            MILLER(1)
        Note that "mlr filter" is more powerful, but requires you to know field names.
        By contrast, "mlr grep" allows you to regex-match the entire record. It does this
        by formatting each record in memory as DKVP (or NIDX, if -a is supplied), using
-       command-line-specified ORS/OFS/OPS, and matching the resulting line against the
-       regex specified here. In particular, the regex is not applied to the input
-       stream: if you have CSV with header line "x,y,z" and data line "1,2,3" then the
-       regex will be matched, not against either of these lines, but against the DKVP
-       line "x=1,y=2,z=3".  Furthermore, not all the options to system grep are
-       supported, and this command is intended to be merely a keystroke-saver. To get
-       all the features of system grep, you can do
+       OFS "," and OPS "=", and matching the resulting line against the regex specified
+       here. In particular, the regex is not applied to the input stream: if you have
+       CSV with header line "x,y,z" and data line "1,2,3" then the regex will be
+       matched, not against either of these lines, but against the DKVP line
+       "x=1,y=2,z=3".  Furthermore, not all the options to system grep are supported,
+       and this command is intended to be merely a keystroke-saver. To get all the
+       features of system grep, you can do
          "mlr --odkvp ... | grep ... | mlr --idkvp ..."
 
    1mgroup-by0m
@@ -3409,4 +3412,4 @@ MILLER(1)                                                            MILLER(1)
 
 
 
-                                  2023-06-24                         MILLER(1)
+                                  2023-06-25                         MILLER(1)

docs/src/reference-verbs.md

@@ -376,8 +376,11 @@ n a   b   i x        y
 </pre>
 <pre class="pre-non-highlight-in-pair">
 Usage: mlr check [options]
-Consumes records without printing any output.
+Consumes records without printing any output,
 Useful for doing a well-formatted check on input data.
+with the exception that warnings are printed to stderr.
+Current checks are:
+* If any key is the empty string
 Options:
 -h|--help Show this message.
 </pre>
@@ -1355,13 +1358,13 @@ Options:
 Note that "mlr filter" is more powerful, but requires you to know field names.
 By contrast, "mlr grep" allows you to regex-match the entire record. It does this
 by formatting each record in memory as DKVP (or NIDX, if -a is supplied), using
-command-line-specified ORS/OFS/OPS, and matching the resulting line against the
-regex specified here. In particular, the regex is not applied to the input
-stream: if you have CSV with header line "x,y,z" and data line "1,2,3" then the
-regex will be matched, not against either of these lines, but against the DKVP
-line "x=1,y=2,z=3".  Furthermore, not all the options to system grep are
-supported, and this command is intended to be merely a keystroke-saver. To get
-all the features of system grep, you can do
+OFS "," and OPS "=", and matching the resulting line against the regex specified
+here. In particular, the regex is not applied to the input stream: if you have
+CSV with header line "x,y,z" and data line "1,2,3" then the regex will be
+matched, not against either of these lines, but against the DKVP line
+"x=1,y=2,z=3".  Furthermore, not all the options to system grep are supported,
+and this command is intended to be merely a keystroke-saver. To get all the
+features of system grep, you can do
   "mlr --odkvp ... | grep ... | mlr --idkvp ..."
 </pre>
 

internal/pkg/transformers/check.go

@@ -24,8 +24,12 @@ func transformerCheckUsage(
 	o *os.File,
 ) {
 	fmt.Fprintf(o, "Usage: %s %s [options]\n", "mlr", verbNameCheck)
-	fmt.Fprintf(o, "Consumes records without printing any output.\n")
+	fmt.Fprintf(o, "Consumes records without printing any output,\n")
 	fmt.Fprintf(o, "Useful for doing a well-formatted check on input data.\n")
+	fmt.Fprintf(o, "with the exception that warnings are printed to stderr.\n")
+	fmt.Fprintf(o, "Current checks are:\n")
+	fmt.Fprintf(o, "* Data are parseable\n")
+	fmt.Fprintf(o, "* If any key is the empty string\n")
 	fmt.Fprintf(o, "Options:\n")
 	fmt.Fprintf(o, "-h|--help Show this message.\n")
 }
@@ -79,10 +83,13 @@ func transformerCheckParseCLI(
 // ----------------------------------------------------------------
 type TransformerCheck struct {
 	// stateless
+	messagedReEmptyKey map[string]bool
 }
 
 func NewTransformerCheck() (*TransformerCheck, error) {
-	return &TransformerCheck{}, nil
+	return &TransformerCheck{
+		messagedReEmptyKey: make(map[string]bool),
+	}, nil
 }
 
 func (tr *TransformerCheck) Transform(
@@ -92,7 +99,27 @@ func (tr *TransformerCheck) Transform(
 	outputDownstreamDoneChannel chan<- bool,
 ) {
 	HandleDefaultDownstreamDone(inputDownstreamDoneChannel, outputDownstreamDoneChannel)
-	if inrecAndContext.EndOfStream {
+	if !inrecAndContext.EndOfStream {
+		inrec := inrecAndContext.Record
+		for pe := inrec.Head; pe != nil; pe = pe.Next {
+			if pe.Key == "" {
+				context := inrecAndContext.Context
+
+				// Most Miller users are CSV users. And for CSV this will be an error on
+				// *every* record, or none -- so let's not print this multiple times.
+				if tr.messagedReEmptyKey[context.FILENAME] {
+					continue
+				}
+
+				message := fmt.Sprintf(
+					"mlr: warning: empty-string key at filename %s record number %d",
+					context.FILENAME, context.NR,
+				)
+				fmt.Fprintln(os.Stderr, message)
+				tr.messagedReEmptyKey[context.FILENAME] = true
+			}
+		}
+	} else {
 		outputRecordsAndContexts.PushBack(inrecAndContext)
 	}
 }

man/manpage.txt

@@ -915,8 +915,11 @@ MILLER(1)                                                            MILLER(1)
 
    1mcheck0m
        Usage: mlr check [options]
-       Consumes records without printing any output.
+       Consumes records without printing any output,
        Useful for doing a well-formatted check on input data.
+       with the exception that warnings are printed to stderr.
+       Current checks are:
+       * If any key is the empty string
        Options:
        -h|--help Show this message.
 
@@ -1191,13 +1194,13 @@ MILLER(1)                                                            MILLER(1)
        Note that "mlr filter" is more powerful, but requires you to know field names.
        By contrast, "mlr grep" allows you to regex-match the entire record. It does this
        by formatting each record in memory as DKVP (or NIDX, if -a is supplied), using
-       command-line-specified ORS/OFS/OPS, and matching the resulting line against the
-       regex specified here. In particular, the regex is not applied to the input
-       stream: if you have CSV with header line "x,y,z" and data line "1,2,3" then the
-       regex will be matched, not against either of these lines, but against the DKVP
-       line "x=1,y=2,z=3".  Furthermore, not all the options to system grep are
-       supported, and this command is intended to be merely a keystroke-saver. To get
-       all the features of system grep, you can do
+       OFS "," and OPS "=", and matching the resulting line against the regex specified
+       here. In particular, the regex is not applied to the input stream: if you have
+       CSV with header line "x,y,z" and data line "1,2,3" then the regex will be
+       matched, not against either of these lines, but against the DKVP line
+       "x=1,y=2,z=3".  Furthermore, not all the options to system grep are supported,
+       and this command is intended to be merely a keystroke-saver. To get all the
+       features of system grep, you can do
          "mlr --odkvp ... | grep ... | mlr --idkvp ..."
 
    1mgroup-by0m
@@ -3409,4 +3412,4 @@ MILLER(1)                                                            MILLER(1)
 
 
 
-                                  2023-06-24                         MILLER(1)
+                                  2023-06-25                         MILLER(1)

man/mlr.1

@@ -2,12 +2,12 @@
 .\"     Title: mlr
 .\"    Author: [see the "AUTHOR" section]
 .\" Generator: ./mkman.rb
-.\"      Date: 2023-06-24
+.\"      Date: 2023-06-25
 .\"    Manual: \ \&
 .\"    Source: \ \&
 .\"  Language: English
 .\"
-.TH "MILLER" "1" "2023-06-24" "\ \&" "\ \&"
+.TH "MILLER" "1" "2023-06-25" "\ \&" "\ \&"
 .\" -----------------------------------------------------------------
 .\" * Portability definitions
 .\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -1122,8 +1122,11 @@ Options:
 .\}
 .nf
 Usage: mlr check [options]
-Consumes records without printing any output.
+Consumes records without printing any output,
 Useful for doing a well-formatted check on input data.
+with the exception that warnings are printed to stderr.
+Current checks are:
+* If any key is the empty string
 Options:
 -h|--help Show this message.
 .fi
@@ -1482,13 +1485,13 @@ Options:
 Note that "mlr filter" is more powerful, but requires you to know field names.
 By contrast, "mlr grep" allows you to regex-match the entire record. It does this
 by formatting each record in memory as DKVP (or NIDX, if -a is supplied), using
-command-line-specified ORS/OFS/OPS, and matching the resulting line against the
-regex specified here. In particular, the regex is not applied to the input
-stream: if you have CSV with header line "x,y,z" and data line "1,2,3" then the
-regex will be matched, not against either of these lines, but against the DKVP
-line "x=1,y=2,z=3".  Furthermore, not all the options to system grep are
-supported, and this command is intended to be merely a keystroke-saver. To get
-all the features of system grep, you can do
+OFS "," and OPS "=", and matching the resulting line against the regex specified
+here. In particular, the regex is not applied to the input stream: if you have
+CSV with header line "x,y,z" and data line "1,2,3" then the regex will be
+matched, not against either of these lines, but against the DKVP line
+"x=1,y=2,z=3".  Furthermore, not all the options to system grep are supported,
+and this command is intended to be merely a keystroke-saver. To get all the
+features of system grep, you can do
   "mlr --odkvp ... | grep ... | mlr --idkvp ..."
 .fi
 .if n \{\

test/cases/cli-help/0001/expout

@@ -63,8 +63,12 @@ Options:
 ================================================================
 check
 Usage: mlr check [options]
-Consumes records without printing any output.
+Consumes records without printing any output,
 Useful for doing a well-formatted check on input data.
+with the exception that warnings are printed to stderr.
+Current checks are:
+* Data are parseable
+* If any key is the empty string
 Options:
 -h|--help Show this message.
 

test/cases/verb-check/0001/cmd

@@ -0,0 +1 @@
+mlr --csv check ${CASEDIR}/input.csv

test/cases/verb-check/0001/input.csv

@@ -0,0 +1,3 @@
+a,b,c
+1,2,3
+4,5,6

test/cases/verb-check/0002/cmd

@@ -0,0 +1 @@
+mlr --csv check ${CASEDIR}/input.csv

test/cases/verb-check/0002/experr

@@ -0,0 +1 @@
+mlr: warning: empty-string key at filename test/cases/verb-check/0002/input.csv record number 1

test/cases/verb-check/0002/input.csv

@@ -0,0 +1,3 @@
+a,,c
+1,2,3
+4,5,6